Tempo Runs, the least effective form of training

A tempo run, sometimes called a threshold run, is a common part of many training programs as coaches believe it is an effective way of improving lactate clearance. However, the science indicates that tempo paced runs should be avoided in favor of other paces. Tempo pace represents the no man's land between Long Slow Distance and High Intensity Interval Training. They are too fast to be long, and too slow to be intense. They can improve performance in the untrained, but not as well as other types of training and so they are the least effective form of training. In fact, for highly trained runners there is evidence that Tempo Runs may be counterproductive. While there are claims that Tempo Runs have benefits for Mental fortitude this is not supported by the science that has looked at race performance. Note that performing intervals at Tempo, Threshold, or other sub-maximum effort can be considered Medium Intensity High Volume Intervals rather than a tempo run, which is typically continuous.

1 What is a Tempo Run?

A Tempo Run intended to be run at or near the pace corresponding to the Lactate Threshold. Lactate Threshold can be thought of as the transition from mostly aerobic to mostly anaerobic metabolism. In well trained athletes, paces below the Lactate Threshold can be kept up for prolonged periods (several hours), where paces about the Lactate Threshold typically cannot be maintained for more than an hour. The specific definitions vary a little, as it's tough to measure Lactate Threshold, more properly called "Maximum Lactate Steady State" or MLSS (See Lactate Threshold for more details.) Some example definitions:

• Jack Daniels defines Threshold Pace as 83-88% of V̇O₂max, or 88-92% of your pace at V̇O₂max, or 88-92% of Maximum Heart Rate, which he intends to be MLSS pace.
• The FIRST training plans use a pace slightly slower than 10K pace or marathon pace.
• The Hanson's Marathon Method uses marathon pace for tempo runs.

2 The Tempo Myth

There is a prevalent myth that Tempo runs are an important part of a training program. The idea is that running at Lactate Threshold pace improves Lactate clearance and thus improves performance.

• Jack Daniels, author of Jack Daniels Running Formula says "Threshold, or T-pace, running is one of the most productive types of training that distance runners can do".
• Hal Higdon in "Marathon The Ultimate Training Guide" says "Exercise scientists now tell us that doing tempo runs is the most efficient way to raise your lactate threshold - that is, your ability to run at a fast pace without accumulating lactic acid in the bloodstream".
• Matt Fitzgerald in his book "Run Faster" says "Threshold training is a major part of every running coach's training system", and that "Threshold runs … stimulate aerobic-system adaptations and other physiological changes that enable runners to sustain faster and faster running paces for longer and longer stretches of time".
• It's common for scientific research to propagate the myth of the tempo run, quoting other papers that don't substantiate the claims. For instance, a 2009 research study stated "One of the most valuable exercises athletes use for developing an aerobic base is maximal steady state exercise". This study then quotes three references to back up the statement:
  • The 2003 study of elite Kenyan is hard to interpret in terms of Tempo runs, though less time spent at Tempo pace was correlated with better race performance. (See below for a more detailed analysis.)
  • A 1998 study only made vague mention of tempo runs, saying "These considerations lead us to reject the use of V-OBLA in the prescription of V-MLSS exercise training".
  • A 2002 study of cyclists makes no mention of Lactate Threshold training at all.

3 The Science of Tempo Runs

The idea that training at threshold intensity is particularly effective has no evidence. However, this is not the same as saying that tempo runs are not effective at all, just that they are not more effective than other forms of training.

3.1 Evidence in Favor of Tempo Runs

• Tempo runs can improve performance in untrained subjects. However, these studies did not compare how effective tempo runs are over other forms of training.
• A study of 9 experienced recreational masters runners showed a dramatic improvement (50%) in time to exhaustion at Lactate Threshold after interval training at Lactate Threshold pace. The runners had an average half marathon time of 83 minutes (+/-5), but had never performed any form of speedwork. Their average training before the study was five runs per week for an average of 65 minutes at 12.4 KPH (7:36 min/mile). The study lasted for 6 weeks, with 2 tempo paced interval sessions replacing 2 of the slower paced runs per week. One session was 3 intervals of 10 minutes each, the second 2 intervals of 15 minutes. Each week the shorter and longer intervals were lengthened by 2 and 3 minutes respectively. After training V̇O₂max increased 3.6% and Velocity at Lactate Threshold increased 4.2% (13.8 to 15.2 KPH, or 7:00 to 6:21). More impressively, the time to exhaustion at Lactate Threshold pace increased by a massive 50% from an average of 44 minutes before to 63 minutes after training. Unfortunately, the study did not include any form of controls to know how much familiarity with the testing procedure influenced the results, nor was there any comparison with other forms of training such as High Intensity Interval Training.
• Four weeks of tempo training increased V̇O₂max by 10% in moderately trained runners. The only control was performing interval training just above or just below tempo pace, which resulted in a smaller (6%) improvement.

3.2 Evidence Against Tempo Runs

• In recreational 10K runners, there is not as much improvement from training at Lactate Threshold as from polarized (low/high) training.
• Training at Tempo paces is ineffective for trained athletes, and may even be counterproductive.
• Moderately trained subjects trained for 3 days/week for 8 weeks using either Short HIIT, Long HIIT, Tempo runs, or LSD. V̇O₂max was unchanged in the tempo and LSD groups, but increased 7.2% in the Short HIIT and 5.5% in the Long HIIT groups.
• Training at lower intensity (blood lactate < 2 mmol/l) is more effective at improving performance at the Lactate Threshold than training at the Lactate Threshold (3-6 mmol/l).
• A 2007 randomly assigned 12 sub-elite 5K & cross-country runners to one of two training programs. The Z1 program had 80% LSD, 10% Tempo, and 10% HIIT, whereas the Z2 program had 65% LSD, 25% Tempo, and 10% HIIT. The Z1 group that did less time at Tempo pace improved their race performance more than the Z2 group. (Their simulated 10K times improved 35 seconds more, 157 second improvement rather than 121 second improvement.)
• A 2009 review of the science of training intensity noted that recreational runners typically fall into a "black hole" of too much Lactate Threshold running. They noted "Training intended to be longer and slower becomes too fast and shorter in duration, and interval training fails to reach the desired intensity. The result is that most training sessions end up being performed at the same threshold intensity."
• The performance of elite 5k/10K runners is related to total time spent in low intensity training, not higher intensities.
• Polarized training has been shown to be more effective than high volume/low intensity, threshold/tempo, or High Intensity Interval Training. The polarized training used two High Intensity Interval Training and two long (150-240 minute) low intensity sessions.
• It has been observed that elite athletes exercise 80% of the time at low intensity (blood lactate < 2 mmol/l) and 20% of the time at Lactate Threshold or High Intensity Interval Training. (Sadly this study did not have any breakdown between Lactate Threshold or High Intensity Interval Training.)
• A study of 20 elite Kenyan runners produced rather unclear results. The study categorized the runners as either high-speed training (HST) or low-speed training (LST). The 7 women did no tempo runs, and the men in the HST group used tempo runs for an average of 7% (11Km) of their training volume compared with 14% (25Km) in the LST group. The male HST group showed slight but statistically significant better performance. 10K race pace of 21.2 Km/h for HST and 20.8 Km/h for LST, Lactate Threshold pace of 20.2 Km/h for HST and 19.9 Km/h for LST, but Running Economy was better in LST (214 mL/Kg/Km in HST and 203 mL/Kg/Km in LST). However, there are many other variables that differ between the LST and HST group making meaningful conclusions on Tempo runs unreasonable.
• A 1991 study of elite runners found that they spent little of their time training at lactate threshold, something that was then considered sub-optimal. Note that this is in spite of the prevalent belief of coaches in the value of Lactate Threshold training.
• A study of rowers before the world championship found they spent the majority of their time in the rowing equivalent of Long Slow Distance (<2 mmol/l) with 4-10% of High Intensity Interval Training (6-12 mmol/l) and no training at Lactate Threshold.
• An analysis of the training of elite junior cross-country skiers found they spent 75% of their time at low intensity, 17% at high intensity, and only 8% around Lactate Threshold. The study concluded "It appears that elite endurance athletes train surprisingly little at the lactate threshold intensity."
• There is anecdotal evidence of two world class athletes that improved their performance after de-emphasizing threshold training.

4 Why Are Tempo Runs Ineffective?

The improvements in Lactate Threshold pace are largely due to a greater rate of Lactate removal rather than reduced rate of production. All muscle fibers release lactate at rest, but switch to net absorption as lactate levels rise. There is some evidence that slow twitch (endurance) muscle fibers become net consumers of Lactate at lower concentrations, and absorb more Lactate at any given concentration than fast twitch fibers. In addition, slow twitch fibers are better suited for Lactate oxidation than fast twitch, as well as having better Lactate Transport (in and out of the muscle). It seems reasonable that low intensity exercise focuses more on slow twitch fibers, and is therefore more effective at improving Lactate Threshold than higher intensities. However, I have not located any research to support that hypothesis.

5 The Norwegian Method

Main article: Medium Intensity High Volume Intervals

The success of athletes such as the Ingebrigtsen brothers, Kristian Blummenfelt, and others has created interest in the "Norwegian method". Originally, the Norwegian method seemed to mean 4x4 minute intervals at 90-95% max HR, but the meaning has changed since then. As of July 2023, the Norwegian method is based on training anecdotes of elite Norwegian athletes, with no defined formal protocol and no testing of the approach in other athletes. This makes it extremely difficult to understand, as the information is so incomplete, but a review of what's available gives some sense of the approach. These athletes use both heart rate and lactate measurements as part of their training, using lactate to guide their intensity. The value of using lactate over heart rate is unclear to me and is impractical for most athletes due to the cost. However, the key to the Norwegian method is that they seem to focus on Medium Intensity High Volume Intervals rather than Tempo runs. While the intensity is similar, the Norwegian method uses lower intensity than Tempo/Threshold pace combined with a high volume of intervals.