How Often To Run
There is a natural human belief that if some is good, more is better. This idea is all too often false, and can be destructive with training. There's an old adage that "running does not make you a fitter, it's the rest that follows running that makes you fitter". Getting the right balance of running and rest is a critical part of your training, and there are a number of factors to consider. I've reviewed the available research (see below) and literature to come to some initial conclusions.
- While it's quite possible to do the same run every day, this type of training isn't generally effective at improving fitness. The only training plans I'm aware of that train the same every day are for beginners just learning to run.
- Most training plans have at least a mix of easier and harder workouts, as well as some rest days. Only FIRST attempts some level of scientific validation, but even this plan doesn't seem to take into account the available research.
- Because running includes an eccentric component (see below) it is quite different to cycling and swimming. There is clear scientific evidence, as well as plenty of anecdotal that excessive eccentric exercise can take many weeks to recover from. This is shown most clearly in longer runs and downhill running, where runners can struggle to walk down stairs for days after a marathon. One way of looking at this is that a longer period is needed to recover from long and/or downhill runs. However, it's probably better to focus on building up the long and/or downhill runs so that the recovery period is reasonable.
- Shorter distance running, even at race effort, can be recovered from quite quickly in well trained runners. Race distances of 5-10Km could be recovered from in 2-3 days, though this time is likely to be longer in slower and/or less established runners. (For slower runners, the duration becomes longer, increasing eccentric stress, and less established runners will have less Delayed Onset Muscle Soreness resistance.)
- High Intensity Interval Training may require the least recovery time, thought this is likely to be highly dependent on the mode and load. I recommend using a stationary bike for HIIT to reduce injury risk and to precisely control the workout. It seems that for some modes of HIIT, recovery can be as short as 24 hours.
- Easy running or training between hard workouts doesn't seem to have any support in the research.
Putting this together, it suggests a workout plan should fit this outline.
- Endurance training through long and/or downhill running should be built up carefully so that soreness lasts 2-4 days, with the gaps between the endurance runs about 3 times the length of the soreness.
- HIIT workouts or short/fast runs about 3 times/week. (HIIT could be more frequent.)
- 1 Supercompensation
- 2 Long and Downhill Running
- 3 The Science of Recovery
- 4 The Science of Measuring Recovery
- 5 The Science of Training Frequency
- 6 The Science of Active Recovery
- 7 Training Plans
- 8 Advanced Topics
- 9 See Also
- 10 References
It's well accepted that exercise is a critical part of improving fitness, and there are many different Endurance Adaptations that occur. The primary mechanism for these adaptations is that exercise causes damage and this damage is repaired to be stronger than before the exercise. This is seen in the fatigue that occurs after exercise, and the need for rest. The term for this mechanism is Supercompensation, and is a key principle for creating training programs.
2 Long and Downhill Running
The recovery required for longer or downhill running incurs more Delayed Onset Muscle Soreness (DOMS), which has a much longer recovery time. Most training plans have longer runs every 7 or 14 days, but the research suggests that the actual recovery period will depend on the severity of the DOMS. Recovery periods could be as long as 30-90 days, which is obviously so long that detraining is likely. In practice, I believe that we need to invert the problem. Instead of working out the recovery period for the long/downhill running, we need to optimize the running impact so that recovery occurs in the right time period. A long/downhill run that produces performance deficits that are not resolved well before the next long/downhill run are too stressful and the effort needs to be reduced.
3 The Science of Recovery
Below are the studies I've found looking at the timeline of recovery from exercise stress. Overall, the time to recover from varies enormously between different types of training and different subject groups. My conclusions from the research are that HIIT can be recovered as quickly as 24 hours, short race distances in 48 hours, but marathon, ultramarathon, and DOMS inducing exercise can potentially take weeks to recover from. Importantly, subjective feelings of recovery seem to be inadequate in evaluating the actual recovery.
3.1 Recovery from Eccentric and Downhill Exercise
Because running always involves an eccentric component, this modality is quite important as it produces DOMS. The eccentric component is particularly important for endurance running, especially when it includes downhill running. The immediate muscular weakness that occurs with eccentric exercise compromises performance in longer runs. The repeated bout effect, which provides significant subsequent protection from DOMS has to be carefully balanced with the potentially elongated recovery periods. The research suggests that recovery can take many weeks, something that is likely to produce impaired subsequent training.
- A study of 192 subjects undergoing eccentric muscle damage found that recovery was extremely protracted. The eccentric damage resulted in peak force being reduced to 43% of the pre-exercise level immediately after the exercise. There was no recovery at 36 hours, and by 132 hours (5.5 days) they were still reduced by 33%. Of the 32 subjects that had their peak force reduced to <30% of their initial levels, 20 were retested after 26 days and had only regained 81% (males) and 93% (females.) A further subset of 9 subjects did weekly testing that recovery took between 33 and 89 days! This suggests that recovery from eccentric exercise can be extremely protracted, and that the "eccentric dose" needs to be built up carefully.
- Ten soccer playing students with an average V̇O2max of 54.6 were evaluated before and several times after performing 30 minutes of downhill running. They ran downhill at -15%, a fairly steep gradient, with speed set to 70% V̇O2max. Maximum strength was reduced by an average of 21%, 1 hour after the descent and recovered slowly until day 5 when they were back to normal. Muscle soreness peaked on day two, and returned to near baseline (no soreness) by day 5. Interestingly, creatine kinase (CK), a marker of muscle damage remained elevated for the 5 days of the study (~420-460 U/l.) Their Running Economy was impaired from 1-hour post descent through to day 3 at speeds varying from 65% to 85% of V̇O2max, but returned to baseline by day 4. Likewise, many other markers such as respiration, and heart rate were elevated though to day 3, returning to baseline at day 4. This suggests that as little as 30 minutes of downhill running produces noticeable muscle soreness will create impairment for 3-5+ days, and that muscle soreness is not a reliable indicator of recovery.
- A shorter study of 9 well trained runners and triathletes found that 30 minutes of downhill running at 70% V̇O2max resulted in impaired Running Economy 48 hours. Unfortunately, no other time periods were evaluated, but this study also suggests recovery from downhill running lasts more than 2 days.
- A study of 14 fit, active subjects underwent 45 minutes of downhill running at 10 degrees (17.6%) and evaluated before, after, then at days 1, 4, and 7. They found that the CK marker of muscle damage was elevated for the first day, returning to baseline at day 4. The study found that CK levels were higher after running in cold (5c) rather than warm (22f) conditions. The CK levels were quite high, peaking at nearly 1,200 U/l. This study suggests that recovery from downhill running could be much shorter than other studies.
- A study looked at 10 female runners, V̇O2max 48 (42-56), who underwent 30 minutes of downhill running at 74% of Max HR and -15 degrees (26.8%). The runners had no change in Running Economy 2 or 5 days later, which is a little surprising given the steepness of the downhill running. Looking at the results, muscle soreness was higher on day 2 but near baseline on day 5, though the scale is not clear. The CK values were elevated on both days, but the levels were lower than in other studies, reaching 150 on day 2 and 106 on day 5. By comparison, another study had CK values of well over 400. This suggests the runners were accustomed to downhill running, which creates a large protective effect from Delayed Onset Muscle Soreness.
- A study looked at 50 male students (V̇O2max 55 +/-6) underwent 30 minutes of downhill running at 15% (8.5 degrees) at 70% V̇O2max. Muscle soreness peaked after 1-2 days and lasted 4 days, while muscular weakness peaked at 20% down immediacy after the downhill, but was still down by 5% after 7 days. CK peaked around 1-2 days, but was still elevated at day 7. Running Economy was reduced by 5% after two days and was reduced by 2% after 7 days. This suggests that the impact of downhill running can last more than 7 days.
3.2 Recovery from High Intensity Interval Training Recovery
There is some indication that recovery from HIIT can occur in as little as 24 hours. It seems likely that different modalities of HIIT will produce different recovery periods, but it also seems likely that recovery from effective HIIT can be far faster than other forms of training.
- A study of netball players looked at their recovery from a simulated game. The players underwent performance testing before and after simulated games on two consecutive days. The simulated game involved sprinting and I believe is close to High Intensity Interval Training. The study used various recovery protocols lasting 15 minutes after each simulated game, with no differences found between interventions. Of interest here, there was no degradation in performance between days. This suggests a rapid recovery, within a day, from HIIT.
- A similar study using a simulated rugby game, repeated after 24 hours found no performance differences on the second day. The simulated rugby game was an 80-minute-long, high-intensity exercise circuit, and performance determined by repeated 20-m sprints and peak power. This study also suggests recovery from HIIT within a day.
- A study of 10 healthy volunteers compared to training protocols that were identical other than the frequency of training. Both protocols used 30 seconds of maximal cycling with 12-minute recovery periods (unusually long), and the number of repetitions was increased during the study as the subjects became fitter. Both groups performed 14 training sessions. In one group, the subjects trained every day for 2 weeks, while the other group had two-day rest periods between each training session, spreading the 14 sessions over 6 weeks. The subjects without rest days did not improve either average or peak power during a 30-second Sprint test, while the subjects that did have rest days improved both of values. This could mean that rest days between HIIT sessions are good idea, or it could mean that it takes more than two weeks to see the benefit of this type of training.
- Most studies of The Science of High Intensity Interval Training use 3 or 4 sessions per week, but there is rarely a control using other training frequencies. This suggests that 3 or 4 sessions per week is effective, but there's no indication of what is optimal.
3.3 Recovery from Short Race Distances
The research into shorter distances suggests that even race efforts at 5-10Km can be recovered from in 48-72 hours.
- A directly relevant study for runners looked at recovery from a completive 10Km track race. The 10 male subjects were former collegiate athletes, and their 10Km times averaged 35 minutes with other indications this was an "all out" race effort. Immediately after the race there was some impairment of force production in the hamstrings, but not the quads. This hamstring impairment is believed to be predominantly in slow twitch fibers with fast twitch remaining unaffected. Both hamstrings and quads fatigued more quickly after the race compared with prior. After 48 hours, most measurements have returned to pre-race levels, though the hamstrings still fatigued more quickly, only recovering about half of the prior capacity. This suggests that 48 hours is sufficient to mostly recovery from a 10Km race.
- A study of 12 well trained runners (9 male) looked at their recovery from a 5Km time trial. Runners performed the 5Km time trial and then either had 24 hours or 72 hours of rest before doing another 5Km time trial. The average time for the first 5Km was 19:49 (16:41-22:18), so these were reasonable, but not elite runners (V̇O2max was 63 for the men and 60 for the women.) The 5Km time after only 24 hours recover was 10 seconds slower (p=0.03) while the time after 72 hours was not different from the baseline run. Notably the runners felt the same before each run, both in terms of soreness and fatigue, so the degradation was not noticeable to the runners. This suggests that 24 hours is insufficient for recovering from a 5Km time trial, while 72 hours adequate. It also suggests that subjective feelings of recovery may be misleading.
3.4 Recovery from Marathons
The research shows a wide variation in recovery times from a marathon, with as little as 5 days to greater than 7 days. No studies checked for longer than 7 days, which means we have no indication of the upper limit. My personal experience is that recovery from a marathon can often take more than 14 days for those unused to the distance, but with practice, recovery can be as short as 48 hours. Much of the difference seems likely to do with resistance to DOMS that occurs with repeated bouts.
- A 1984 study of 10 marathon runners looked at their recovery. The runners had previously run marathons, but not in the previous 6 months and trained an average of 104Km/~60miles week in the 3 months leading up to the race and all achieved personal bests in the race. They had a V̇O2max of ~68 and marathon times around the 3-hour mark. The runners were tested before, ~20 minutes after the race, then at 1, 3, 5, and 7 days post-race. The runners were split into two groups, with one resting and the other did "active recovery" of easy (50-60% V̇O2max) runs for 20, 25, 30, 35, 40, 45 minutes each day post-race. Ratings of perceived soreness peaked on the first day and returned to baseline (no soreness) by the 5th day, with no differences in soreness between the two groups. Work capacity measured over 50 leg extensions was reduced in both groups on day one to the same level. Work capacity didn't improve in the rest group on day 1 after the marathon, while the active group recovered partly. On days 3, 5, 7 the active group did not recovery work capacity any further, while the resting group regained all the lost work capacity. A similar result occurs with the maximum strength, with the active recovery group regaining less strength than the rest group. However, both groups were still below their pre-race maximum strength after 7 days. While this is a small sample size, this suggests that recovery from a marathon race can occur within 7 days if the runner rests, and it suggests that muscle soreness is not a good measure of recovery.
- A test of compression garments found that maximum strength was impaired at 48 hours after a marathon, but returned to baseline after 72 hours, though markers of muscle damage (CRP) were still elevated at 72 hours. However, there was wide individual variability in the time course of both strength and muscle damage markers. This suggests that some runners can recover strength from a marathon within 72 hours, even though markers of muscle damage remain.
- A study of the impact of a marathon on muscle fiber damage (necrosis) in 10 male marathon runners found the damage lasted at least 7 days. The study used biopsies pre-race, post-race, then days 1, 3, 5, and 7. The damage was most prevalent on days 1 and 3, but persisted to day 7. This damage appears to be very similar to Delayed Onset Muscle Soreness, but unfortunately there were no samples after day 7 to indicate when full recovery occurred. (The runners' times varied between 2:31 and 3:39.) This suggests that recovery from a marathon may not be complete in some runners after 7 days.
- A study on eight elite male marathon runners found that maximum voluntary contraction was reduced post marathon race (2:34 average time), but recovered by five days. Rather strangely, Running Economy at marathon pace was impaired immediately after the race, but two- and five-days post-race their RE was better than before the race. This suggests that some runners (including elites) can recovery from a marathon in less than five days.
- A study of 7 experienced triathletes (6 male) were evaluated before, during, after 2 hours, then after 2, 4, and 6 days following a marathon distance treadmill run. Their Running Economy fell during the run, and was impaired at 2 h (14%), 2 days (10%), 4 days (2.4%), and 6 days (2.4%) post marathon. CK was elevated after the marathon, returning to baseline at day 6. This suggests recovery from a marathon can take longer than 6 days.
- A study of 7 runners in the 1979 Stockholm Marathon found that they had predominantly depleted the Glycogen in slow twitch fibers of the quad, and they had reduced fatigue resistance but not reduced maximum strength. The runners finished the marathon between 2:22 and 3:30. Another group of 10 subjects used a combination of 30 min cycling, 75 min running and sprinting to reduce the glycogen of both fast and slow twitch fibers, resulting in both reduced fatigue resistance and reduced maximum strength immediately after the exercise. This doesn't indicate the timeline for recovery, but shows that a marathon race produces muscular weakness.
3.5 Recovery from Ultramarathons
There is even less research into ultramarathons than marathons, but not surprisingly, recovery from an ultramarathon effort can be protracted. It's unclear if ultramarathons can produce an improvement in fitness. It seems probable that some aspects of fitness may improve (such as DOMS resistance), but some detraining may occur during the protracted recovery.
- A study of runners in the 90Km/56-mile Comrades Marathon found Running Economy was reduced for the 32 days after the race, though only day 25 was statistically significant. Muscular strength as measured by jumping was reduced for 32 days, though only statistically significant for 3-18 days depending on the jump type. The study only included 8 runners, so statistical power was low. This suggests that recovery from an ultramarathon can take up to 32 days.
- A study of 72 runners at the 100 mile/161Km Western States Endurance Run found 400m run time was slower 3- and 5-days post-race, while muscle soreness peaked on race day and gradually declined over the following 7 days. Subjective muscle fatigue peaked immediately post-race and returned to near baseline by 7 days post-race. This suggests that recovery from an ultramarathon can take more than 5 days.
3.6 Recovery from Strength training
There are many studies on strength training, but the one below is noteworthy as it calls out the time supercompensation. After all, maintaining baseline performance is not the goal of training.
- A 2003 study of the recovery from strength training showed the time course for Supercompensation . The 30 male subjects were experienced in strength training, having used a protocol of training 3-4/week for at least 12 weeks. 20 were in their 20s, 10 in their 50s. The exercise was 7 sets to failure for the older men and half of the younger, or 3 sets to failure for the remaining 10 younger men, each over 8 muscle groups. All subjects were weaker after 24 hours, with performance returning to baseline after 48 hours, with Supercompensation to above baseline at 72 hours. This suggests that 48 hours may be insufficient for optimum recovery from strength training. This is study suggests that supercompensation can occur in 72 hours after strength training when recovery to baseline is complete within 48 hours.
4 The Science of Measuring Recovery
A key problem in knowing how frequently to train is measuring recovery. It seems intuitively obvious that different modes of training and different training loads will result in different recovery periods. Running an easy mile will result in no appreciable need for recovery, while running hilly 100-mile race could leave me impaired for weeks.
- A common approach in research is to use maximum strength or maximum power output as a measure of recovery. This seems to be one of the best measures, but obviously the test itself incurs a training load. It seems possible that a short test, using a brief (2-3 minute warm up) followed by 20-30 seconds "all out" might provide insight into recovery without significant training stress on the athlete.
- Using blood markers, such as creatine phosphokinase (a marker of muscle damage) can be used to track the impact of exercise and recovery. Of course, this is of little use outside of a research context.
- There's been a lot of interest in using Heart Rate Variability (HRV) for measuring training stress and recovery. However, I've never seen any relationship between HRV and my training/recovery status. A study of 57 elite Nordic-skiers over five years also found no relationship between HRV and training load.
5 The Science of Training Frequency
There's relatively little research that goes beyond recovery into training frequency and recovery from repeated bouts. There are some indications that lower frequencies might be more effective it's hard to be more definitive. Based on the research above on recovery, it seems likely that the specifics of the exercise may have a huge impact on the appropriate frequency.
- A study of six untrained subjects looked at how training frequency effected both recovery and gains in fitness. The study used intermittent cycle training three times per week for 8 weeks (low frequency) followed by a week without training, followed by training five times per week for 4 weeks (high frequency). The study then fitted their recovery measured using the maximum power over 5 minutes into a mathematical model. The low frequency training subjects recovered in 0.9 days, but the high frequency took 3.6 days to recover. In addition, the high frequency training produced lower benefits from the training effort. The main flaw in this study is that the high frequency training follows the lower frequency training, so the subjects have improved their fitness, which normally results in a slower fitness improvement. This study suggests that training 5/week impairs recovery compared with 3/week, but the study flaws means this could be an artifact of the design.
- A 1986 review of 30+ studies looked at training to improve V̇O2max . The study found that across all fitness levels and intensities, fitness improvements increase with training frequency up to 6/week (no study looked at 7/week.) For lower fitness individuals (V̇O2max 30-40), improvements were proportional to frequency, with 2/week producing improvements, but 5-6/week being most effective. For V̇O2max 40-50, training for 4/week or 6/week seemed to be most effective. Finally, for V̇O2max 50-60, 3/week might be the most effective. However, the wide disparity in the protocols of the underlying studies creates means the results have to be used with caution.
6 The Science of Active Recovery
Active recovery is the idea that low intensity exercise improves recovery from high intensity exercise. In the context of easy exercise on the day after hard exercise, one study found that indicated that active recovery does nothing to help. Another found that active recovery after a marathon significantly impaired strength and work capacity, even though muscle soreness was gone. An analysis of the evidence on active recovery noted that "evidence that active recovery enhances recovery between training sessions is currently lacking". A study looked at the recovery from downhill running in 50 male students (V̇O2max 55 +/-6). The runners either rested or ran for 30 minutes each day for 6 days. The post-downhill runs were at 40%, 50%, 60%, or 70% of V̇O2max. There were no differences between rest and running in measures of muscle soreness or Running Economy.
6.1 Other Uses of the Term "Active Recovery"
Note that "Active Recovery" can have other meanings:
- 'Active Recovery' can also refer to doing low intensity exercise between the work periods of Interval Training, which is effective as it metabolizes lactate and speeds up the short-term recovery needed before the next interval. Active recovery also limits the additional cardiac stress that occurs when you stop running as the muscle compressions help venous return to the heart, maintaining blood pressure.
- Doing gentle exercise immediately after intense exercise as a Cooldown may have some benefits. There is anecdotal evidence that walking for 20-30 minutes after a Long Run reduces muscle soreness.
7 Training Plans
The FIRST plan is based around running three days a week, and is the only plan I am aware of that has undergone scientific evaluation about its effectiveness. Hal Higdon's Advanced II Marathon plan has 6 days of running, but two days are trivial. Jeff Galloway uses four days/week. The Runner's World beginners plan is four days/week. (The RW intermediary & advanced are 5 days.) Jack Daniels defines just two work outs a week, and leaves it up to you how you fit in the other miles.
8 Advanced Topics
8.1 Overload Training
Running hard or long everyday will build up cumulative fatigue as the body does not have sufficient time to recover. If this is kept up to long, then some type of failure will occur; either injury or some form of Overtraining. However, it is possible to run for a number of days consecutively, building up deeper cumulative fatigue, and then taking a longer rest period. This is one of the principles of the Three Phase Taper.
8.2 Multiple Workouts Per Day
Running 3 or 4 days/week does not mean running at most once per day. It can be effective or necessary to run more than once per day while running fewer days per week. Running more than once in a day can provide some of the training stress of a single longer run.
9 See Also
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