Interval training for runners: what's an interval workout, types and how often

What's an interval workout? A run built from repeats: a hard rep, a planned recovery, another hard rep, until the session is done. That's it. The track sessions, the "6 × 800 m", the 4 × 4 minutes that half the internet swears by, all of them are the same idea with different numbers.

Interval training for runners is popular because it works and because it feels like training. That second part is the problem: plenty of people do intervals three times a week and wonder why they're tired, not faster. This guide covers the main types of intervals, sample sessions by level, how hard to run them, and how often, whether you write the plan yourself or use an app that plans your runs and your lifts.

What's an interval workout?

An interval workout has four parts you can change: how long each rep is, how hard you run it, how long you recover, and how many reps you do. Change any one and you get a different session with a different job.

Compare that with a tempo run, which is continuous, or a fartlek, which mixes surges into a run with no set structure. Intervals are the most precise of the three. You know exactly what you're running and exactly when you get to stop. If the differences blur together, the fartlek run guide puts fartlek, tempo and intervals side by side.

Intervals show up in almost every serious plan, from a first 5K build to a half marathon training plan. What changes from plan to plan is the type and the dose.

Types of interval training for runners

There are four common types. They overlap at the edges, but each has a main job.

The zone and RPE numbers follow the five-zone model we use across this blog. If you need the full map, our HR zones guide has it.

VO2 max intervals

These are the classic "intervals" most people mean. In Helgerud et al. (2007), moderately trained men ran 4 × 4 minutes at 90–95% of max heart rate with 3-minute active recoveries, three days a week for eight weeks. That group improved VO2 max more than groups doing the same total work at lactate threshold (85% of max) or as long slow distance (70% of max).

Why reps of a few minutes? A review of interval programming by Buchheit and Laursen (2013) describes the target as spending at least several minutes per session at or above 90% of VO2 max. Short reps don't get you there before they end. Very long reps can't be held that hard. Two to five minutes is the sweet spot most coaches use.

Threshold intervals

Threshold intervals, or cruise intervals, chop a tempo run into pieces: something like 3 × 8 minutes at a hard-but-controlled effort with a short jog between. You get more time at threshold than you could manage in one continuous block, with less fatigue. They're a staple of half marathon and marathon training.

Short speed reps and hills

Short reps of 15 to 60 seconds, with plenty of rest, train speed and form more than fitness. They should feel fast and relaxed, not desperate. Hill repeats do a similar job with more strength and less speed: run up hard, jog or walk down.

Interval workout examples

Every session below starts with 10–15 minutes of easy running, a few drills and a couple of strides, and ends with 10 minutes easy.

Two rules make these work:

• ›Run the first rep slightly too easy. The last rep should be the hardest, not the slowest.
• ›Stop when quality drops. If a rep is clearly slower despite more effort, the workout is over.

How hard should intervals be?

Hard, but repeatable. Most interval sessions should finish with you feeling like you could have done one more rep.

Use the right gauge for the rep length:

• ›Short reps (under about 90 seconds): use pace or effort. Heart rate lags behind, so it's still climbing when the rep ends.
• ›Longer reps (3–5 minutes): heart rate becomes useful by the second half of the rep. Aim for zone 5 by the end, not in the first 30 seconds.
• ›Threshold reps: zone 4 and RPE 7–8 the whole way. You can say a few words, not sentences.

If you want paces to aim for, base them on a recent race or time trial, not on the time you'd like to run. A running pace guide with a calculator turns one result into training paces, and the honest number is the one that makes intervals productive.

How often should you do interval training?

Once a week for most runners. Twice for experienced runners in a build toward a 5K or 10K. Almost never three times.

The reason is the rest of the week. Across descriptive studies of competitive endurance athletes, Seiler (2010) found the typical pattern was about 80% of sessions at low intensity and about 20% dominated by hard work like intervals. In a nine-week trial in well-trained athletes, a polarized program, mostly easy with some high-intensity intervals, improved key endurance markers more than threshold-focused, high-volume or interval-only training (Stöggl and Sperlich, 2014). Those were trained athletes, so take the direction rather than the exact numbers, but the direction is clear: intervals work best as a small part of a mostly easy week.

That means your easy run days need to be genuinely easy, and so does your weekly long run. If you've ever looked up the long run meaning in a plan, it's simple: your longest run of the week, at an easy effort. Intervals sit on top of that base. They don't replace it.

Intervals also aren't magic for everyone. A meta-analysis of 28 studies in healthy adults found both interval training and continuous endurance training clearly improved VO2 max compared with no exercise (Milanović, Sporiš and Weston, 2015). If you're new, plain consistent running will move your fitness a long way before intervals become the limiting factor.

Intervals for distance runners vs short races

The distance you're training for changes the intervals you need.

• ›5K and 10K: more VO2 max work, like 800 m to 1 km repeats or 3–5 minute reps, plus some short speed reps.
• ›Half and full marathon: more threshold intervals, longer reps, shorter recoveries, and VO2 max work in smaller doses.

That shift is the core of interval training for distance runners explained in one line: longer races want longer, more controlled reps. A guide to track workouts for marathon training would add that the track is useful mainly for precision, not for running everything faster.

At the other end, very short, very fast efforts of 10 to 20 seconds with full recovery are their own category. Our guide to sprint training for beginners starts with strides at the end of easy runs before anything harder.

Interval training for runners who also lift

If you lift, intervals count as one of your hard days. Schedule them like one.

• ›Never heavy legs the day before intervals. The day after is usually fine, because the intervals were run fresh.
• ›Run first if you must double up, and leave several hours before lifting.
• ›One interval session a week is enough during a strength-priority block.

Common interval mistakes

• ›Recovering at tempo pace. The recoveries are part of the workout. Jog them slowly, or walk.
• ›Doing intervals on tired legs. Squats yesterday plus 800s today equals bad squats and bad 800s.
• ›Never progressing. Add a rep, lengthen the reps, or shorten the recovery. One change at a time, every week or two.
• ›Making every run an interval session. If everything is hard, nothing is hard enough.

How exrsz plans intervals

exrsz builds a periodized plan from your goal, schedule, level and equipment, choosing the interval type for the phase you're in and the race you're training for. It balances those sessions against your lifting in one plan, adapts each week to how you actually trained, and reshuffles missed sessions so two hard days don't end up back to back.

FAQ

What's an interval workout?

An interval workout is a run made of repeated hard efforts separated by planned recoveries, such as 5 × 3 minutes hard with 2 minutes easy jogging between. The rep length, effort, recovery and number of reps decide what it trains.

How often should runners do interval training?

Once a week suits most runners, and twice is plenty for experienced runners building toward a short race. Keep the rest of the week mostly easy, as most well-trained endurance athletes do (Seiler, 2010).

What is a good interval workout for beginners?

Something like 6 × 1 minute hard with 2 minutes easy jogging between, after a 10–15 minute warm-up. Run the reps at a controlled effort you could repeat, not flat out.

Are intervals better than easy running for VO2 max?

In one eight-week trial, 4 × 4-minute intervals at 90–95% of max heart rate improved VO2 max more than the same total work at threshold or easy intensity (Helgerud et al., 2007). Easy running still builds the base that lets you handle intervals, so you need both.