10 × 400m
Source: own Strava export
Ten 400m reps formed a VO2 interval session. The preceding progression and recovery made the set a controlled-speed transition rather than an isolated sprint block. The first three reps met a cross headwind; the turn then gave the remaining reps a tailwind.
The opening fade was erased after the turn, with 1:16, 1:18, 1:17 and 1:16 through reps four to seven before 1:20, 1:19 and 1:21 to close. Heart rate reached 176 by rep five and 177 on the final rep, while the set stayed controlled without a late pace collapse.
Rep splits
| Rep | Time | Pace | HR | Float |
|---|---|---|---|---|
| 1 | 1:19 | 3:17/km | 169 | 1:00 |
| 2 | 1:20 | 3:20/km | 174 | 1:00 |
| 3 | 1:22 | 3:25/km | 171 | 1:00 |
| 4 | 1:16 | 3:09/km | 170 | 1:00 |
| 5 | 1:18 | 3:14/km | 176 | 1:00 |
| 6 | 1:17 | 3:13/km | 174 | 1:00 |
| 7 | 1:16 | 3:11/km | 176 | 1:00 |
| 8 | 1:20 | 3:19/km | 172 | 1:00 |
| 9 | 1:19 | 3:19/km | 176 | 1:00 |
| 10 | 1:21 | 3:23/km | 177 | 1:00 |
What the engine saw
- 10 work intervals detected from lap markers, confirmed by clear pace separation.
- Recoveries average 60s.
Calibration flags
- Running power threshold estimated from the athlete's half-marathon best efforts (60-min power 476 W, 95% of 20-min power 460 W). Treat power zones and load as ±3%.
- Zones and running threshold are one snapshot, read 2 Jul 2026 and applied to every session in the archive. An older session is scored against today's zones, not the zones the athlete trained with then.
Engine read · editorial decode by Splits
Time in zone
The rep pace re-expressed for flat ground and cool air, the effort, not the clock. The gap between actual and true effort is the day's hidden work: conditions were taxing the clock.