Intervals
Billat 30/30s
Classic French VO2max protocol
Main set: 15 × (30 s @ 95% + 30 s @ 50%) · 4 × (15 s @ 85% + 45 s @ 30%)
About this workout
French physiologist Véronique Billat studied this session in 2000: 30 seconds at the speed at which you reach your maximal oxygen uptake (close to your 3000 m race pace), alternated with 30 seconds at half that speed, repeated until you can't hold the pace. In her study, trained runners spent more time at VO2max this way than in a continuous hard run, although it was a single session and runners varied a lot. 30/30 intervals existed before her; her version made the recovery a slow jog.
Fartlek's version runs 15 reps at 95% with 30 seconds easy between them, then adds 4 short pickups. Run the reps at a pace you could hold for about 5 to 6 minutes, not as sprints. The 2000 study.
The workout
| Block | What to run | Cue |
|---|---|---|
| Warm-up | 4 min @ 40% + 2 min @ 50% + 30 s @ 70% + 1 min rest | Easy start, build gradual |
| Billat 30/30s | 15 × (30 s @ 95% + 30 s @ 50%) | Hard 30, float 30 |
| Form strides | 4 × (15 s @ 85% + 45 s @ 30%) | Quick, smooth finish |
| Cool-down | 2 min @ 30% | Ease down, breathe |
How each effort should feel
Efforts are a percentage of your all-out effort, set by feel (RPE), not by pace. From Fartlek's effort guide:
- 30% Very easy. Walking pace or the gentlest jog.
- 40% Easy. Relaxed jog, easy to chat.
- 50% Comfortable. Easy running, full sentences.
- 70% Moderately hard. Short sentences only.
- 85% Very hard. A word or two, tops.
- 95% All out. Nothing left in the tank.
Pete's tip
Run hard 30s near your max, then float easy 30s and never stop moving. This rhythm maximizes time at VO2max. Stay tall, quick turnover.
Pete, Fartlek's AI coach
What it trains
Speed. Improve your pace and explosiveness.