Sport & Performance
Rest between intervals: how long to rest, and whether to keep moving
The rest between intervals decides how much of the next effort an athlete can actually perform. For short, very hard efforts, the evidence favours longer rest and passive recovery, meaning standing still or walking slowly, because it lets people repeat more high-intensity work within a session. For longer intervals of several minutes, rest between one and four minutes made little difference to performance in trained runners, and about two minutes of easy movement was a reasonable middle ground. Over weeks of training, active and passive recovery appear to produce similar fitness gains.
What the rest period refills
A hard effort lasting seconds relies heavily on phosphocreatine (PCr), a high-energy compound stored in muscle that regenerates ATP, the molecule muscles use directly for contraction, faster than any other pathway. The store is small and empties quickly, and it is rebuilt during rest using oxygen.
A 1995 study of 14 men performing two 30-second all-out cycling sprints measured this directly with muscle biopsies in eight of them. At the end of the sprint, PCr was about 20% of its resting level. It recovered to 65% after 1.5 minutes but only to about 86% after 6 minutes, with an average half-time of roughly 57 seconds. Peak power in the second sprint recovered in parallel with PCr and was still below the first sprint's value after 6 minutes of rest.
The participants were young men doing a maximal 30-second sprint, and shorter or less intense efforts empty the store less. The principle carries over to repeated near-maximal work: rest that is too short means each repetition starts with less PCr, and power drops.
Active and passive recovery
Active recovery means continuing to move at low to moderate intensity between efforts, such as easy pedalling or jogging. Passive recovery means stopping.
Moving between efforts keeps blood flowing, but it also uses oxygen that the muscle could otherwise spend on rebuilding PCr. Dupont and colleagues (2004) tested this in 12 men running 15-second efforts separated by 15 seconds of rest. With passive rest, they lasted 962 seconds on average before exhaustion. With active rest at 40% of their VO₂max, the maximum rate at which the body can take up and use oxygen, they lasted 427 seconds. Muscle oxyhaemoglobin, a near-infrared measure of oxygen in the working muscle, fell more slowly during the efforts with passive rest. The authors suggest this allowed more reoxygenation and PCr resynthesis, though the study did not measure PCr.
A 2021 systematic review of 26 randomised trials concluded that passive recovery generally gives better performance during high-intensity interval exercise. The pattern was clearest for repeated sprints, where six of nine studies found faster times with passive recovery. It was weaker for power output, where four of 17 studies reported an advantage for passive rest. These are single-session results, and most protocols used short, hard efforts.
Rest length for longer intervals
Longer efforts, of three to five minutes, depend mainly on aerobic metabolism, and the trade-off changes. Seiler and Hetlelid (2005) had nine well-trained male runners, with an average VO₂max of 71 ml/kg/min, run six 4-minute intervals as fast as they could sustain, with 1, 2 or 4 minutes of rest.
| Rest | Average speed | Oxygen uptake during work | Peak perceived effort |
|---|---|---|---|
| 1 min | 14.4 km/h | 65.1 ml/kg/min | 17.1 |
| 2 min | 14.7 km/h | 66.2 ml/kg/min | 17.7 |
| 4 min | 14.7 km/h | 64.9 ml/kg/min | 16.8 |
Lengthening rest from one to two minutes raised speed slightly. Doubling it again to four minutes added nothing to speed, though peak perceived effort was slightly lower. Peak blood lactate was similar in all three sessions. When the runners chose their own rest, they took about two minutes. The authors proposed that roughly two minutes of active recovery balances recovery in the muscle with keeping oxygen uptake kinetics, the speed at which oxygen use rises at the start of the next effort, quick. These were highly trained runners, and the study cannot show how much rest less fit people need to hold the same quality.
What happens over weeks
Acute performance is not the same as adaptation. A 2024 systematic review of 24 training studies, covering trained and untrained participants aged 14 to 48 over 3 to 15 weeks, found improvements in fitness with both recovery types: 11 of 13 studies using passive recovery and 9 of 11 using active recovery reported gains. The authors concluded that the recovery type "seems not to affect the outcomes". They did not pool the results statistically, and only two studies involved young people. They suggested that high workloads may call for passive recovery, while lower workloads may suit active recovery.
What heart rate shows during rest
Heart rate falls during rest, but it reflects the cardiovascular system, not the PCr store in the working muscle, and the two do not have to recover together. In the 1995 sprint study, PCr and power were still incomplete after six minutes of rest, so a falling number does not confirm that the next sprint will be as powerful as the first.
During 15- to 30-second rests, heart rate changes little, so the clock is the better guide. During longer rests, the number is more informative. On the Pulz8 live TV dashboard, a tile that returns to a lower zone at its usual pace suggests a member is coping with the set; a tile that stays high for longer than usual is a reason to ask how the member feels. Members recover at different rates, so the same tile colour for everyone is not a sensible requirement. Heart-rate recovery as a fitness signal explains how to compare these patterns over time.
Example: setting rest for three formats
This is an illustration for a general gym group, not a prescription.
| Format | Main aim | Rest in this example | Reason |
|---|---|---|---|
| 6 × 20 s all-out on a bike or rower | Repeat high power | 2–3 min, standing or walking slowly | PCr is about two-thirds restored after 1.5 min |
| 10 × 15 s hard / 15 s rest | Accumulate hard work | 15 s, standing still | Passive rest extended time to exhaustion |
| 6 × 4 min hard | Sustained aerobic work | About 2 min, easy movement | Longer rest gave no extra speed in trained runners |
The rest decision also changes session length. Six 4-minute intervals with 2-minute rests take 24 minutes of work plus 10 minutes of rest across five gaps, 34 minutes in total. With 4-minute rests, the same work takes 44 minutes, ten minutes longer, for no gain in speed in the Seiler study. For short sprints the arithmetic runs the other way: six 20-second sprints with 3-minute rests contain only 2 minutes of work in a 17-minute block, which is the price of keeping each sprint near maximal.
Key points
- Set rest by the aim of the interval, not by habit or the class timer.
- Give short all-out efforts long rest, two minutes or more, and let members stand or walk slowly.
- Keep rests passive in short on/off formats when the goal is to complete more hard repetitions.
- Use about two minutes of easy movement for intervals of several minutes, and allow less fit members more.
- Read heart rate as a cardiovascular cue during longer rests, and rely on the clock for short ones.
- Choose the recovery type that fits the session, since both appear to produce similar gains over weeks.
Sources
- Bogdanis GC, Nevill ME, Boobis LH, Lakomy HK, Nevill AM. Recovery of power output and muscle metabolites following 30 s of maximal sprint cycling in man. Journal of Physiology, 1995.
- Dupont G, Moalla W, Guinhouya C, Ahmaidi S, Berthoin S. Passive versus active recovery during high-intensity intermittent exercises. Medicine & Science in Sports & Exercise, 2004.
- Perrier-Melo RJ, D'Amorim I, Meireles Santos T, Caldas Costa E, Rodrigues Barbosa R, da Cunha Costa M. Effect of active versus passive recovery on performance-related outcome during high-intensity interval exercise. Journal of Sports Medicine and Physical Fitness, 2021.
- Seiler S, Hetlelid KJ. The impact of rest duration on work intensity and RPE during interval training. Medicine & Science in Sports & Exercise, 2005.
- Zouhal H, Ben Abderrahman A, Jayavel A, et al. Effects of passive or active recovery regimes applied during long-term interval training on physical fitness in healthy trained and untrained individuals: a systematic review. Sports Medicine – Open, 2024.
Heart rate is a training signal, not medical advice. If you have a heart condition, or feel chest pain, dizziness or unusual breathlessness during intervals, stop and speak to a doctor before continuing.