Difference between revisions of "High Intensity Interval Training"

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[[File:Sprinter.jpg|right|thumb|400px|To run HIIT intervals requires a longer stride length, so other modes, such as a stationary bike may be more appropriate.]]
 
[[File:Sprinter.jpg|right|thumb|400px|To run HIIT intervals requires a longer stride length, so other modes, such as a stationary bike may be more appropriate.]]
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High Intensity Interval Training (HIIT) uses repeated short periods of very intense cardiovascular exercise separated by lower intensity recoveries. HIIT has been shown to improve aerobic capacity in untrained and moderately active individuals more quickly than Continuous Moderate Exercise, as well as having potential benefits for highly trained athletes. HIIT has also been shown to reduce body fat in untrained people more effectively than Continuous Moderate Exercise. However, there is no evidence to suggest that HIIT can replace other forms of training for endurance races.  
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{{DISPLAYTITLE:High Intensity Interval Training (HIIT) Tabata and Wingate}}
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HIIT can be highly effective training, but involves a risk of injury. HIIT has been shown to improve aerobic capacity in untrained and moderately active individuals more quickly than Continuous Moderate Exercise, as well as having potential benefits for highly trained athletes. HIIT has also been shown to reduce body fat in untrained people more effectively than Continuous Moderate Exercise. However, there is no evidence to suggest that HIIT can replace other forms of training for endurance races. High Intensity Interval Training (HIIT) uses repeated short periods of very intense cardiovascular exercise separated by lower intensity recoveries. (I've found the [[Stryd]] estimate of power output is the best approach to gauging effort during HIIT, though [[Moxy]] can provide some interesting insight from [[Muscle Oxygen Saturation]].)
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If you'd like to know more about the science behind HIIT, see [[The Science of High Intensity Interval Training]].
 
=What is HIIT?=
 
=What is HIIT?=
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High Intensity Interval Training is a form of [[Introduction to Interval Training| Interval Training]] using short intervals of 10 seconds to 5 minutes at an intensity at or above 90% [[VO2max|V?O<sub>2</sub>max]]<ref name="Boutcher2011"/>. High Intensity Interval Training, abbreviated to HIIT or HIT, is sometimes called High-Intensity Intermittent Exercise<ref name="Trapp-2008"/> or Sprint Training<ref name="Gibala-2006"/>.
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High Intensity Interval Training is a form of [[Introduction to Interval Training| Interval Training]] using short intervals of 10 seconds to 5 minutes at an intensity at or above 90% [[VO2max|V̇O<sub>2</sub>max]]<ref name="Boutcher2011"/>. High Intensity Interval Training, abbreviated to HIIT or HIT, is sometimes called High-Intensity Intermittent Exercise<ref name="Trapp-2008"/> or Sprint Training<ref name="Gibala-2006"/>.
 
=HIIT Recommendations=
 
=HIIT Recommendations=
 
Below are my recommendations based on my interpretation of the available evidence. These recommendations for incorporating HIIT in your training depend on your current fitness goals.
 
Below are my recommendations based on my interpretation of the available evidence. These recommendations for incorporating HIIT in your training depend on your current fitness goals.
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* To reduce injury risk, I strongly recommend performing HIIT on a stationary bike trainer rather than running. See "HIIT Training Methods" below for details.
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* Ease into HIIT gently, following [[Safe Speedwork]] recommendations.
 
* For sedentary people, HIIT is probably more effective in building initial fitness than Continuous Moderate Exercise. Three sessions per week of [[#Wingate| Wingate]] HIIT on a stationary bike should provide an improvement in fitness for a modest time commitment. Using [[#WinTab| WinTab]] style HIIT may produce similar benefits for a lower time commitment.  
 
* For sedentary people, HIIT is probably more effective in building initial fitness than Continuous Moderate Exercise. Three sessions per week of [[#Wingate| Wingate]] HIIT on a stationary bike should provide an improvement in fitness for a modest time commitment. Using [[#WinTab| WinTab]] style HIIT may produce similar benefits for a lower time commitment.  
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* For people looking to lose weight, HIIT will probably produce a greater reduction in body fat than Continuous Moderate Exercise. Three sessions per week of Wingate HIIT on a stationary bike should help with weight loss and appetite control. The HIIT could be combined with other forms of exercise on the other days, which may further improve weight loss. (HIIT probably more effective than Continuous Moderate Exercise at improving insulin sensitivity.)
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* For people looking to lose weight, HIIT will probably produce a greater reduction in body fat than Continuous Moderate Exercise. Three sessions per week of [[Cycling HIIT For Runners | Wingate HIIT on a stationary bike]] should help with [[Weight Loss]] and appetite control. The HIIT could be combined with other forms of exercise on the other days, which may further improve weight loss. (HIIT probably more effective than Continuous Moderate Exercise at improving insulin sensitivity.)
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* Recreationally active people looking for rounded fitness may benefit from including HIIT in their overall training program. Adding 1-3 sessions per week of Wingate or WinTab HIIT on a stationary bike should provide an improvement in fitness.
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* Recreationally active people looking for rounded fitness may benefit from including HIIT in their overall training program. Adding 1-3 sessions per week of [[Cycling HIIT For Runners| Wingate or WinTab HIIT on a stationary bike]] should provide an improvement in fitness.  
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* Athletes focused on improving their performance in endurance races lasting less than an hour will probably benefit from replacing some of their training load with a combination of both traditional HIIT and shorter Wingate or WinTab style HIIT. Up to one traditional HIIT or 1-3 shorter HIIT sessions could be included in a weekly training routine. Care should be taken to increase [[TRIMP| Training Load]] slowly with the additional HIIT and try to avoid increasing [[Training Monotony]]. The traditional HIIT should be performed by running on a track or other outdoor location. For the shorter HIIT, a stationary bike probably has a lower injury risk, but the additional benefits of outdoor running may outweigh the additional injury risk. However, the fast paces of the shorter HIIT should be introduced gradually, building up the pace over a number of workouts.  
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* Athletes focused on improving their performance in endurance races lasting less than an hour will probably benefit from replacing some of their training load with a combination of both traditional HIIT and shorter Wingate or WinTab style HIIT. Up to one traditional HIIT or 1-3 shorter HIIT sessions could be included in a weekly training routine. Care should be taken to increase [[TRIMP| Training Load]] slowly with the additional HIIT and try to avoid increasing [[Training Monotony]]. The traditional HIIT should be performed by running on a track or other outdoor location. For the shorter HIIT, a stationary bike probably has a lower injury risk, but the additional benefits of outdoor running may outweigh the additional injury risk. However, the fast paces of the shorter HIIT should be introduced gradually, building up the pace over a number of workouts. See [[Cycling HIIT For Runners]] for details.  
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* There is no direct evidence to indicate if HIIT will help athletes focused on improving their performance in events lasting longer than an hour. However, it seems reasonable that HIIT would provide some benefits. Including 1 or 2 Wingate or WinTab HIIT sessions per week may be appropriate. As noted in the prior bullet point for shorter duration athletes, care should be taken to monitor [[TRIMP| Training Load]] and [[Training Monotony]]. As with athletes focusing on events lasting less than an hour, the stationary bike has the lowest injury risk, but there may be benefits to other training modes. However, athletes competing in longer duration events typically don't have the same need for the very high paces that are sometimes seen at the end of shorter events.
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* There is no direct evidence to indicate if HIIT will help athletes focused on improving their performance in events lasting longer than an hour. However, it seems reasonable that HIIT would provide some benefits. Including 1 or 2 Wingate or WinTab HIIT sessions per week may be appropriate. Using HIIT followed immediately by endurance training may mimic some of the effects of longer training. As noted in the prior bullet point for shorter duration athletes, care should be taken to monitor [[TRIMP| Training Load]] and [[Training Monotony]]. As with athletes focusing on events lasting less than an hour, the stationary bike has the lowest injury risk, but there may be benefits to other training modes. However, athletes competing in longer duration events typically don't have the same need for the very high paces that are sometimes seen at the end of shorter events.
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* There is no evidence to suggest that HIIT can be used to replace Continuous Moderate Exercise such as the Long Run that is a core part of endurance training.  
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* There is no evidence to suggest that HIIT can be used to replace Continuous Moderate Exercise such as the [[Long Run]] that is a core part of endurance training.  
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* HIIT can rapidly deplete [[Glycogen stores]], creating the possibility of using HIIT followed by lower intensity endurance training to mimic the effects of a much longer training session.
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* While Glycogen stores are restored fairly quickly afterward, it seems like much of that may come from breaking down muscle protein. For the research behind this, see [[Glycogen#Glycogen_Depletion_and_HIIT| Glycogen Depletion and HIIT]]. Taking in calories in the form of carbohydrate and protein very soon after HIIT will help prevent muscle loss.
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* For "all out" intensities, fewer intervals may be more effective. In my experience, 2 intervals, win the second at a slightly lower resistance (slope on the bike) is optimum for reaching and maintaining the highest workloads.
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=Incorporating HIIT In Your Training Regime =
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Here are some suggestions for adding HIIT to your training. These are not hard and fast rules, as there is a lot of individual variability.
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* HIIT sessions should be considered hard workouts, so don't try to replace easy or rest days with HIIT while leaving your hard training as is.
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* If your existing training is not already structured around hard days interspersed with rest days, then HIIT should be distributed through the week and you should take it easier on other days.
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* If you are already structuring your workouts around hard days, you should replace a hard workout with HIIT rather than adding to your workload. (Monitoring your [[Training Monotony]] may help prevent [[Overtraining]].)
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* If you're looking to increase your training load, then HIIT may be an option. I would recommend starting off by replacing a hard workout with HIIT, then adding the original workload back over time. Remember that it can take several weeks for the additional fatigue to manifest itself, as fatigue builds up over a remarkably long time.
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* One approach to using HIIT to increase your workload would be to incorporate a HIIT workout with a moderate length long run. There's not much evidence to know the optimum approach, or how this might change the effectiveness of HIIT. It seems likely that the HIIT would create additional fatigue and [[Glycogen| Glycogen Depletion]], which would make the run seem much longer than the distance would suggest. For instance, a 16 mile moderately long run could be replaced by a HIIT and 10 miles. The exact details are going to be quite individual, so experiment based on feeling.
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* Another way of increasing your training load via HIIT would be to use the HIIT workout as a second workout on a hard day. This may be of particular value if you're [[How Often To Run| only running 3-4 days per week]] (as I recommend.)
 
=Types of HIIT=
 
=Types of HIIT=
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There are various different protocols for performing HIIT. While the [[Tabata]] is probably the most widely recognized name in HIIT, it is one of the least studied and the least used.  
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There are various different protocols for performing HIIT. While the Tabata is probably the most widely recognized name in HIIT, it is one of the least studied and the least used.  
 
==Tabata==
 
==Tabata==
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{{Main|Tabata}}
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''Main article: [[Tabata]]''
  
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The [[Tabata]] workout is one of the best known protocols for HIIT and consists of 7-8 repeats of 20 seconds at 170% of [[VO2max|V?O<sub>2</sub>max]] with 10 seconds rest. The number of repetitions is defined by how long the required intensity can be maintained. An athlete should be able to complete 7-8 intervals; if 9 can be performed, the intensity is increased. However, few people actually follow the [[Tabata]] protocol because it requires specialist equipment to measure [[VO2max|V?O<sub>2</sub>max]], then calculate 1.7x the [[VO2max|V?O<sub>2</sub>max]] workload that should be used. In practice, most people do what I call the WinTab workout (see below).  
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The [[Tabata]] workout is one of the best-known protocols for HIIT and consists of 7-8 repeats of 20 seconds at 170% of [[VO2max|V̇O<sub>2</sub>max]] with 10 seconds rest. The number of repetitions is defined by how long the required intensity can be maintained. An athlete should be able to complete 7-8 intervals; if 9 can be performed, the intensity is increased. However, few people actually follow the [[Tabata]] protocol because it requires specialist equipment to measure [[VO2max|V̇O<sub>2</sub>max]], then calculate 1.7x the [[VO2max|V̇O<sub>2</sub>max]] workload that should be used. In practice, most people do what I call the WinTab workout (see below).
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==4 x 4 (The Norwegian Method)==
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''Main article: [[Medium Intensity High Volume Intervals]]''
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The original Norwegian Method is to perform four intervals, each of four minutes at 90-95% of maximum heart rate, with 3-minute recoveries, often called "4x4". At first glance this appears to be an odd specification, as it's impossible to immediately increase your heart rate to 90% of maximum, and the original definition<ref name="Helgerud-2007"/> talks about trying to get your heart rate to 90% or above in 60-90 seconds, then adjust the effort to keep your heart rate in range. This approach was refined by a more detailed study<ref name="Acala Roche-Willis Astorino 2020"/> that used a range of 85-95% of max heart rate. In that study, the subjects increased their effort rapidly to 85-100% of the effort for their [[VO2max|VO<sub>2</sub>max]]. After their heart rate reached 95% of max, the effort was reduced to keep it in the 85-95% range. What's that mean in practice? Given the details below, you need to estimate your [[VO2max|VO<sub>2</sub>max]], then either work out your pace or power.
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* '''Power'''. Use the formula "weight in Kg * [[VO2max|VO<sub>2</sub>max]] * 0.097". You then start the 4-minute interval at 85-100% of that power.
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* '''Pace'''. Luckily, it happens that pace in meters/second is roughly the same as power in watts/Kg. So you can use the formula to "[[VO2max|VO<sub>2</sub>max]] * 0.097" to estimate your target pace in meters/second, then use an online converter to change that to min/mile or min/Km.
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Dropping your effort as the interval progresses may result in a surprisingly large reduction, with the study showing that that most intervals ended at about 60% of the initial power. The study also showed that the second through fourth interval had a lower initial power requirement, roughly 10-15% lower than the first interval.
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Remember, you can estimate your [[VO2max|VO<sub>2</sub>max]] from a race performance using a [[Running Calculator]].
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(Note that the more recent versions of the Norwegian Method use [[Medium Intensity High Volume Intervals]].)
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===4x4 Conversion Details===
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The study had athletes with average [[VO2max|VO<sub>2</sub>max]] of 37, average weight of 72 Kg, and average peak power output of 260w, which is 3.6 w/Kg. A [[Stryd]] based study<ref name="stryd"/> showed that there's a linear relationship between [[VO2max|VO<sub>2</sub>max]] and peak power.  (Peak power at [[VO2max|VO<sub>2</sub>max]] varies with protocol). For this study, the peak power in w/Kg is [[VO2max|VO<sub>2</sub>max]] * 0.097.
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===4x4 Effort Worked Example===
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Assume your [[VO2max|VO<sub>2</sub>max]] is 53 and your weight is 60, then the initial target power is 53 * 0.097 * 60 = 309 watts. So the target range would be 260-309w at the start of the interval. Alternatively, the required pace is 0.097 * 60 = 5.14 meters/second, so the range is 4.37 to 5.14 m/s. That converts to 3:49-3:14 min/Km or 6:08-5:13 min/mile. The power or pace is then dropped to keep your heart rate below 95% max.  
 
==Wingate==
 
==Wingate==
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This style of HIIT is based around the Wingate test, which is used to measure peak anaerobic power and anaerobic capacity<ref name="Vandewalle-1987"/>. The Wingate HIIT uses 30 seconds of 'all out' intensity, followed by ~4 minutes of recovery, repeated 4-6 times.  
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This style of HIIT is based around the Wingate test, which is used to measure peak anaerobic power and anaerobic capacity<ref name="Vandewalle-1987"/>.  
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===The Wingate Test===
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The Wingate Test typically uses a warmup of 10 minutes easy cycling, followed by 2-3x 15 second sprints to get used to the speed. Then the test is normally 30 seconds all out sprinting, though some researchers use a longer period of 40-120 seconds.
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===The Test on a Smart Trainer===
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The test is performed on a mechanically braked cycle ergometer, often a Monarch model. This makes converting the settings to a smart trainer tricky. The Monarch uses a weight to provide the resistance, and the Wingate Test uses 7.5% of your body weight. The formula for working out Watts for the Monarch is the resistance in Kg multiplied by the cadence. So, if you weigh 60 Kg, 7.5% is 4.5Kg, and at a cadence of 80 rpm is 360 watts. Setting your smart trainer's resistance so you get about 360 watts at 80 rpm is a good starting point for the test.
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===The Wingate as HIIT===
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The Wingate HIIT uses 30 seconds of 'all out' intensity, followed by ~4 minutes of recovery, repeated 4-6 times. A similar warmup procedure as the test seems reasonable, with 10 minutes easy, then 2-3x 15 second sprints.  
 
==WinTab (Tabata style Wingate)==
 
==WinTab (Tabata style Wingate)==
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Most athletes that use the [[Tabata]] workout do not use the 170% [[VO2max|V?O<sub>2</sub>max]] intensity, but rather the Wingate style 'all out' intensity. Because the intensity is not fixed, the WinTab normally has 8 repetitions of 20 seconds all out plus 10 seconds rest, taking 5 minutes (plus [[Warmup]]), rather than the variable number of repetitions of the original Tabata protocol.
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Most athletes that use the [[Tabata]] workout do not use the 170% [[VO2max|V̇O<sub>2</sub>max]] intensity, but rather the Wingate style 'all out' intensity. Because the intensity is not fixed, the WinTab normally has 8 repetitions of 20 seconds all out plus 10 seconds rest, taking 4 minutes (plus [[Warmup]]), rather than the variable number of repetitions of the original [[Tabata]] protocol.
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==HillTab==
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Because the WinTab workout involves such fast paces, it can easily lead to injury as the stride length requires a greater range of motion than more common paces. You can reduce the pace while maintaining the intensity by running up hill, something I call HillTab (Hill Tabata). While similar to the WinTab in some ways, this workout has a variable length recovery, as you have to run down the hill after each time, and it uses different muscle groups. To perform a HillTab, find a hill that is moderately steep; about 10-12% gradient works well. Find a marker to use as the start point, such as a suitable tree or rock, then find an initial finish marker that is about 45 seconds up the path. You'll adjust the finish marker so that it takes about 30 seconds to cover the distance at your fastest speed. This will take a bit of trial and error, but don't worry if the first few intervals are too long or too short. You could use an audible timer, but I prefer a visible marker to aim for. If you want to time each interval, have a watch in your hand, held so you can press the lap button without fumbling. For each interval:
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# Approach the start marker at an easy pace.
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# A few yards/meters from the start, shorten your stride and increase your [[Cadence]]. Your stride will be quite short at this point.
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# As you approach the start marker, lean forward so that your weight feels over the balls of your feet and toes.
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# When you cross the start marker accelerate hard, grabbing the ground with each stride and propelling yourself forward. You'll accelerate to your maximum velocity within a handful of strides, and you'll probably be acutely aware of each footstep as the adrenaline seems to slow time. For the first few intervals this phase often has a wonderful sense of euphoria and power.
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# Try to hold on to this pace to the end marker, which may seem to grow further away. Your legs will grow weak and distant as the lack of oxygen causes your vision to fade to gray.
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# By the time your reach the end, just 30 seconds later, your lungs are starting to burn and the ecstasy you felt just moments ago has turned to desolation.
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# Slow up carefully after the end marker. Do not let your form collapse or your feet slap the ground.
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# When your pace has dropped, turn around and descend. You may find your lungs burn more after the interval than before as you start to recover.
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# Run past the start marker, turn and repeat for a total of 8 intervals.
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For HIIT, I suspect that the hard acceleration is a key to the benefits of the workout. The acceleration achieves high levels of muscle activation, mimicking the effects of Plyometrics. (There advantages to [[Downhill Running]], but the risk of injury while running at HIIT pace downhill are much higher.)
 
==Traditional Anaerobic Intervals==
 
==Traditional Anaerobic Intervals==
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High intensity Interval Training has been in use since before the [[Tabata]] study made the term popular. The Jack Daniel's 'R' paced workouts are a classic example of this tradition of anaerobic interval training. The Jack Daniel's 'R' intervals are performed at around mile/1500m pace<ref name="JD"/>, which is generally close to 100% [[VO2max|V?O<sub>2</sub>max]]. The 'R' workouts are 12-40 repeats of 30-60 seconds with 1-4 min rests<ref name="JD-P132"/>. Jack Daniels mentions once having his athletes perform over 1,000 repetitions of one minute HIIT (4 minute rest) in a 14 day period, with two male athletes averaging 5:00 min/mile pace and therefore covering 250 miles<ref name="JD-P132"/>.  
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High intensity Interval Training has been in use since before the [[Tabata]] study made the term popular. The Jack Daniel's 'R' paced workouts are a classic example of this tradition of anaerobic interval training. The Jack Daniel's 'R' intervals are performed at around mile/1500m pace<ref name="JD"/>, which is generally close to 100% [[VO2max|V̇O<sub>2</sub>max]]. The 'R' workouts are 12-40 repeats of 30-60 seconds with 1-4 min rests<ref name="JD-P132"/>. Jack Daniels mentions once having his athletes perform over 1,000 repetitions of one-minute HIIT (4-minute rest) in a 14-day period, with two male athletes averaging 5:00 min/mile pace and therefore covering 250 miles<ref name="JD-P132"/>.  
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=HIIT Training Mode=
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=Fellrnr's Tabata Audio=
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There are various ways that HIIT could be performed, each with their own pros and cons.
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I created a short audio file for my Tabata (WinTab), adding a countdown and interval counts. I started with [https://itunes.apple.com/us/album/sandstorm-ep/id251130083| Darude's Sandstorm], [[Remixing Music For Running| remixed it to 180 BPM]] and then extracted short snippets. I then recombined the snippets with voice countdowns so that I didn't need to look at a watch or timer to execute the workout. You can download or play [http://fellrnr.com/FellrnrTabata.mp3 the MP3 file of Fellrnr's Tabata]. (I believe that I'm making fair use of Darude's work, given I am only using a short section of the original and modifying it heavily. If you want to enjoy the overall song, this MP3 file is not it!)
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{| class="wikitable"
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=HIIT Training Methods=
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There are various ways that HIIT could be performed, each with their own pros and cons. As this site is dedicated to running, my assumption is that you're a runner primarily. If that's not the case, then you'll have to interpret the pros and cons slightly differently.
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{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"
 
! Mode
 
! Mode
 
! Pros
 
! Pros
 
! Cons
 
! Cons
 
|-
 
|-
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| Stationary Bike
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| [[Cycling HIIT For Runners | Stationary Bike HIIT]]
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|
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|  
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* The vast majority of studies have used a stationary bike to perform HIIT.
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* A stationary bike is much safer than writing outdoors at extreme intensities.
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* The many studies have used a stationary bike to perform HIIT.
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* Riding out of the saddle is closer to moderate running in terms of muscle usage than riding seated.
 
* A direct measure of intensity through power is often possible.  
 
* A direct measure of intensity through power is often possible.  
 
* Lowest risk of injury.  
 
* Lowest risk of injury.  
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|
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* The bike does use the same muscles as running.
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|  
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* The bike doesn't use the same [[Muscle]]s as running, nor the same range of motion.
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* There is no eccentric component to cycling.
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* The specific muscles recruited will vary depending on how much you pull up on the pedals as well is pushed down.
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|-
 
|-
−
| Bike
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| Outdoor Bike
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|
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|  
 
* Should be similar to the stationary bike, but at a lower cost.
 
* Should be similar to the stationary bike, but at a lower cost.
 
* It's easier to ride a bike out of the saddle than a stationary bike, which uses more muscles and is closer to the action of running.  
 
* It's easier to ride a bike out of the saddle than a stationary bike, which uses more muscles and is closer to the action of running.  
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|
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|  
 
* Riding a bike at high intensity adds risk due to impaired mental functioning and coordination.
 
* Riding a bike at high intensity adds risk due to impaired mental functioning and coordination.
 
* While it's possible to directly measure power output on a bike, it's expensive.
 
* While it's possible to directly measure power output on a bike, it's expensive.
 
|-
 
|-
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| Running
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| Running on the flat
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|
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|  
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* For runners, the right muscle groups are trained.
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* For runners, roughly the right muscle groups are trained.
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|
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* With [[Stryd]] it's possible to get a good measurement of pace, and even an estimate of power output. (The estimate of running power is not equivalent to cycling power, which can actually be measured rather than estimated.)
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* At high Intensity, the movements involved in running become dramatically different, requiring a greater range of motion. This difference creates a significant risk of injury. Running uphill reduces some of this stress (hill based HIIT is not uncommon<ref name="active.com-hills"/>).
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|  
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* At high Intensity, the movements involved in running become dramatically different, requiring a greater range of motion. This difference creates a significant risk of injury. It also changes the muscles used compared with running at submaximal intensity.
 
* The rapid acceleration and deceleration of HIIT creates stress that runners are not typically exposed to, again creating a risk of injury. (I suspect the risk of injury during the deceleration is often underestimated, as this is when where a runner's form often deteriorates.)
 
* The rapid acceleration and deceleration of HIIT creates stress that runners are not typically exposed to, again creating a risk of injury. (I suspect the risk of injury during the deceleration is often underestimated, as this is when where a runner's form often deteriorates.)
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* Even with a [[Footpod]] and a [[Best Running Watch| good running watch]] it's hard to measure pace accurately, and GPS is useless for the short intervals often used in HIIT. Running on a track or other known distance may be slightly easier, but it's still not trivial. (This is not a problem for 'all out' style of HIIT.)
 
 
|-
 
|-
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| Treadmill
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| Running up hill
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|
+
|
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* Running uphill generates a much higher intensity at a slower pace. This means that the biomechanical changes are not so extreme, reducing the risk of injury.
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|
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* Running uphill uses somewhat different muscles to running on the flat, so the training stress is not identical.
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* It's hard to find a hill that's long enough to do a high intensity interval training session that includes only partial recovery.
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* Getting the right incline is a tricky balance. Too shallow, and you may as well be running on the flat. Too steep and your biomechanics become exaggeratedly different.
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|-
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| Running with extra drag
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|
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* It's possible to use a [[Running Parachute]], or drag a tire behind you to increase intensity at a slower pace.
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* The slower pace means a less extreme stride length and biomechanical changes, reducing risk of injury from those changes.
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|
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* The additional track creates radically different muscle recruitment patterns.
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* For a full list of downsides see [[Running Parachute]]s.
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|-
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| [[Treadmill]]
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|  
 
* It's possible to run in weather that is too hostile for outside activities.  
 
* It's possible to run in weather that is too hostile for outside activities.  
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|
+
|  
 
* Most treadmills will not change pace fast enough for the dramatic changes in pace between interval and recovery used in HIIT.
 
* Most treadmills will not change pace fast enough for the dramatic changes in pace between interval and recovery used in HIIT.
 
* Matching acceleration and deceleration with the treadmill is not easy, especially when mental functioning is impaired, as it so often is at high intensity
 
* Matching acceleration and deceleration with the treadmill is not easy, especially when mental functioning is impaired, as it so often is at high intensity
Line 64: Line 136:
 
|}
 
|}
 
=HIIT Running Paces=
 
=HIIT Running Paces=
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I don't generally recommend running HIIT workouts because of the high speeds required. Below is a sampling of the HIIT paces for different fitness levels ([[VO2max|V?O<sub>2</sub>max]]). For each level, the 5K and marathon times are given, along with the pace that corresponds to 90%, 100% and 170% of [[VO2max|V?O<sub>2</sub>max]].  
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I don't generally recommend running HIIT workouts because of the high speeds required. Below is a sampling of the HIIT paces for different fitness levels ([[VO2max|V̇O<sub>2</sub>max]]). For each level, the 5K and marathon times are given, along with the pace that corresponds to 90%, 100% and 170% of [[VO2max|V̇O<sub>2</sub>max]].  
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{| class="wikitable"
+
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"
−
! [[VO2max|V?O<sub>2</sub>max]]
+
! [[VO2max|V̇O<sub>2</sub>max]]
 
! 35
 
! 35
 
! 40
 
! 40
Line 105: Line 177:
 
| 2:00:58
 
| 2:00:58
 
|-
 
|-
−
| 90% V?O2max
+
| 90% [[VO2max|V̇O<sub>2</sub>max]]
 
| 9:09/Mile
 
| 9:09/Mile
 
| 8:13/Mile
 
| 8:13/Mile
Line 118: Line 190:
 
| 4:27/Mile
 
| 4:27/Mile
 
|-
 
|-
−
| 100% V?O2max
+
| 100% [[VO2max|V̇O<sub>2</sub>max]]
 
| 8:24/Mile
 
| 8:24/Mile
 
| 7:33/Mile
 
| 7:33/Mile
Line 131: Line 203:
 
| 4:06/Mile
 
| 4:06/Mile
 
|-
 
|-
−
| 170% V?O2max
+
| 170% [[VO2max|V̇O<sub>2</sub>max]]
 
| 5:28/Mile
 
| 5:28/Mile
 
| 4:54/Mile
 
| 4:54/Mile
Line 144: Line 216:
 
| 2:41/Mile
 
| 2:41/Mile
 
|}
 
|}
 +
=HIIT and Stryd=
 +
The [[Stryd]] footpod gives an extremely accurate measure of pace and incline, and from this it calculates an estimate of your power output in Watts. This power estimate responds much faster than Heart Rate, which is pretty useless for evaluating a HIIT session.
 +
[[File:PowerHeartRate.jpg|center|thumb|300px|A graph of Heart Rate against [[Stryd]] power estimate for a HIIT session.]]
 
=The HIIT Science=
 
=The HIIT Science=
−
This section looks at the scientific evidence, divided into three sections. Studies that compare HIIT with other modes of training are the most interesting, though they don't cover highly trained athletes. I've included a few other studies that are not comparative because they have some particularly dramatic results. The third section looks at the studies that have looked at HIIT for highly trained athletes.
+
For details of the science around HIIT, see [[The Science of High Intensity Interval Training]].
−
==HIIT Comparisons on Untrained or Moderately Active Subjects==
 
−
The table below looks at studies that have compared HIIT with other types of training, often Continuous Moderate Exercise (CME). These studies on untrained or moderately trained subjects generally show a greater improvement in fitness measure compared with other forms of training, or similar improvements for far less training time.
 
−
{| class="wikitable"
 
−
! Study
 
−
! Subjects
 
−
! Study length
 
−
! Protocol
 
−
! Outcome
 
−
! Best Result
 
−
! Notes
 
−
|-
 
−
| rowspan="4"|
 
−
Helgerud-2007<ref name="Helgerud-2007"/>
 
−
| rowspan="4"|
 
−
Moderately trained
 
−
([[VO2max|V?O<sub>2</sub>max]] 51-55)
 
−
| rowspan="4"|
 
−
3 days/week
 
−
8 weeks
 
−
| '''Short HIIT'''
 
−
47x 15 seconds at 90-95% [[Maximum Heart Rate|HR<sub>max</sub>]] + 15 seconds at 70% [[Maximum Heart Rate|HR<sub>max</sub>]]
 
−
| Raised [[VO2max|V?O<sub>2</sub>max]] 7.2%
 
−
| rowspan="4"|
 
−
Short HIIT
 
−
| rowspan="4"|
 
−
All groups improved economy, with no differences, and Lactate Threshold unchanged as a percentage of [[VO2max|V?O<sub>2</sub>max]]
 
−
|-
 
−
| '''Long HIIT'''
 
−
4x 4 min, 90-95% [[Maximum Heart Rate|HR<sub>max</sub>]] + 3 min at 70%max
 
−
| Raised [[VO2max|V?O<sub>2</sub>max]] 5.5%
 
−
|-
 
−
| '''Lactate threshold run'''
 
−
24 min at 85% [[Maximum Heart Rate|HR<sub>max</sub>]]
 
−
| [[VO2max|V?O<sub>2</sub>max]] unchanged
 
−
|-
 
−
| '''Long Slow Distance'''
 
−
45 minutes at 70% [[Maximum Heart Rate|HR<sub>max</sub>]]
 
−
| [[VO2max|V?O<sub>2</sub>max]] unchanged
 
−
|-
 
−
| rowspan="2"|
 
−
TjonnaLee-2008<ref name="TjonnaLee2008"/>
 
−
| rowspan="2"|
 
−
Untrained, metabolic syndrome patients
 
−
| rowspan="2"|
 
−
3 days/week
 
−
16 weeks
 
−
| '''HIIT'''
 
−
4x 4 min at 90% [[Maximum Heart Rate|HR<sub>max</sub>]] + 3 min 70% [[Maximum Heart Rate|HR<sub>max</sub>]]
 
−
total 40 min,
 
−
| Raised [[VO2max|V?O<sub>2</sub>max]] 36%
 
−
| rowspan="2"|
 
−
HIIT
 
−
| rowspan="2"|
 
−
Same calories burned in each group
 
−
Both groups had an equal reduction in body weight and blood pressure
 
−
|-
 
−
| '''Continuous Moderate Exercise'''
 
−
47 min at 70% [[Maximum Heart Rate|HR<sub>max</sub>]]
 
−
| Raised [[VO2max|V?O<sub>2</sub>max]] 16%
 
−
|-
 
−
| rowspan="2"|
 
−
Gibala-2006<ref name="Gibala-2006"/>
 
−
| rowspan="2"|
 
−
Recreationally active
 
−
| rowspan="2"|
 
−
2 weeks
 
−
| '''HIIT'''
 
−
4-6x 30 seconds 'all out' + 4 min recovery
 
−
Totals for two weeks, 135 minutes and 950 Kj
 
−
| rowspan="2"|
 
−
Same improvement in laboratory time trials
 
−
| rowspan="2"|
 
−
HIIT
 
−
| rowspan="2"|
 
−
Same improvement, but only 22% of the time commitment
 
−
|-
 
−
| '''Continuous Moderate Exercise'''
 
−
90-120 min at 65% [[VO2max|V?O<sub>2</sub>peak]]
 
−
Totals for two weeks, 630 minutes and 6500 Kj
 
−
|-
 
−
| rowspan="2"|
 
−
Gorostiaga-1991<ref name="Gorostiaga-1991"/>
 
−
| rowspan="2"|
 
−
Sedentary
 
−
| rowspan="2"|
 
−
3 days/week
 
−
8 weeks
 
−
| '''HIIT'''
 
−
30x 30 sec @ 100% [[VO2max|V?O<sub>2</sub>max]] + 30 sec rest
 
−
| Raised [[VO2max|V?O<sub>2</sub>max]] 9-16%
 
−
No change in blood lactate during continuous exercise
 
−
| rowspan="2"|
 
−
HIIT
 
−
| rowspan="2"|
 
−
Same average work in each group
 
−
|-
 
−
| '''Continuous Moderate Exercise'''
 
−
30 minutes at 50% [[VO2max|V?O<sub>2</sub>max]]
 
−
| Raised [[VO2max|V?O<sub>2</sub>max]] 5-7%
 
−
Reduced blood lactate during continuous exercise by nearly 50%
 
−
|-
 
−
| rowspan="3"|
 
−
Franch-1998<ref name="Franch-1998"/>
 
−
| rowspan="3"|
 
−
36 recreational runners
 
−
| rowspan="3"|
 
−
3 days/week at high intensity
 
−
Plus 3 runs/week <= 65% [[Maximum Heart Rate|HR<sub>max</sub>]]
 
−
6 weeks
 
−
| '''Short HIIT'''
 
−
30-40x 15 sec run, 15 sec rest
 
−
Avg ~3.0 Km/workout
 
−
92% [[Maximum Heart Rate|HR<sub>max</sub>]]
 
−
| Time to exhaustion increased 65%
 
−
Running economy improved 0.9%
 
−
| rowspan="3"|
 
−
Continuous High Intensity
 
−
| rowspan="3"|
 
−
Better improvements from continuous training than HIIT, but the continuous training is at an unusually high intensity that is probably close to a 10K race, three times a week.
 
−
|-
 
−
| '''Long HIIT'''
 
−
4-6x 4 min run, 2 min rest
 
−
Avg ~5.6 Km/workout
 
−
94% [[Maximum Heart Rate|HR<sub>max</sub>]]
 
−
| Time to exhaustion increased 67%
 
−
Running economy improved 3.0%
 
−
|-
 
−
| '''Continuous High Intensity'''
 
−
20-30 minutes
 
−
Avg ~6.4 Km/workout
 
−
93% [[Maximum Heart Rate|HR<sub>max</sub>]]
 
−
| Time to exhaustion increased 94%
 
−
Running economy improved 3.1%
 
−
|-
 
−
| rowspan="2"|
 
−
BurgomasterHowarth-2007<ref name="BurgomasterHowarth2007"/>
 
−
| rowspan="2"|
 
−
20 Untrained
 
−
| rowspan="2"|
 
−
HIIT 3x week
 
−
Continuous 5x week
 
−
6 weeks
 
−
| '''HIIT'''
 
−
4-6x 30 seconds 'all out', 4.5 min rest
 
−
1.5 hours/week
 
−
~225 Kj/week
 
−
| rowspan="2"|
 
−
Both increased [[VO2max|V?O<sub>2</sub>peak]] by ~5%
 
−
| rowspan="2"|
 
−
HIIT
 
−
| rowspan="2"|
 
−
Similar changes in HIIT for 10% of the workload and 30% of the time of continuous training.
 
−
|-
 
−
| '''Continuous Moderate Exercise'''
 
−
40-60 min at 65% [[VO2max|V?O<sub>2</sub>peak]]
 
−
4.5 hours/week
 
−
2250 Kj/week
 
−
|-
 
−
| rowspan="2"|
 
−
Trapp-2008<ref name="Trapp-2008"/>
 
−
| rowspan="2"|
 
−
34 sedentary women
 
−
| rowspan="2"|
 
−
45 workouts over 15 weeks
 
−
| '''HIIT'''
 
−
60x 8 seconds 'all out', 12 seconds rest (5 min [[Warmup]], 20 min conditioning, 5 min cooldown)
 
−
| Increased [[VO2max|V?O<sub>2</sub>peak]] 24%
 
−
5 pound/2.5 Kg reduction in body fat
 
−
Significant 31% reduction in fasting insulin
 
−
Significant reduction in [http://en.wikipedia.org/wiki/Leptin Leptin]
 
−
| rowspan="2"|
 
−
HIIT
 
−
| rowspan="2"|
 
−
HIIT produced similar improvements in fitness for a lower time commitment, as well as a reduction in body fat that was not seen with continuous exercise.
 
−
|-
 
−
| '''Continuous Moderate Exercise'''
 
−
40 minutes at 60% [[VO2max|V?O<sub>2</sub>peak]]
 
−
| Increased [[VO2max|V?O<sub>2</sub>peak]] 19%
 
−
1 pound/0.5 Kg gain in body fat
 
−
Non-significant 9% reduction in fasting insulin
 
−
No change in [http://en.wikipedia.org/wiki/Leptin Leptin]
 
−
|-
 
−
| rowspan="2"|
 
−
Tabata-1996<ref name="Tabata-1996"/>
 
−
| rowspan="2"|
 
−
14 varsity level collage athletes ([[VO2max|V?O<sub>2</sub>max]] ~50)
 
−
| rowspan="2"|
 
−
5 days/week
 
−
6 weeks
 
−
| '''HIIT'''
 
−
4 days/week 7-8x (30 seconds at 170% [[VO2max|V?O<sub>2</sub>max]] + 10 seconds rest)
 
−
1 day/week 30 min at 70% [[VO2max|V?O<sub>2</sub>max]] + 4x (30 seconds at 170% [[VO2max|V?O<sub>2</sub>max]] + 10 seconds rest)
 
−
| Raised [[VO2max|V?O<sub>2</sub>max]] by 14.5%
 
−
Increased anaerobic capacity by 28%
 
−
| rowspan="2"|
 
−
HIIT
 
−
| rowspan="2"|
 
−
HIIT produced a greater improvement in [[VO2max|V?O<sub>2</sub>max]] for far less time commitment
 
−
|-
 
−
| '''Continuous Moderate Exercise'''
 
−
60 minutes at 70% [[VO2max|V?O<sub>2</sub>max]]
 
−
| Raised [[VO2max|V?O<sub>2</sub>max]] by 9.5%
 
−
No change in anaerobic capacity
 
−
|}
 
−
==HIIT Studies on Untrained or Moderately Active Subjects==
 
−
While studies that compare HIIT with other forms of training are the most useful, there are a few other studies on untrained or moderately active people that are noteworthy. For instance, six sessions of HIIT over two weeks doubled the endurance of untrained subjects at 80% [[VO2max|V?O<sub>2</sub>max]] from 25 to 51 minutes, despite no change in [[VO2max|V?O<sub>2</sub>max]]<ref name="Burgomaster-2005"/>, a remarkable improvement. In another study, the combination of Continuous Moderate Exercise and moderate intensity intervals (60-70% [[VO2max|V?O<sub>2</sub>max]]) reduced body fat by 15%, which was nine times more than Continuous Moderate Exercise alone, even though the Continuous Moderate Exercise burned over twice the calories<ref name="Tremblay-1994"/>. Another study also used a combination of HIIT on 3 day/week plus running as far as possible in 40 min on another 3 days/week , resulting in an increase in [[VO2max|V?O<sub>2</sub>max]] by 44%, as well as improved running endurance, with some subjects ending up with a [[VO2max|V?O<sub>2</sub>max]] exceeding 60 ml/kg per min, which is remarkably high for 10 weeks of training<ref name="Hickson-1977"/>.
 
−
==HIIT and Highly Trained Athletes==
 
−
It has been suggested that elite athletes do not benefit from further increases in volume, and should instead look to HIIT for performance improvements<ref name="Laursen-1-2002"/>. This is backed up by studies of some of the great endurance athletes, where higher training mileage produced worse rather than better performance<ref name="elitemileage"/>. In the Lore of Running, Tim Noakes said that elite runners perform best "when they train between 75-125 miles (120-200 km) per week, with an increasing likelihood that they will perform indifferently when they train more than 125 miles (200 km) per week"<ref name="LoR-P477"/>. Of course this is not universally true, and Mike Morton, set the US record holder for 24 hour while training 140-150 miles/week<ref name="militarytimes.com"/>. However, the evaluation of HIIT on elite athletes is not as easy as lessor folk. It's not practical to compare the effect of HIIT with other forms of exercise in highly trained athletes as they are typically already performing large volumes of Continuous Moderate Exercise. Instead, studies of highly trained athletes look at how HIIT impacts their fitness compared with a baseline taken beforehand.
 
−
* HIIT improved peak power output and 40 Km time trial in elite cyclists<ref name="Lindsay-1996"/><ref name="Westgarth-Taylor-1997"/>
 
−
* A study of elite cyclists used various HIIT workouts as shown in the table below, with the best results seen group 4 or group 1<ref name="Stepto-1999"/>. Group 4 trained at 85% peak power, which corresponds to the intensity normally seen in the 40K time trial, which takes ~60 minutes for an elite cyclist. Not surprisingly, this intensity is commonly used for cyclists training for 40K time trials. However, the higher intensity of group 1 is more intriguing; the time trial performance improved without an improvement in peak power, suggesting that a different mechanism may be responsible. This raises the possibility that the benefits of the different intensities might be combined. Note that there were only four athletes in each group, and responses tended to vary, so caution should be used in interpreting the results.
 
−
{| class="wikitable"
 
−
! Group
 
−
! Number of intervals
 
−
! Interval duration (min)
 
−
! Total work time (min)
 
−
! Intensity (% peak power)
 
−
! Rest (min)
 
−
! Total Time
 
−
! Improvement in 40K Time Trial Speed
 
−
! Improvement in Peak Power
 
−
|-
 
−
| 1
 
−
| 12
 
−
| 0.5
 
−
| 6
 
−
| 175%
 
−
| 4.5
 
−
| 60 min
 
−
| 2.0%
 
−
| 0.5%
 
−
|-
 
−
| 2
 
−
| 12
 
−
| 1
 
−
| 12
 
−
| 100%
 
−
| 4.0
 
−
| 60 min
 
−
| 0.0%
 
−
| 0.5%
 
−
|-
 
−
| 3
 
−
| 12
 
−
| 2
 
−
| 24
 
−
| 90%
 
−
| 3.0
 
−
| 60 min
 
−
| 1.5%
 
−
| 1.5%
 
−
|-
 
−
| 4
 
−
| 8
 
−
| 4
 
−
| 32
 
−
| 85%
 
−
| 1.5
 
−
| 44 min
 
−
| 2.5%
 
−
| 2.0%
 
−
|-
 
−
| 5
 
−
| 4
 
−
| 8
 
−
| 32
 
−
| 80%
 
−
| 1.0
 
−
| 36 min
 
−
| 0.0%
 
−
| 1.0%
 
−
|}
 
−
* One approach to optimizing the length of the intervals in highly trained athletes is to use a percentage of [[vVO2max|T<sub>lim</sub>]] , where [[vVO2max|T<sub>lim</sub>]] is the time to exhaustion at 100% [[VO2max|V?O<sub>2</sub>max]]<ref name="Laursen-1-2002"/>.
 
−
* 5 state level middle distance runners that underwent 4 weeks of HIIT training reduced their 3K time by 2.8% (10:16 to 9:59) and [[VO2max|V?O<sub>2</sub>max]] by 4.9% (61 to 64)<ref name="Smith-1999"/>. The HIIT training consisted of 2 sessions per week of 6 intervals at 100% [[VO2max|V?O<sub>2</sub>max]] with time varying between 60-75% [[vVO2max|T<sub>lim</sub>]], plus one weekly run of 30 min at 60% v[[VO2max|V?O<sub>2</sub>max]]. For these runners, [[vVO2max|T<sub>lim</sub>]] averaged 225 seconds, so the intervals were between 135 and 170 seconds.
 
−
* Well trained, competitive runners trained twice a week for four weeks with intervals at 100% [[VO2max|V?O<sub>2</sub>max]] for either 6x 60% [[vVO2max|T<sub>lim</sub>]] (133 sec) or 5x 70% (154 sec) [[vVO2max|T<sub>lim</sub>]], resting for twice the interval time. Their 3K time improved by 17.6 sec (60% [[vVO2max|T<sub>lim</sub>]]) or 6.3 sec (70% [[vVO2max|T<sub>lim</sub>]]), but there was no change in their 5K time<ref name="Smith-2003"/>.
 
−
* 41 elite ([[VO2max|V?O<sub>2</sub>peak]] ~65) cyclists and triathletes were split into four groups, with three groups using the HIIT described below and the fourth acting as a control that followed only low to moderate intensity training<ref name="Laursen-3-2002"/>. Note that groups 1 and 2 vary only in their rest time, which is based on heart rate dropping to 65% of [[Maximum Heart Rate|HR<sub>max</sub>]] in group 2 (averaging around 180 seconds). This was a demanding regime, as the subjects reached exhaustion on nearly every HIIT training session, with '''only 64% of the dictated intervals actually completed'''. Note that like comparison of different workouts above, the shorter HIIT produced a similar improvement in 40K performance without the accompanying rise in [[VO2max|V?O<sub>2</sub>max]] which was not statistically different between group 3 and the controls.
 
−
{| class="wikitable"
 
−
! Group
 
−
! Intended number of intervals
 
−
! Interval Duration
 
−
! Total work time (min)
 
−
! Intensity (% [[VO2max|V?O<sub>2</sub>max]])
 
−
! Rest
 
−
! Total time
 
−
! [[VO2max|V?O<sub>2</sub>max]] change
 
−
! 40K Time Trial Speed improvement
 
−
|-
 
−
| 1
 
−
| 8
 
−
| 60% [[vVO2max|T<sub>lim</sub>]]<sub></sub>(~150 sec)
 
−
| 20
 
−
| 100%
 
−
| 120% [[vVO2max|T<sub>lim</sub>]] (~290 sec)
 
−
| 58 min
 
−
| 5.2%
 
−
| 5.2%
 
−
|-
 
−
| 2
 
−
| 8
 
−
| 60% [[vVO2max|T<sub>lim</sub>]]<sub></sub>(~150 sec)
 
−
| 20
 
−
| 100%
 
−
| 65% [[Maximum Heart Rate|HR<sub>max</sub>]] (~180 sec)
 
−
| Varies
 
−
| 8.0%
 
−
| 5.6%
 
−
|-
 
−
| 3
 
−
| 12
 
−
| 30 seconds
 
−
| 6
 
−
| 175%
 
−
| 4.5 min
 
−
| 60 min
 
−
| 3.1%
 
−
| 4.3%
 
−
|-
 
−
| Control
 
−
| N/A
 
−
| N/A
 
−
| N/A
 
−
| N/A
 
−
| N/A
 
−
| N/A
 
−
| 0.8%
 
−
| -1%
 
−
|}
 
−
* Elite cyclists performed  4 sessions of HIIT (20x 60 sec at [[VO2max|V?O<sub>2</sub>max]] + 120 sec recovery) that improved peak power by 4% but had no change in [[VO2max|V?O<sub>2</sub>max]]<ref name="Laursen-2-2002"/>.
 
−
==Limitations of the HIIT science==
 
−
There are some important limitations of the HIIT science.
 
−
* The majority of studies are on sedentary or recreationally active people, not trained runners.
 
−
* Few studies use real world measures of improvement, relying instead on indirect metrics such as [[VO2max|V?O<sub>2</sub>max]]. While [[VO2max|V?O<sub>2</sub>max]] is linked to improved performance, there are other important factors involved.
 
−
* Studies that do look at the effect of HIIT on real world performance tend to focus on shorter events, such as 3K or 5K running, or 40K cycling.
 
−
* Most studies are short duration, looking at the effects of HIIT over just a few weeks.
 
 
=Crossfit Endurance=
 
=Crossfit Endurance=
−
Crossfit Endurance is a training approach that reduces the normal endurance training volumes while increasing the training intensity<ref name="www.crossfitendurance.com-about"/>.  The reduction in volume is quite dramatic compared with other training plans; for instance, the Crossfit Endurance marathon training plan has a 10 mile time trial as its longest run, which is combined with weight training and interval training<ref name="crossfitmarathon"/>. While there are some testimonials to the Crossfit Endurance methodology<ref name="www.crossfitendurance.com-test"/>, their approach is controversial<ref name="SoRCf"/>. The science that is used to support Crossfit Endurance does not support replacing traditional Continuous Moderate Exercise with HIIT for endurance events, only using HIIT as a supplementary form of training<ref name="metamorphitness.wordpress.com"/>. Most of the anecdotal reports suggest that people have set personal records at 5K and 10K distances and completed half marathons using the Crossfit Endurance approach, but there are few reports of longer races. The anecdotal reports are hard to interpret objectively without knowing the individuals prior training methodology.  
+
Crossfit Endurance is a training approach that reduces the normal endurance training volumes while increasing the training intensity<ref name="www.crossfitendurance.com-about"/>.  The reduction in volume is quite dramatic compared with other training plans; for instance, the Crossfit Endurance marathon training plan has a 10 mile time trial as its longest run, which is combined with weight training and interval training<ref name="crossfitmarathon"/>. Crossfit Endurance claims that eight 100 meter intervals "accomplishes everything you would by jogging 20 miles but doesn't put the same level of stress and damage on the body." There is the caveat that "some kind of stamina work that lost more than the 70 seconds is required to "dial in technique, just rhythm, and formulate pace strategy." While there are some testimonials to the Crossfit Endurance methodology<ref name="www.crossfitendurance.com-test"/>, their approach is controversial<ref name="SoRCf"/>. The science that is used to support Crossfit Endurance does not support replacing traditional Continuous Moderate Exercise with HIIT for endurance events, only using HIIT as a supplementary form of training<ref name="metamorphitness.wordpress.com"/>. Most of the anecdotal reports suggest that people have set personal records at 5K and 10K distances and completed half marathons using the Crossfit Endurance approach, but there are few reports of longer races. The anecdotal reports are hard to interpret objectively without knowing the individuals prior training methodology. (I have some other concerns with CrossFit, such as their emphasis on forefoot landing, then approach to hydration that includes the overly simplistic "sweat rate test", but that's outside of the scope of this article that focuses on interval training.)
 
=References=
 
=References=
 
<references>
 
<references>
Line 488: Line 230:
 
<ref name="www.crossfitendurance.com-about"> About Crossfit Endurance, http://www.crossfitendurance.com/whatiscfe, Accessed on 26 February 2013</ref>
 
<ref name="www.crossfitendurance.com-about"> About Crossfit Endurance, http://www.crossfitendurance.com/whatiscfe, Accessed on 26 February 2013</ref>
 
<ref name="crossfitmarathon"> http://www.outsideonline.com/fitness/endurance-training/CrossFit-Endurances-Unconventional-12-Week-Marathon-Training-Plan.html, http://www.outsideonline.com/fitness/endurance-training/CrossFit-Endurances-Unconventional-12-Week-Marathon-Training-Plan.html, Accessed on 26 February 2013</ref>
 
<ref name="crossfitmarathon"> http://www.outsideonline.com/fitness/endurance-training/CrossFit-Endurances-Unconventional-12-Week-Marathon-Training-Plan.html, http://www.outsideonline.com/fitness/endurance-training/CrossFit-Endurances-Unconventional-12-Week-Marathon-Training-Plan.html, Accessed on 26 February 2013</ref>
−
<ref name="Tabata-1996">I. Tabata, K. Nishimura, M. Kouzaki, Y. Hirai, F. Ogita, M. Miyachi, K. Yamamoto, Effects of moderate-intensity endurance and high-intensity intermittent training on anaerobic capacity and [[VO2max, Med Sci Sports Exerc, volume 28, issue 10, pages 1327-30, Oct 1996, PMID [http://www.ncbi.nlm.nih.gov/pubmed/8897392 8897392]</ref>
 
−
<ref name="Smith-2003"> TP. Smith, JS. Coombes, DP. Geraghty, Optimising high-intensity treadmill training using the running speed at maximal O(2) uptake and the time for which this can be maintained., Eur J Appl Physiol, volume 89, issue 3-4, pages 337-43, May 2003, doi [http://dx.doi.org/10.1007/s00421-003-0806-6 10.1007/s00421-003-0806-6], PMID [http://www.ncbi.nlm.nih.gov/pubmed/12736843 12736843]</ref>
 
−
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<ref name="Boutcher2011">Stephen H. Boutcher, High-Intensity Intermittent Exercise and Fat Loss, Journal of Obesity, volume 2011, 2011, pages 1–10, ISSN [http://www.worldcat.org/issn/2090-0708 2090-0708], doi [http://dx.doi.org/10.1155/2011/868305 10.1155/2011/868305]</ref>
 
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<ref name="Gibala-2006"> MJ. Gibala, JP. Little, M. van Essen, GP. Wilkin, KA. Burgomaster, A. Safdar, S. Raha, MA. Tarnopolsky, Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance., J Physiol, volume 575, issue Pt 3, pages 901-11, Sep 2006, doi [http://dx.doi.org/10.1113/jphysiol.2006.112094 10.1113/jphysiol.2006.112094], PMID [http://www.ncbi.nlm.nih.gov/pubmed/16825308 16825308]</ref>
 
<ref name="Gibala-2006"> MJ. Gibala, JP. Little, M. van Essen, GP. Wilkin, KA. Burgomaster, A. Safdar, S. Raha, MA. Tarnopolsky, Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance., J Physiol, volume 575, issue Pt 3, pages 901-11, Sep 2006, doi [http://dx.doi.org/10.1113/jphysiol.2006.112094 10.1113/jphysiol.2006.112094], PMID [http://www.ncbi.nlm.nih.gov/pubmed/16825308 16825308]</ref>
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<ref name="elitemileage"> An Interesting Analysis of Some Elites&#8217; Training History, Accessed on 26 February 2013</ref>
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<ref name="militarytimes.com"> http://militarytimes.com/blogs/pt365/2012/05/07/army-master-sgt-mike-morton-and-his-14-year-journey-to-the-badwater-135-ultramarathon/, http://militarytimes.com/blogs/pt365/2012/05/07/army-master-sgt-mike-morton-and-his-14-year-journey-to-the-badwater-135-ultramarathon/, Accessed on 26 February 2013</ref>
 
 
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Latest revision as of 02:41, 21 August 2023

To run HIIT intervals requires a longer stride length, so other modes, such as a stationary bike may be more appropriate.

HIIT can be highly effective training, but involves a risk of injury. HIIT has been shown to improve aerobic capacity in untrained and moderately active individuals more quickly than Continuous Moderate Exercise, as well as having potential benefits for highly trained athletes. HIIT has also been shown to reduce body fat in untrained people more effectively than Continuous Moderate Exercise. However, there is no evidence to suggest that HIIT can replace other forms of training for endurance races. High Intensity Interval Training (HIIT) uses repeated short periods of very intense cardiovascular exercise separated by lower intensity recoveries. (I've found the Stryd estimate of power output is the best approach to gauging effort during HIIT, though Moxy can provide some interesting insight from Muscle Oxygen Saturation.) If you'd like to know more about the science behind HIIT, see The Science of High Intensity Interval Training.

1 What is HIIT?

High Intensity Interval Training is a form of Interval Training using short intervals of 10 seconds to 5 minutes at an intensity at or above 90% V̇O2max[1]. High Intensity Interval Training, abbreviated to HIIT or HIT, is sometimes called High-Intensity Intermittent Exercise[2] or Sprint Training[3].

2 HIIT Recommendations

Below are my recommendations based on my interpretation of the available evidence. These recommendations for incorporating HIIT in your training depend on your current fitness goals.

  • To reduce injury risk, I strongly recommend performing HIIT on a stationary bike trainer rather than running. See "HIIT Training Methods" below for details.
  • Ease into HIIT gently, following Safe Speedwork recommendations.
  • For sedentary people, HIIT is probably more effective in building initial fitness than Continuous Moderate Exercise. Three sessions per week of Wingate HIIT on a stationary bike should provide an improvement in fitness for a modest time commitment. Using WinTab style HIIT may produce similar benefits for a lower time commitment.
  • For people looking to lose weight, HIIT will probably produce a greater reduction in body fat than Continuous Moderate Exercise. Three sessions per week of Wingate HIIT on a stationary bike should help with Weight Loss and appetite control. The HIIT could be combined with other forms of exercise on the other days, which may further improve weight loss. (HIIT probably more effective than Continuous Moderate Exercise at improving insulin sensitivity.)
  • Recreationally active people looking for rounded fitness may benefit from including HIIT in their overall training program. Adding 1-3 sessions per week of Wingate or WinTab HIIT on a stationary bike should provide an improvement in fitness.
  • Athletes focused on improving their performance in endurance races lasting less than an hour will probably benefit from replacing some of their training load with a combination of both traditional HIIT and shorter Wingate or WinTab style HIIT. Up to one traditional HIIT or 1-3 shorter HIIT sessions could be included in a weekly training routine. Care should be taken to increase Training Load slowly with the additional HIIT and try to avoid increasing Training Monotony. The traditional HIIT should be performed by running on a track or other outdoor location. For the shorter HIIT, a stationary bike probably has a lower injury risk, but the additional benefits of outdoor running may outweigh the additional injury risk. However, the fast paces of the shorter HIIT should be introduced gradually, building up the pace over a number of workouts. See Cycling HIIT For Runners for details.
  • There is no direct evidence to indicate if HIIT will help athletes focused on improving their performance in events lasting longer than an hour. However, it seems reasonable that HIIT would provide some benefits. Including 1 or 2 Wingate or WinTab HIIT sessions per week may be appropriate. Using HIIT followed immediately by endurance training may mimic some of the effects of longer training. As noted in the prior bullet point for shorter duration athletes, care should be taken to monitor Training Load and Training Monotony. As with athletes focusing on events lasting less than an hour, the stationary bike has the lowest injury risk, but there may be benefits to other training modes. However, athletes competing in longer duration events typically don't have the same need for the very high paces that are sometimes seen at the end of shorter events.
  • There is no evidence to suggest that HIIT can be used to replace Continuous Moderate Exercise such as the Long Run that is a core part of endurance training.
  • HIIT can rapidly deplete Glycogen stores, creating the possibility of using HIIT followed by lower intensity endurance training to mimic the effects of a much longer training session.
  • While Glycogen stores are restored fairly quickly afterward, it seems like much of that may come from breaking down muscle protein. For the research behind this, see Glycogen Depletion and HIIT. Taking in calories in the form of carbohydrate and protein very soon after HIIT will help prevent muscle loss.
  • For "all out" intensities, fewer intervals may be more effective. In my experience, 2 intervals, win the second at a slightly lower resistance (slope on the bike) is optimum for reaching and maintaining the highest workloads.

3 Incorporating HIIT In Your Training Regime

Here are some suggestions for adding HIIT to your training. These are not hard and fast rules, as there is a lot of individual variability.

  • HIIT sessions should be considered hard workouts, so don't try to replace easy or rest days with HIIT while leaving your hard training as is.
  • If your existing training is not already structured around hard days interspersed with rest days, then HIIT should be distributed through the week and you should take it easier on other days.
  • If you are already structuring your workouts around hard days, you should replace a hard workout with HIIT rather than adding to your workload. (Monitoring your Training Monotony may help prevent Overtraining.)
  • If you're looking to increase your training load, then HIIT may be an option. I would recommend starting off by replacing a hard workout with HIIT, then adding the original workload back over time. Remember that it can take several weeks for the additional fatigue to manifest itself, as fatigue builds up over a remarkably long time.
  • One approach to using HIIT to increase your workload would be to incorporate a HIIT workout with a moderate length long run. There's not much evidence to know the optimum approach, or how this might change the effectiveness of HIIT. It seems likely that the HIIT would create additional fatigue and Glycogen Depletion, which would make the run seem much longer than the distance would suggest. For instance, a 16 mile moderately long run could be replaced by a HIIT and 10 miles. The exact details are going to be quite individual, so experiment based on feeling.
  • Another way of increasing your training load via HIIT would be to use the HIIT workout as a second workout on a hard day. This may be of particular value if you're only running 3-4 days per week (as I recommend.)

4 Types of HIIT

There are various different protocols for performing HIIT. While the Tabata is probably the most widely recognized name in HIIT, it is one of the least studied and the least used.

4.1 Tabata

Main article: Tabata

The Tabata workout is one of the best-known protocols for HIIT and consists of 7-8 repeats of 20 seconds at 170% of V̇O2max with 10 seconds rest. The number of repetitions is defined by how long the required intensity can be maintained. An athlete should be able to complete 7-8 intervals; if 9 can be performed, the intensity is increased. However, few people actually follow the Tabata protocol because it requires specialist equipment to measure V̇O2max, then calculate 1.7x the V̇O2max workload that should be used. In practice, most people do what I call the WinTab workout (see below).

4.2 4 x 4 (The Norwegian Method)

Main article: Medium Intensity High Volume Intervals


The original Norwegian Method is to perform four intervals, each of four minutes at 90-95% of maximum heart rate, with 3-minute recoveries, often called "4x4". At first glance this appears to be an odd specification, as it's impossible to immediately increase your heart rate to 90% of maximum, and the original definition[4] talks about trying to get your heart rate to 90% or above in 60-90 seconds, then adjust the effort to keep your heart rate in range. This approach was refined by a more detailed study[5] that used a range of 85-95% of max heart rate. In that study, the subjects increased their effort rapidly to 85-100% of the effort for their VO2max. After their heart rate reached 95% of max, the effort was reduced to keep it in the 85-95% range. What's that mean in practice? Given the details below, you need to estimate your VO2max, then either work out your pace or power.

  • Power. Use the formula "weight in Kg * VO2max * 0.097". You then start the 4-minute interval at 85-100% of that power.
  • Pace. Luckily, it happens that pace in meters/second is roughly the same as power in watts/Kg. So you can use the formula to "VO2max * 0.097" to estimate your target pace in meters/second, then use an online converter to change that to min/mile or min/Km.

Dropping your effort as the interval progresses may result in a surprisingly large reduction, with the study showing that that most intervals ended at about 60% of the initial power. The study also showed that the second through fourth interval had a lower initial power requirement, roughly 10-15% lower than the first interval. Remember, you can estimate your VO2max from a race performance using a Running Calculator. (Note that the more recent versions of the Norwegian Method use Medium Intensity High Volume Intervals.)

4.2.1 4x4 Conversion Details

The study had athletes with average VO2max of 37, average weight of 72 Kg, and average peak power output of 260w, which is 3.6 w/Kg. A Stryd based study[6] showed that there's a linear relationship between VO2max and peak power. (Peak power at VO2max varies with protocol). For this study, the peak power in w/Kg is VO2max * 0.097.

4.2.2 4x4 Effort Worked Example

Assume your VO2max is 53 and your weight is 60, then the initial target power is 53 * 0.097 * 60 = 309 watts. So the target range would be 260-309w at the start of the interval. Alternatively, the required pace is 0.097 * 60 = 5.14 meters/second, so the range is 4.37 to 5.14 m/s. That converts to 3:49-3:14 min/Km or 6:08-5:13 min/mile. The power or pace is then dropped to keep your heart rate below 95% max.

4.3 Wingate

This style of HIIT is based around the Wingate test, which is used to measure peak anaerobic power and anaerobic capacity[7].

4.3.1 The Wingate Test

The Wingate Test typically uses a warmup of 10 minutes easy cycling, followed by 2-3x 15 second sprints to get used to the speed. Then the test is normally 30 seconds all out sprinting, though some researchers use a longer period of 40-120 seconds.

4.3.2 The Test on a Smart Trainer

The test is performed on a mechanically braked cycle ergometer, often a Monarch model. This makes converting the settings to a smart trainer tricky. The Monarch uses a weight to provide the resistance, and the Wingate Test uses 7.5% of your body weight. The formula for working out Watts for the Monarch is the resistance in Kg multiplied by the cadence. So, if you weigh 60 Kg, 7.5% is 4.5Kg, and at a cadence of 80 rpm is 360 watts. Setting your smart trainer's resistance so you get about 360 watts at 80 rpm is a good starting point for the test.

4.3.3 The Wingate as HIIT

The Wingate HIIT uses 30 seconds of 'all out' intensity, followed by ~4 minutes of recovery, repeated 4-6 times. A similar warmup procedure as the test seems reasonable, with 10 minutes easy, then 2-3x 15 second sprints.

4.4 WinTab (Tabata style Wingate)

Most athletes that use the Tabata workout do not use the 170% V̇O2max intensity, but rather the Wingate style 'all out' intensity. Because the intensity is not fixed, the WinTab normally has 8 repetitions of 20 seconds all out plus 10 seconds rest, taking 4 minutes (plus Warmup), rather than the variable number of repetitions of the original Tabata protocol.

4.5 HillTab

Because the WinTab workout involves such fast paces, it can easily lead to injury as the stride length requires a greater range of motion than more common paces. You can reduce the pace while maintaining the intensity by running up hill, something I call HillTab (Hill Tabata). While similar to the WinTab in some ways, this workout has a variable length recovery, as you have to run down the hill after each time, and it uses different muscle groups. To perform a HillTab, find a hill that is moderately steep; about 10-12% gradient works well. Find a marker to use as the start point, such as a suitable tree or rock, then find an initial finish marker that is about 45 seconds up the path. You'll adjust the finish marker so that it takes about 30 seconds to cover the distance at your fastest speed. This will take a bit of trial and error, but don't worry if the first few intervals are too long or too short. You could use an audible timer, but I prefer a visible marker to aim for. If you want to time each interval, have a watch in your hand, held so you can press the lap button without fumbling. For each interval:

  1. Approach the start marker at an easy pace.
  2. A few yards/meters from the start, shorten your stride and increase your Cadence. Your stride will be quite short at this point.
  3. As you approach the start marker, lean forward so that your weight feels over the balls of your feet and toes.
  4. When you cross the start marker accelerate hard, grabbing the ground with each stride and propelling yourself forward. You'll accelerate to your maximum velocity within a handful of strides, and you'll probably be acutely aware of each footstep as the adrenaline seems to slow time. For the first few intervals this phase often has a wonderful sense of euphoria and power.
  5. Try to hold on to this pace to the end marker, which may seem to grow further away. Your legs will grow weak and distant as the lack of oxygen causes your vision to fade to gray.
  6. By the time your reach the end, just 30 seconds later, your lungs are starting to burn and the ecstasy you felt just moments ago has turned to desolation.
  7. Slow up carefully after the end marker. Do not let your form collapse or your feet slap the ground.
  8. When your pace has dropped, turn around and descend. You may find your lungs burn more after the interval than before as you start to recover.
  9. Run past the start marker, turn and repeat for a total of 8 intervals.

For HIIT, I suspect that the hard acceleration is a key to the benefits of the workout. The acceleration achieves high levels of muscle activation, mimicking the effects of Plyometrics. (There advantages to Downhill Running, but the risk of injury while running at HIIT pace downhill are much higher.)

4.6 Traditional Anaerobic Intervals

High intensity Interval Training has been in use since before the Tabata study made the term popular. The Jack Daniel's 'R' paced workouts are a classic example of this tradition of anaerobic interval training. The Jack Daniel's 'R' intervals are performed at around mile/1500m pace[8], which is generally close to 100% V̇O2max. The 'R' workouts are 12-40 repeats of 30-60 seconds with 1-4 min rests[9]. Jack Daniels mentions once having his athletes perform over 1,000 repetitions of one-minute HIIT (4-minute rest) in a 14-day period, with two male athletes averaging 5:00 min/mile pace and therefore covering 250 miles[9].

5 Fellrnr's Tabata Audio

I created a short audio file for my Tabata (WinTab), adding a countdown and interval counts. I started with Darude's Sandstorm, remixed it to 180 BPM and then extracted short snippets. I then recombined the snippets with voice countdowns so that I didn't need to look at a watch or timer to execute the workout. You can download or play the MP3 file of Fellrnr's Tabata. (I believe that I'm making fair use of Darude's work, given I am only using a short section of the original and modifying it heavily. If you want to enjoy the overall song, this MP3 file is not it!)

6 HIIT Training Methods

There are various ways that HIIT could be performed, each with their own pros and cons. As this site is dedicated to running, my assumption is that you're a runner primarily. If that's not the case, then you'll have to interpret the pros and cons slightly differently.

Mode Pros Cons
Stationary Bike HIIT
  • A stationary bike is much safer than writing outdoors at extreme intensities.
  • The many studies have used a stationary bike to perform HIIT.
  • Riding out of the saddle is closer to moderate running in terms of muscle usage than riding seated.
  • A direct measure of intensity through power is often possible.
  • Lowest risk of injury.
  • The bike doesn't use the same Muscles as running, nor the same range of motion.
  • There is no eccentric component to cycling.
  • The specific muscles recruited will vary depending on how much you pull up on the pedals as well is pushed down.
Outdoor Bike
  • Should be similar to the stationary bike, but at a lower cost.
  • It's easier to ride a bike out of the saddle than a stationary bike, which uses more muscles and is closer to the action of running.
  • Riding a bike at high intensity adds risk due to impaired mental functioning and coordination.
  • While it's possible to directly measure power output on a bike, it's expensive.
Running on the flat
  • For runners, roughly the right muscle groups are trained.
  • With Stryd it's possible to get a good measurement of pace, and even an estimate of power output. (The estimate of running power is not equivalent to cycling power, which can actually be measured rather than estimated.)
  • At high Intensity, the movements involved in running become dramatically different, requiring a greater range of motion. This difference creates a significant risk of injury. It also changes the muscles used compared with running at submaximal intensity.
  • The rapid acceleration and deceleration of HIIT creates stress that runners are not typically exposed to, again creating a risk of injury. (I suspect the risk of injury during the deceleration is often underestimated, as this is when where a runner's form often deteriorates.)
Running up hill
  • Running uphill generates a much higher intensity at a slower pace. This means that the biomechanical changes are not so extreme, reducing the risk of injury.
  • Running uphill uses somewhat different muscles to running on the flat, so the training stress is not identical.
  • It's hard to find a hill that's long enough to do a high intensity interval training session that includes only partial recovery.
  • Getting the right incline is a tricky balance. Too shallow, and you may as well be running on the flat. Too steep and your biomechanics become exaggeratedly different.
Running with extra drag
  • It's possible to use a Running Parachute, or drag a tire behind you to increase intensity at a slower pace.
  • The slower pace means a less extreme stride length and biomechanical changes, reducing risk of injury from those changes.
  • The additional track creates radically different muscle recruitment patterns.
  • For a full list of downsides see Running Parachutes.
Treadmill
  • It's possible to run in weather that is too hostile for outside activities.
  • Most treadmills will not change pace fast enough for the dramatic changes in pace between interval and recovery used in HIIT.
  • Matching acceleration and deceleration with the treadmill is not easy, especially when mental functioning is impaired, as it so often is at high intensity
  • If you cannot maintain the programmed pace, you could be injured by falling off the back of a treadmill.
  • A treadmill may not be able to go fast enough for HIIT.

7 HIIT Running Paces

I don't generally recommend running HIIT workouts because of the high speeds required. Below is a sampling of the HIIT paces for different fitness levels (V̇O2max). For each level, the 5K and marathon times are given, along with the pace that corresponds to 90%, 100% and 170% of V̇O2max.

V̇O2max 35 40 45 50 55 60 65 70 75 80 85
5K 26:57 24:05 21:50 20:00 18:28 17:10 16:03 15:05 14:15 13:32 12:51
Marathon 4:15:51 3:49:27 3:28:10 3:10:33 2:55:49 2:43:08 2:32:29 2:23:04 2:14:53 2:07:31 2:00:58
90% V̇O2max 9:09/Mile 8:13/Mile 7:28/Mile 6:52/Mile 6:21/Mile 5:55/Mile 5:33/Mile 5:13/Mile 4:56/Mile 4:41/Mile 4:27/Mile
100% V̇O2max 8:24/Mile 7:33/Mile 6:52/Mile 6:18/Mile 5:50/Mile 5:26/Mile 5:05/Mile 4:47/Mile 4:32/Mile 4:18/Mile 4:06/Mile
170% V̇O2max 5:28/Mile 4:54/Mile 4:27/Mile 4:06/Mile 3:48/Mile 3:33/Mile 3:19/Mile 3:08/Mile 2:58/Mile 2:49/Mile 2:41/Mile

8 HIIT and Stryd

The Stryd footpod gives an extremely accurate measure of pace and incline, and from this it calculates an estimate of your power output in Watts. This power estimate responds much faster than Heart Rate, which is pretty useless for evaluating a HIIT session.

A graph of Heart Rate against Stryd power estimate for a HIIT session.

9 The HIIT Science

For details of the science around HIIT, see The Science of High Intensity Interval Training.

10 Crossfit Endurance

Crossfit Endurance is a training approach that reduces the normal endurance training volumes while increasing the training intensity[10]. The reduction in volume is quite dramatic compared with other training plans; for instance, the Crossfit Endurance marathon training plan has a 10 mile time trial as its longest run, which is combined with weight training and interval training[11]. Crossfit Endurance claims that eight 100 meter intervals "accomplishes everything you would by jogging 20 miles but doesn't put the same level of stress and damage on the body." There is the caveat that "some kind of stamina work that lost more than the 70 seconds is required to "dial in technique, just rhythm, and formulate pace strategy." While there are some testimonials to the Crossfit Endurance methodology[12], their approach is controversial[13]. The science that is used to support Crossfit Endurance does not support replacing traditional Continuous Moderate Exercise with HIIT for endurance events, only using HIIT as a supplementary form of training[14]. Most of the anecdotal reports suggest that people have set personal records at 5K and 10K distances and completed half marathons using the Crossfit Endurance approach, but there are few reports of longer races. The anecdotal reports are hard to interpret objectively without knowing the individuals prior training methodology. (I have some other concerns with CrossFit, such as their emphasis on forefoot landing, then approach to hydration that includes the overly simplistic "sweat rate test", but that's outside of the scope of this article that focuses on interval training.)

11 References

  1. ↑ Stephen H. Boutcher, High-Intensity Intermittent Exercise and Fat Loss, Journal of Obesity, volume 2011, 2011, pages 1–10, ISSN 2090-0708, doi 10.1155/2011/868305
  2. ↑ EG. Trapp, DJ. Chisholm, J. Freund, SH. Boutcher, The effects of high-intensity intermittent exercise training on fat loss and fasting insulin levels of young women., Int J Obes (Lond), volume 32, issue 4, pages 684-91, Apr 2008, doi 10.1038/sj.ijo.0803781, PMID 18197184
  3. ↑ MJ. Gibala, JP. Little, M. van Essen, GP. Wilkin, KA. Burgomaster, A. Safdar, S. Raha, MA. Tarnopolsky, Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance., J Physiol, volume 575, issue Pt 3, pages 901-11, Sep 2006, doi 10.1113/jphysiol.2006.112094, PMID 16825308
  4. ↑ J. Helgerud, K. Høydal, E. Wang, T. Karlsen, P. Berg, M. Bjerkaas, T. Simonsen, C. Helgesen, N. Hjorth, Aerobic high-intensity intervals improve VO2max more than moderate training., Med Sci Sports Exerc, 39 !!V̇olume!!, issue 4, pages 665-71, Apr 2007, doi 10.1249/mss.0b013e3180304570, PMID 17414804
  5. ↑ Justin J. Acala, Devyn Roche-Willis, Todd A. Astorino, Characterizing the Heart Rate Response to the 4 × 4 Interval Exercise Protocol, International Journal of Environmental Research and Public Health, publisher MDPI AG, volume 17, issue 14, date 2020-07-15, ISSN 1660-4601, doi 10.3390/ijerph17145103, page 5103
  6. ↑ https://blog.stryd.com/2019/12/06/how-to-use-stryd-power-to-calculate-your-vo2/, How to use Stryd power to calculate your VO2, Accessed on 2023-08-21
  7. ↑ H. Vandewalle, G. Pérès, H. Monod, Standard anaerobic exercise tests., Sports Med, volume 4, issue 4, pages 268-89, PMID 3306867
  8. ↑ Jack Daniels, Daniels' running formula, date 2005, publisher Human Kinetics, location Champaign, IL, isbn 0-7360-5492-8
  9. ↑ 9.0 9.1 Jack Daniels, Daniels' running formula, date 2005, publisher Human Kinetics, location Champaign, IL, isbn 0-7360-5492-8, pages 132
  10. ↑ About Crossfit Endurance, http://www.crossfitendurance.com/whatiscfe, Accessed on 26 February 2013
  11. ↑ http://www.outsideonline.com/fitness/endurance-training/CrossFit-Endurances-Unconventional-12-Week-Marathon-Training-Plan.html, http://www.outsideonline.com/fitness/endurance-training/CrossFit-Endurances-Unconventional-12-Week-Marathon-Training-Plan.html, Accessed on 26 February 2013
  12. ↑ Testimonials, http://www.crossfitendurance.com/testimonials, Accessed on 26 February 2013
  13. ↑ Science of Running: Crossfit endurance, Tabata sprints, and why people just don’t get it, http://www.scienceofrunning.com/2012/01/crossfit-endurance-tabata-sprints-and.html, Accessed on 26 February 2013
  14. ↑ CrossFit MPH - Washington, DC, http://metamorphitness.wordpress.com/nutrition-enrichment/running-faqs/is-there-any-science-to-support-crossfit-endurance/, Accessed on 26 February 2013
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