Running guides

What is interval training for runners, and does it work?

Interval training alternates hard efforts with recovery. In a meta-analysis, high-intensity intervals improved running economy more than moderate continuous running, but the VO2max effect in well-trained runners is unclear.

By RunFast · Updated 24 October 2026 · 9 min read

In interval training, running workouts alternate hard repeats, called reps, with easier recovery between them. Is interval training good for running? For interval training running workouts, the answer depends on what you measure. In a meta-analysis of randomised trials in endurance runners, high-intensity interval training (HIIT) improved running economy, how much energy a given pace costs, more than moderate continuous running did.¹ In the same review, moderate continuous running had the larger effect on VO2max (maximal oxygen uptake).¹

For well-trained runners, a systematic review of seven studies found that six reported VO2max improvements that were not statistically significant, and called the effect of interval training on VO2max equivocal.² These reviews studied endurance runners and well-trained runners, not specifically recreational runners or beginners.^{1, 2} So treat intervals as one useful kind of hard session, not a proven shortcut: take the pace from a recent race, keep each rep short enough to repeat at the same pace, recover well between reps, and keep most of your running easy.

What interval training is

An interval session has four parts: an easy warm-up, a set of reps at a hard but repeatable effort, a recovery between each rep (an easy jog or a walk), and an easy cool-down. The reps are measured in distance (800 m, for example) or in time (4 min). What makes it an interval session rather than a tempo run is the break: you run hard, recover, and run hard again, instead of holding one steady effort. The guide to what a tempo run is covers the steady kind.

Does interval training work?

The research compares interval training with other training in endurance runners and athletes, and the answer changes with the outcome measured.

Running economy

In a meta-analysis of randomised controlled trials in endurance runners, HIIT improved running economy more than moderate-intensity continuous training, with a standardised mean difference of 0.44.¹ The abstract doesn’t say how trained those runners were, so it isn’t clear how well the result carries over to recreational runners.

VO2max

The same meta-analysis found the opposite for VO2max: moderate continuous training had the greater effect, with a mean difference of 2.48.¹ A systematic review of interval training in well-trained distance runners included seven studies.² Six of them reported VO2max improvements that were not statistically significant.² The authors concluded that the efficacy of interval training to improve VO2max in well-trained runners remains equivocal.²

So the evidence does not support the common claim that high intensity interval training for running reliably raises VO2max, and it says little about interval training for running speed in recreational runners.

Intervals within a whole training mix

If you run intervals as one part of a training week, the studies of training intensity distribution, how training time is split between easy, moderate and hard running, matter too. A 2025 network meta-analysis of 13 studies of 348 endurance athletes, recreational and competitive, found no statistically significant difference between polarised training and any other distribution.³ In a 2026 network meta-analysis of endurance athletes, high-intensity interval training was ranked most likely to optimise time-trial performance, but that is a probability ranking, not a definite effect.⁴ The same analysis found that, compared with polarised training, no other distribution showed a definite advantage for VO2max or time-trial performance.⁴

In practice, intervals fit as a hard day in a mostly easy week. The guide to how much of your running should be easy covers that split, and tempo runs are the other common hard session.

Sprint intervals or high-intensity intervals?

Sprint interval training (SIT) is a separate format from HIIT, and one review compared the two. In a meta-analysis of 12 trials with 460 people, HIIT outperformed SIT for improving VO2max; the abstract does not say the participants were runners.⁵ Most of its outcomes were rated as low or very low quality evidence.⁵ So the finding is a weak one, and it may not carry over to runners.

What it does to your stride

A systematic review of nine studies in endurance runners found increases in stride frequency, contact time and vertical displacement of the centre of mass with interval training, though only two of the studies measured them during the reps themselves.⁶ For short reps of 200–1000 m, the authors suggested long recovery periods of 2–3 min to avoid the increase in stride frequency.⁶ For longer reps, over 1000 m, they suggested that a short recovery of 1–2 min does not cause a high level of muscle fatigue or changes in gait.⁶ That is their guidance, not a trial of recovery length or of performance. They also found no consensus about the acute effects of interval training on running kinematics.⁶

How to apply it

To run an interval session, warm up with easy running, run each rep at the same hard pace, recover fully between reps, and cool down easy. Stop the set when you can no longer hold the pace.

Pace. Take your interval pace from a recent race result rather than from feel alone, for example with the Interval row of the pace calculator. The 5K pace chart and 10K pace chart show race paces for a range of finish times. If your last reps are much slower than your first, slow the pace or lengthen the recoveries next time.

How many and how long. No study here sets a session for recreational runners. One meta-analysis of high-intensity and sprint intervals suggests that athletes and coaches may use 3–6 intervals of 4–5 min at 80–95% of maximal aerobic velocity (MAV), 2–3 sessions per week.⁵ That is a suggestion from mostly low or very low quality evidence, in trials not described as runners, not a tested prescription, and MAV is not the same as the interval pace a calculator gives you.

Recovery. For reps of 200–1000 m, one review suggests 2–3 min of recovery to avoid a change in stride frequency.⁶ For reps over 1000 m, it suggests a short recovery of 1–2 min is enough.⁶ The review groups reps by distance, not time, so check how far your reps are; the rep lengths in the table below, 600–1000 m, are in the shorter group. If you’re unsure, recover longer rather than shorter, so each rep can be run at the same pace.

By goal distance. If you’re doing interval training for a 5K or a 10K, no study here sets the rep length. As one example of an interval training plan, RunFast’s plans use the rep lengths below, with a recovery jog of half the rep distance. These are the app’s method choices, not findings of the reviews above.

Interval rep lengths and recoveries in RunFast's plans, by goal distance
Goal	Rep length	Recovery jog
5K	600 m	300 m
10K	800 m	400 m
Half marathon or marathon	1000 m	500 m
Other goals	800 m	400 m

In RunFast

In RunFast’s plans, a quality session is either a tempo run or an interval session, and an interval session is labelled “VO₂max • speed”. Interval pace is a single pace, not a range, worked out with Daniels’ VDOT model from a recent race or your fitness level: a 10K in 50:00, for example, gives VDOT 40 and an interval pace of about 4:40 /km (about 7:31 /mile). The hard part of the session is 11% of the week’s planned distance, kept between 2.4 and 6 km, cut to 60% in a recovery week, and divided into 4–10 reps of the length in the table above. Each session has 1.5 km of easy running before and after: a 50 km week for a 10K, for example, gives 7 × 800 m with 0.4 km jog recoveries. A week has none to two quality sessions, by phase, level and running days: fewer than three running days a week gives none, three gives at most one, and so does a recovery week. With two, one is a tempo and one is intervals. With one, the taper’s is intervals and the peak phase’s is intervals for 5K and 10K goals; in the build phase it alternates with a tempo by week for 5K and 10K goals, and for other goals it is intervals one week in three. The plan keeps most running easy, and it schedules no sprint-interval sessions. These rules are the plan’s method, not results from the studies in this guide.

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For how intervals sit in a full plan, see the 5K training plan and the 10K training plan. Strength training for runners covers the work that goes alongside your running.

Where the evidence is thin or mixed

Whether HIIT beats moderate continuous running depends on the outcome: in one meta-analysis of endurance runners, HIIT did better for running economy and moderate continuous training did better for VO2max.¹ In well-trained runners, the effect of interval training on VO2max remains equivocal.² The comparison of high-intensity and sprint intervals rests mostly on low or very low quality evidence.⁵

None of the reviews here was of beginners: they studied endurance runners, well-trained runners, endurance athletes, or trials of endurance performance that were not clearly of runners.^{1, 2, 3, 4, 5} The one suggested dose, including 2–3 sessions per week, comes from trials not described as runners and from mostly low or very low quality evidence.⁵ We found no study that sets how often recreational runners or beginners should do intervals, their best rep length or rest ratio, or how a beginner should progress, and no research here on intervals and injury risk or weight loss. In practice, intervals are a reasonable hard session to include, but the research doesn’t show a single best way to do them.

Common questions

Interval training or tempo runs?

In a 2026 network meta-analysis of endurance athletes, high-intensity interval training ranked most likely to be best for time-trial performance and lactate-threshold training for VO2max, but these are probability rankings, not definite effects, and compared with polarised training no other model showed a definite advantage.⁴ Neither has been shown to be better, so you needn’t choose: both can be hard days in a mostly easy week. The guide to tempo runs covers the other session.

Are sprint intervals better than high-intensity intervals?

Not for VO2max, in the one meta-analysis we found: HIIT outperformed sprint interval training, in trials that were not clearly of runners.⁵ Most of that evidence was rated low or very low quality, so the answer is uncertain.⁵

How long should I recover between reps?

One review in endurance runners suggests 2–3 min for reps of 200–1000 m, to avoid an increase in stride frequency, and 1–2 min for reps over 1000 m, though that is guidance rather than a tested result.⁶ The same review found no consensus about the acute effects of interval training on running form.⁶ Recover long enough to run the next rep at the same pace.

How often should I do intervals?

One meta-analysis suggests that athletes and coaches may use 2–3 interval sessions per week.⁵ Its trials were not described as runners, most of its outcomes were rated low or very low quality, and the figure is a suggestion, not a tested prescription.⁵ We found no study that sets a frequency for recreational runners or beginners. Make intervals one of your hard days, keep the rest of the week easy, as in 80/20 running, and give yourself an easy day after a hard session.

This guide is general information, not medical advice. If you have an injury, a health condition or are pregnant, ask a doctor or physiotherapist before changing how you train or eat.

Sources

Feng Y, Li D, Liu Y, Tang D. High-Intensity Interval Training and Moderate-Intensity Continuous Training Affect Running Economy in Endurance Runners: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Journal of Human Kinetics. 2026. doi:10.5114/jhk/205427
Parmar A, Jones TW, Hayes PR. The dose-response relationship between interval-training and VO2max in well-trained endurance runners: A systematic review. Journal of Sports Sciences. 2021. doi:10.1080/02640414.2021.1876313
Rosenblat MA, Watt JA, Arnold JI, Treff G, Sandbakk ØB, Esteve-Lanao J, Festa L, Filipas L, Galloway SD, Muñoz I, Ramos-Campo DJ, Schneeweiss P, Sellés-Pérez S, Stöggl T, Talsnes RK, Zinner C, Seiler S. Which Training Intensity Distribution Intervention will Produce the Greatest Improvements in Maximal Oxygen Uptake and Time-Trial Performance in Endurance Athletes? A Systematic Review and Network Meta-analysis of Individual Participant Data. Sports Medicine. 2025. doi:10.1007/s40279-024-02149-3
Li H, Yang Q, Wang B. Effects of Different Training-Intensity Distribution Models on Maximal Oxygen Uptake and Time-Trial Performance in Endurance Athletes: A Bayesian Network Meta-Analysis. Journal of Strength and Conditioning Research. 2026. doi:10.1519/jsc.0000000000005415
Xiao Y, Li J, Deng Z, Gao W. Effects of High-Intensity Interval Training Versus Sprint Interval Training on Factors Related to Endurance Performance: A Systematic Review and Meta-Analysis. Journal of Strength and Conditioning Research. 2026. doi:10.1519/jsc.0000000000005374
Rodríguez-Barbero S, González-Mohíno F, Rodrigo-Carranza V, Santos-Garcia DJ, Boullosa D, González-Ravé JM. Acute effects of interval training on running kinematics in runners: A systematic review. Gait & Posture. 2023. doi:10.1016/j.gaitpost.2023.04.009