Session types: easy runs, tempo, intervals, fartlek, hills and the long run
The full catalogue of running sessions, what adaptation each one targets, how it is prescribed, and how many fit in a week without piling up fatigue.
Nearly all distance training is built from seven session types. They differ in duration, intensity and structure, but each exists to provoke a specific adaptation. Knowing which is which is what separates “going for a run” from training.
| Session | Intensity | Typical prescription | What it trains |
|---|---|---|---|
| Easy run | Z1 | 30–60 min while talking | Aerobic base, capillarisation, recovery |
| Long run | Z1 (with Z2 sections) | 75–150 min or 25–35% of weekly volume | Durability, fat use, mental resilience |
| Tempo / threshold | Z2 | 20–40 min continuous or 3×10 min | Holding pace for longer |
| Long intervals (VO₂max) | Z3 | 4–6 × 3–5 min, 2–3 min recovery | Aerobic power |
| Short intervals | Z3+ | 10–20 × 400 m or 30–60 s | Specific speed, tolerance |
| Fartlek | Mixed | 40 min alternating 1–3 min hard / easy | Pace changes, versatility |
| Hills | Z3 by effort | 8–12 × 45–60 s uphill | Specific strength, economy |
The easy run: 70–80% of what you do
It is the most important session and the worst executed. Its goal is not to tire you: it is to accumulate aerobic volume at a low recovery cost, so the hard sessions can actually be hard. If your easy runs leave you beaten up, your intervals will not be intervals.
Rule of thumb
A well-executed easy run is one you finish feeling you could repeat it tomorrow. If in doubt, go easier: running your easy runs too fast is the most expensive mistake in recreational running.
Tempo: the work that pays the amateur most
Running 20–40 minutes just below or around threshold is the session that transfers most to 10K, half and full marathon. It can be continuous (25–35 min) or broken into blocks (3–4 × 10 min with 2 min easy), which is more manageable and lets you accumulate more time at pace.
Intervals: when and how many
For VO₂max, long intervals pay off more than short ones
A meta-analysis of randomised controlled trials found significantly larger effects on VO₂max with intervals of ≥2 minutes, ≥15 accumulated minutes of hard work and programs of 4 to 12 weeks. Intervals of 3–5 minutes (1,000–1,200 m) are, in practice, the format with the best stimulus-to-fatigue ratio.
- One hard session for every 3–4 easy ones. Two a week is the reasonable ceiling for most people; three only with years of base.
- Warm up for 15 minutes and include 3–4 twenty-second accelerations before the first rep.
- Recoveries are part of the session: shorten them and you change the stimulus (and not always for the better).
- Finish able to do one more rep. Emptying the tank in training buys fatigue, not adaptation.
Hills and fartlek: intensity without the beating
Short hills let you reach high intensities with less impact velocity and more force demand: useful when first introducing quality, in pre-season, and for runners prone to niggles. Fartlek, being independent of the watch, is how you get intensity in when the terrain or your head will not support a structured session.
The long run
As a common reference, between 25% and 35% of weekly volume. Its duration matters more than its distance: beyond 2–2.5 hours the recovery cost grows much faster than the benefit, and for the marathon it is better to add blocks at target pace inside the long run than to keep extending it.
How to build the week with this
- Most sessions: easy, conversational running.
- One weekly tempo session as the backbone of performance.
- One interval session once the base is there; 3–5 min reps by default.
- One long run, between 25 and 35% of weekly volume.
- Hills and fartlek to add intensity without the technical demands of the track.
Sources for this chapter
- [1]Wen D, Utesch T, Wu J, et al. (2019). Effects of different protocols of high intensity interval training for VO2max improvements in adults: A meta-analysis of randomised controlled trials. Journal of Science and Medicine in Sport. meta-analysis
- [2]Seiler S (2010). What is best practice for training intensity and duration distribution in endurance athletes?. International Journal of Sports Physiology and Performance. review