Intervals
Deek's Quarters
De Castella's continuous grass 400s
Main set: 8 × (400 m @ 85% + 200 m @ 50%)
About this workout
Rob de Castella, the 1983 world marathon champion, ran this session every week with coach Pat Clohessy: 8 × 400 m at around 3K to 5K pace, each followed by a brisk 200 m float, run continuously for about 3 miles (about 5 km). Because the float stays quick, it is threshold running dressed up as intervals.
Fartlek's version has the same structure, 8 × 400 m at 85% with 200 m at a comfortable pace; keep the floats brisk rather than jogging them. More on Deek's Quarters.
The workout
| Block | What to run | Cue |
|---|---|---|
| Warm-up | 5 min @ 30% + 3 min @ 40% + 3 × (20 s @ 60% + 40 s @ 30%) + 1 min rest | Easy flow, gentle build; three short pickups, float between, then settle |
| Quarters | 8 × (400 m @ 85% + 200 m @ 50%) | 400 hard, 200 float |
| Cool-down | 6 min @ 30% | Easy jog, breathe deep |
Times for distance reps assume a 6:00/km pace.
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.
- 60% Steady. Still chatty, breathing deeper.
- 85% Very hard. A word or two, tops.
Pete's tip
Roll through the 400s at a strong, even effort and float the 200s without stopping. Keep it honest: no heroics early, no fade late.
Pete, Fartlek's AI coach
What it trains
Stamina. Maintain intensity over sustained efforts.