How to structure interval running workouts

Interval running workouts alternate hard efforts with planned recoveries, so you spend more time at a high intensity than you could in one continuous run. A well-built session is not just “run fast, then rest”: the length of each rep, its pace, the recovery and the number of reps all change what you train.

In one lab study, eight trained runners alternated 30 seconds at the speed that elicits their maximal oxygen uptake (vVO2max) with 30 seconds at half that speed. They stayed at VO2max for almost 8 minutes on average, against under 3 minutes in a hard continuous run. Breaking the effort up lets you accumulate more quality work.

The anatomy of an interval session

Every session has the same four parts, whatever the goal:

1. Warm-up (15–20 min). Easy running, a few drills, then 3–4 relaxed strides of about 20 seconds. Warm-up research suggests starting with your oxygen uptake already raised, but without being tired.
2. The main set. The reps, organized in one or more sets.
3. The recoveries. Easy jogging or walking between reps.
4. Cool-down (10 min). Easy running to bring the effort down before you stop.

The four levers of interval training

Buchheit and Laursen list up to nine variables in an interval prescription. For runners, four levers do most of the work:

• Rep length: from 15–30 seconds to 10 minutes or more.
• Intensity: threshold, VO2max or faster, set by pace, heart rate or effort.
• Recovery: its length and whether you jog, walk or stand.
• Volume: the number of reps and sets, which sets the total time at intensity.

Change one lever and the session changes character. Six 400 m reps with a long recovery are a speed session; the same reps with a 30-second recovery become a hard aerobic session.

Families of sessions, and what each one trains

Short intervals (30/30)

The 30/30 format studied by Véronique Billat alternates 30 seconds at 100% of vVO2max and 30 seconds at 50%. Each rep is short, which makes it a good first VO2max session. But in a study of triathletes, 60/30 reps kept athletes above 90% of VO2max far longer than 30/30, so short reps are not the whole story.

Long intervals

Reps of about 3 to 5 minutes, close to your 3K–5K race pace, are the classic way to spend several minutes per session near VO2max, the “red zone” Buchheit and Laursen describe as an effective stimulus. In Jack Daniels’ system, these “interval pace” reps usually last 3 to 5 minutes.

Threshold or tempo

Longer reps at a pace you could race for roughly an hour, with short jog breaks. It feels “comfortably hard”: you can say a few words, not hold a conversation. It is the backbone of 10K and half marathon training.

Hill repeats

Uphill reps of 30 to 90 seconds build strength and running economy with less impact than flat speed work. In a six-week study, well-trained runners who added uphill interval sessions improved their 5 km time trial by about 2% on average; the hardest program gave the biggest gain in running economy.

Pyramids (for example 1-2-3-4-3-2-1 minutes, a little faster as the reps get shorter) mix these paces in one session and teach you to change gears.

How to pick your interval paces

Use the most reliable reference you have:

• A recent race. A 5K or 10K from the last couple of months is the best estimate; Daniels’ VDOT tables turn it into threshold and interval paces.
• A field test. A short all-out track test estimates your vVO2max (VMA in France). Short reps sit close to it, longer reps a little below.
• Effort. On a 1–10 scale, threshold feels like 6–7, long intervals 8, short hard reps 8–9. Use effort on hills, trails and hot days, when pace lies.

Heart rate lags behind the effort at the start of each rep, so for short reps pace or effort is the better guide. Run the first rep no faster than the last: if you can’t hold the pace on the final rep, the target was too fast.

How long should recovery be between intervals?

When well-trained runners did six 4-minute reps with 1, 2 or 4 minutes of recovery, going from 1 to 2 minutes made them slightly faster, and 4 minutes added nothing. Left to choose, they rested about 2 minutes on average.

• Long intervals (3–5 min): about 50–100% of the rep time, jogging.
• Threshold reps: short, about 1 minute for every 5 minutes of work.
• Short intervals (30/30): equal to the rep, at an easy jog to keep oxygen uptake high.
• Short fast reps (200–400 m at mile pace): longer, so you can run each one with good form.

How many interval sessions per week?

For most runners, one is enough and two is plenty. Elite endurance athletes do roughly 80% of their sessions at low intensity and about 20% with hard work such as intervals. In recreational runners preparing a 10K, a 10-week program built mostly on easy running improved race times by 5.0%, against 3.6% for one with much more moderate “in-between” running (a difference that was not statistically significant overall).

A meta-analysis adds that less-trained people improved the most (up to about 6% in time trials, against about 2% for trained athletes), and that more interval work beyond a minimal dose did not always bring more gains. Put your interval day between easy days, and keep the long run easy.

A simple 4–6 week progression

Progress the volume before the pace. Start with a session you finish feeling you could do one more rep, then add one rep or a little time each week, with a lighter week every third or fourth week. When the whole session feels controlled, speed up slightly or move to longer reps. A 10K block could go: 5 × 2 min, 6 × 2 min, 5 × 3 min, an easier 4 × 2 min, 6 × 3 min, then 5 × 1,000 m.

Interval running for beginners

Build a few weeks of regular easy running first. Then start with a fartlek-style session: after the warm-up, 8 × 1 minute brisk (about 7 out of 10) with 2 minutes of easy jogging or walking. Once a week is enough. If you have a health condition or haven’t exercised in a long time, check with a health professional before adding hard efforts.

Example sessions for 5K, 10K and half marathon

All of these start with 15–20 minutes of easy running and strides, and end with 10 minutes of easy running.

Common mistakes

• The first rep is the fastest. Even pacing across reps beats a heroic start.
• Recoveries too short. The reps slow down and the session becomes a long tempo run.
• Intervals too often. Hard days back to back leave you tired for both; most of your fitness is built by easy running (see our guide to zone 2 running).
• Skipping the warm-up. The first two reps then serve as the warm-up, at the wrong pace.

FAQ

Sources

1. Billat VL et al., Intermittent runs at the velocity associated with maximal oxygen uptake enables subjects to remain at maximal oxygen uptake for a longer time than intense but submaximal runs, European Journal of Applied Physiology, 2000.
2. Billat LV, Interval training for performance: a scientific and empirical practice. Part I: aerobic interval training, Sports Medicine, 2001.
3. Millet GP et al., VO2 responses to different intermittent runs at velocity associated with VO2max, Canadian Journal of Applied Physiology, 2003.
4. Buchheit M, Laursen PB, High-intensity interval training, solutions to the programming puzzle. Part I: cardiopulmonary emphasis, Sports Medicine, 2013.
5. Seiler S, Hetlelid KJ, The impact of rest duration on work intensity and RPE during interval training, Medicine & Science in Sports & Exercise, 2005.
6. Seiler S, What is best practice for training intensity and duration distribution in endurance athletes?, International Journal of Sports Physiology and Performance, 2010.
7. Muñoz I et al., Does polarized training improve performance in recreational runners?, International Journal of Sports Physiology and Performance, 2014.
8. Barnes KR et al., Effects of different uphill interval-training programs on running economy and performance, International Journal of Sports Physiology and Performance, 2013.
9. Rosenblat MA et al., Programming interval training to optimize time-trial performance: a systematic review and meta-analysis, Sports Medicine, 2021.
10. Bishop D, Warm up II: performance changes following active warm up and how to structure the warm up, Sports Medicine, 2003.
11. Daniels J, Daniels’ Running Formula, 4th edition, Human Kinetics, 2022.