How a running session is written
The anatomy of a session: steps, target, intensity, repetitions and recovery. The rules that decide how long an interval lasts and how much you rest, and how to read the notation you will find in any plan.
Every running session, however complicated it looks, is a sequence of steps. Each step answers four questions: what shape it takes, how long it lasts, at what intensity, and what recovery follows. Learn to read that and you can write any session, and understand any plan.
The anatomy of a step
- Function
- Warm-up, work, recovery or cool-down
- Target
- A distance, a time, or open
- Intensity
- % of vVO₂max, pace, zone, heart rate or perceived effort
- Repetitions
- How many times the step is done
- Recovery
- What goes between repetitions
It structures the reading and, above all, stops anyone skipping the warm-up before hard work.
Distance for track and measurable intervals; time for easy runs and for terrain where pace means nothing.
Each yardstick is good for something different. See below.
10 × 400 is ten repetitions of the same step, not ten different steps.
Time or distance, jogging, walking or standing. It is not filler: it decides the stimulus.
With that, “10 × 400 m at 105% of vVO₂max with 200 m jog recovery” is a single step with ten repetitions. And a pyramid (400-800-1200-800-400) is five consecutive steps of one repetition each. Nothing more complicated is needed.
What to measure intensity with
| Yardstick | When to use it | Its problem |
|---|---|---|
| % of vVO₂max | To write a plan that works for any runner | Needs a measured, recent vVO₂max |
| Pace (min/km) | To prepare a specific result: rehearsing target pace | Does not adapt to heat, wind or fatigue |
| Zone | For easy runs and for beginners | Low resolution: very different sessions fit in one zone |
| Heart rate | For long easy runs and hot days | It lags: useless for intervals under 2 minutes |
| Perceived effort (RPE) | Trails, treadmills without data, odd days | Subjective, but surprisingly reliable with practice |
The combination that works
Write the plan in % of vVO₂max — that way it still holds when your fitness changes — and run it watching the pace it translates to, correcting by feel when the day is not there. Heart rate for the long easy runs.
How long an interval lasts
This is the decision people get wrong most often. The length depends on the zone:
| Type | Intensity | Length per repetition | Total work |
|---|---|---|---|
| Short intervals (30/30) | 100–105% vVO₂max | 15 s – 1 min | 10–20 min |
| Long VO₂max intervals | 92–100% vVO₂max | 3–5 min | 15–25 min |
| Threshold intervals | 84–92% vVO₂max | 8–20 min | 20–40 min |
| Continuous tempo | 85–90% vVO₂max | A single block | 20–40 min |
| Strides / accelerations | 110–120% vVO₂max | 10–20 s | 2–3 min |
Short intervals allow more time to be accumulated near VO₂max
Billat’s work on intermittent runs at the velocity of VO₂max showed that a format of 30 seconds of work and 30 of active recovery keeps you near maximal uptake far longer than a continuous effort at severe intensity, because the pause is too short for uptake to drop. That is where the classic 30/30 comes from.
The classic mistake
Programming 5–6 minute repetitions at 100% of vVO₂max. If your time limit is 6 minutes, the first rep leaves you cooked and you run the next four at 90% believing you are at 100%. No repetition should exceed three quarters of your time limit.
How much recovery
Recovery is not rest: it is part of the stimulus. It changes what the session trains, not just how manageable it is.
- Short and equal to the work (1:1 or less): oxygen uptake does not fall between repetitions. That is what you want for VO₂max.
- Long (2:1 or more): uptake drops and every repetition starts from zero. It stops being aerobic work and becomes speed work. Legitimate, but it is a different session.
- Jogging keeps the heart rate high; walking or standing lets it fall much further. With the same pause length, they are two different stimuli.
- At threshold, keep it short: 1–2 minutes between 10-minute blocks. The point is accumulating minutes at pace, not resting.
The variables of an interval can be manipulated separately, and each changes the stimulus
Buchheit and Laursen describe interval training as a problem of nine independent variables — work intensity and duration, pause intensity and duration, number of repetitions and of sets, and the recovery between sets — each with distinct effects on cardiovascular, metabolic and neuromuscular load. There is no generic “interval”: there are decisions.
How the week is arranged
A session is not judged alone, it is judged inside the week. Two rules that avoid most disasters:
- 1
At most two quality sessions per week
Three are sustainable only for runners with years of base and decent volume. Everything else in the week, genuinely easy (plan your running week).
- 2
Never two hard days in a row
Between one VO₂max session and the next, 48–72 hours. Between one tempo and another, 48 is enough. Adaptation happens in the recovery, not in the session.
- 3
The long run counts as quality if it has pace in it
An easy long run is volume. A long run with 3 × 10 min at marathon pace is a hard session: do not put it the day after intervals.
Comparing different sessions
To know whether a week is too much, counting kilometres is not enough: 10 km of intervals is not 10 km of easy running. A simple way to compare is to weight the minutes per zone — ×1 in Z1–Z2, ×2 in Z3–Z4, ×3 in Z5–Z6 — and add them up. It is what the app calls the session “load”.
Reading the notation in any plan
| What it says | What it means |
|---|---|
| 10 × 400 / 200 | Ten repetitions of 400 m with 200 m of jog recovery |
| 4 × 10′ r2′ | Four 10-minute blocks with 2 minutes of recovery |
| 30/30 × 12 | Twelve times 30 seconds hard and 30 easy |
| 3 × (4 × 200) r1′ / R3′ | Three sets of four 200 m repetitions; 1 min between reps, 3 min between sets |
| 20′ CR + 6 strides | Twenty minutes of continuous running and six short accelerations at the end |
| 8 × 45″ hill 6% | Eight 45-second repetitions on a 6% climb, jogging back down |
Three sessions written out in full
- 1
Threshold intervals (vVO₂max 16 km/h)
15 min at 60–68% (5:30–6:10/km) · 4 × 10 min at 86–90% (4:10–4:22/km) with 2 min jogging · 10 min at 55–65% (5:45–6:50/km). Total: around 75 minutes, 40 of them at pace. It is the session that transfers most to 10K and the half.
- 2
Short 30/30 intervals (vVO₂max 16 km/h)
20 min easy · 12 × 30 s at 100–105% (3:34–3:45/km) with 30 s jogging · 10 min easy. Only 6 minutes of hard work, but nearly all of it near maximal uptake. It costs less than it looks and you recover fast.
- 3
Hills (vVO₂max 16 km/h)
15 min easy · 8 × 45 s at 100–110% on a 6% climb, jogging back down very easy (90 s) · 10 min easy. The climb shortens the stride: the same aerobic stimulus as the track with far less impact. Running down fast is what wrecks quads, so you jog down.
Takeaways
- A session is a sequence of steps: function, target, intensity, repetitions and recovery.
- Write the plan in % of vVO₂max and run it watching the translated pace.
- No VO₂max repetition should exceed three quarters of your time limit.
- Recovery decides the stimulus: short for VO₂max, long for speed.
- Two quality sessions a week, never back to back.
- To compare weeks, weight the minutes per zone instead of counting kilometres.
Sources for this chapter
- [1]Billat V, Slawinski J, Bocquet V, et al. (2001). 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. trial
- [2]Buchheit M, Laursen PB (2013). High-intensity interval training, solutions to the programming puzzle: Part I — cardiopulmonary emphasis. Sports Medicine. review