Intervalsconfidence 0.88
10 x 400m
Colin Dismuke50 km / marathon build
Source: own Strava export
Intervals
10 x 400m
Distance
7.8 km
Moving
34:11
Rep pace
3:33/km
Avg HR
166 bpm
Reps
11
Shape of the sessionEasyWorkFastest
warm up
cool down
0:0011 × work / float34:11
The decode
Ten 400m reps with 60s floats formed a speed-endurance set. The active recoveries kept the work continuous and made repeatability the constraint rather than isolated speed.
Pace stayed between 3:22/km and 3:32/km through the first nine reps, then fell to 3:42/km on rep 10. Heart rate reached 176 by rep 9 and the session maximum was 190, with the late slowdown showing that the floats did not fully preserve the final rep.
Rep splits
| Rep | Time | Pace | HR | Float |
|---|---|---|---|---|
| 1 | 1:21 | 3:23/km | 166 | 1:00 |
| 2 | 1:25 | 3:32/km | 165 | 1:00 |
| 3 | 1:23 | 3:27/km | 160 | 1:00 |
| 4 | 1:24 | 3:31/km | 170 | 1:00 |
| 5 | 1:24 | 3:30/km | 163 | 1:00 |
| 6 | 1:21 | 3:23/km | 166 | 1:00 |
| 7 | 1:21 | 3:22/km | 173 | 1:00 |
| 8 | 1:23 | 3:28/km | 175 | 1:00 |
| 9 | 1:25 | 3:33/km | 176 | 1:00 |
| 10 | 1:29 | 3:42/km | 172 | 1:00 |
| 11 | 1:00 | 4:16/km | 175 | — |
0.88
confidence
What the engine saw
- 11 work intervals detected from lap markers, confirmed by clear pace separation.
- Recoveries average 60s.
- Matches the athlete's own session label.
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
Heart rate
Z1
Recovery7%
Z2
Endurance9%
Z3
Tempo11%
Z4
Threshold55%
Z5
VO₂max20%
Pace
Z1
Easy45%
Z2
Endurance4%
Z3
Tempo19%
Z4
Threshold17%
Z5
VO₂max15%
Z6
Speed1%
Power
Z1
Recovery2%
Z2
Endurance35%
Z3
Tempo12%
Z4
Threshold30%
Z5
VO₂max17%
Z6
Anaerobic5%
Z7
Neuro0%
Aerobic decoupling · Pa:HR+4.7%
Effort & efficiency
0.74
Running effectiveness
speed per watt/kg, reps
6.3 w/kg
Power-to-weight
rep average
2.60
Efficiency factor
norm. power per bpm
1.06
Variability index
1.0 = perfectly even power
6.9%
Rep consistency
pace spread across reps, lower is tighter
837 kJ
Total work
mechanical energy
549 kcal
Energy
estimated burn
723 bpk
Cardiac cost
heartbeats per km
74%
Above threshold
≥ 164 bpm (Z4+)
-0:14/km
Split balance
negative split, faster 2nd half
Conditions-adjusted pace16°C · +23 m
Actual
3:32/km
Grade-adjusted
3:32/km
Heat-adjusted
3:32/km
True effort
3:32/km
The rep pace re-expressed for flat ground and cool air, the effort, not the clock. Adjustments are modest on this one; on a hot day or a hilly route this is where the real work hides.