Interval training
Evidence: moderate
The finishing stimulus on top of an easy base. It carries most of the injury and overtraining risk, so the dose has to match the individual.
Interval training is repeated hard efforts with recovery between them, used to accumulate time at intensities a runner cannot hold continuously. Its core rationale for VO₂max development is that intermittent efforts at the velocity associated with VO₂max keep an athlete at or near maximal oxygen uptake far longer than a continuous run would (Billat et al. 2000).
Typical prescriptions
- VO₂max intervals. Reps of roughly three to five minutes near the velocity at VO₂max, with work-to-rest near 1:1, to maximise time spent above about 90% of VO₂max (Billat 2001). Longer reps tend to accumulate more time in that zone than very short, intensified ones (Front Sports Act Living 2024).
- The 4×4. Four bouts of four minutes at 90 to 95% of maximum heart rate reliably raise VO₂max in moderately trained people (Helgerud et al. 2007). Transfer to already-elite runners is less clear.
- Threshold work. Sustained or broken efforts at lactate threshold, the basis of double-threshold training.
How much elite runners actually do
Observationally, elite distance runners spend roughly 75 to 80% of training easy and 15 to 25% at or above threshold, typically across two to four threshold sessions and one to two higher-intensity sessions per week (Kelemen et al. 2024). Reduced-volume, higher-intensity formats can still improve trained runners: the 10-20-30 protocol cut volume by over half yet improved 5 km time and raised VO₂max (Gunnarsson & Bangsbo 2012).
Intensity is the finishing stimulus, not the foundation. It sits on top of the easy volume that does the bulk of the work, and its dose has to be matched to the individual, because hard sessions carry most of the injury and overtraining risk.
What the sessions look like
Common interval sessions
- VO₂max: 5 × 3 min, or 6 × 800 m, near the pace you could race for about 10 to 15 minutes, with jog recoveries of roughly equal time. Aim to accumulate 12 to 20 minutes of hard running.
- VO₂max, short: 10 × 400 m at a similar effort, shorter recoveries, for runners who break down on longer reps.
- Threshold: 4 × 8 to 10 min, or 3 × 10 min, at threshold effort with short recoveries, the basis of double-threshold work.
The variables that matter are intensity, rep duration, recovery duration and total volume. For VO₂max development the target is to spend as long as possible above about 90% of VO₂max, which is why moderately long reps with incomplete recovery work better than very short, very fast ones that never let oxygen uptake climb (Billat 2001; Front Sports Act Living 2024).
Common mistakes
The usual ways interval training goes wrong
- Running the reps too fast. The most common error: turning a controlled VO₂max or threshold session into a near-race effort raises the cost without raising the benefit, and wrecks the next few days.
- Recoveries too short to hold quality. If pace collapses across the set, the stimulus is lost; the last rep should resemble the first.
- Intervals on too little base. Hard work on a thin aerobic base is the fast route to injury and overtraining.
- Too many hard days. Elites still keep roughly 75 to 80% of running easy (Kelemen et al. 2024); one or two quality sessions a week is enough for most runners.