Intervalsconfidence 0.83
5 × 400m
Colin Dismuke50 km / marathon build
Source: own Strava export
Intervals
5 × 400m
Distance
7.9 km
Moving
35:49
Rep pace
3:21/km
Avg HR
152 bpm
Reps
5
Shape of the sessionEasyWorkFastest
warm up
cool down
0:005 × work / float35:49
The decode
A mixed interval session combined 1km and 400m reps. The longer work demanded sustained pressure before the shorter reps tested speed under accumulated fatigue.
The 1km reps ran at 3:37/km, 3:39/km and 3:34/km before the 400m block tightened to 3:24/km, 3:21/km, 3:24/km, 3:15/km and 3:23/km. The 60-second recoveries remained fixed, and the set held together as heart rate rose from 151 on the first 400m rep to 158 on the final one.
Rep splits
| Rep | Time | Pace | HR | Float |
|---|---|---|---|---|
| 1 | 1:22 | 3:24/km | 151 | 1:00 |
| 2 | 1:20 | 3:21/km | 145 | 1:00 |
| 3 | 1:21 | 3:24/km | 152 | 1:00 |
| 4 | 1:18 | 3:15/km | 153 | 1:00 |
| 5 | 1:21 | 3:23/km | 158 | 1:00 |
0.83
confidence
What the engine saw
- 5 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
Heart rate
Z1
Recovery23%
Z2
Endurance31%
Z3
Tempo25%
Z4
Threshold21%
Z5
VO₂max0%
Pace
Z1
Easy50%
Z2
Endurance1%
Z3
Tempo10%
Z4
Threshold27%
Z5
VO₂max7%
Z6
Speed5%
Power
Z1
Recovery13%
Z2
Endurance23%
Z3
Tempo14%
Z4
Threshold26%
Z5
VO₂max24%
Z6
Anaerobic0%
Z7
Neuro0%
Aerobic decoupling · Pa:HR+2.4%
Effort & efficiency
0.78
Running effectiveness
speed per watt/kg, reps
6.3 w/kg
Power-to-weight
rep average
2.76
Efficiency factor
norm. power per bpm
1.09
Variability index
1.0 = perfectly even power
1.7%
Rep consistency
pace spread across reps, lower is tighter
849 kJ
Total work
mechanical energy
526 kcal
Energy
estimated burn
703 bpk
Cardiac cost
heartbeats per km
21%
Above threshold
≥ 164 bpm (Z4+)
-0:12/km
Split balance
negative split, faster 2nd half
Conditions-adjusted pace18°C · +15 m
Actual
3:21/km
Grade-adjusted
3:21/km
Heat-adjusted
3:19/km
−2s/km
True effort
3:19/km
−2s/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.