Intervals
Yasso 800s
The classic marathon predictor
Main set: 8 × (800 m @ 85% + 3 min @ 40%) · 5 min @ 70%
About this workout
Amby Burfoot of Runner's World named this session after Bart Yasso, who had used it for years: run 800 m reps in the same minutes and seconds as your goal marathon in hours and minutes (3:20 for a 3:20 marathon), jog the same time between reps, and build from 4 reps to 10 over the weeks before the race. The claim that it predicts your marathon time is anecdotal; it holds for some runners and not for others.
Fartlek's version runs 8 × 800 m at 85% with a fixed 3-minute jog and a 5-minute steady finish, so it trains the same engine without being the prediction test. A coach's take on Yasso 800s.
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 |
| Yasso 800s | 8 × (800 m @ 85% + 3 min @ 40%) | Strong 800, easy 3-minute jog |
| Steady close | 5 min @ 70% | Settle into rhythm |
| 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.
- 60% Steady. Still chatty, breathing deeper.
- 70% Moderately hard. Short sentences only.
- 85% Very hard. A word or two, tops.
Pete's tip
Run each 800 at comfortably hard effort, then jog easy for equal time. Stay smooth and controlled. This builds race-day stamina and mental toughness.
Pete, Fartlek's AI coach
What it trains
Stamina. Maintain intensity over sustained efforts.