Intervalsconfidence 0.83
20 × 400m
Colin Dismuke50 km / marathon build
Source: own Strava export
Intervals
20 × 400m
Distance
15.9 km
Moving
73:04
Rep pace
3:38/km
Avg HR
166 bpm
Reps
20
Planned vs actual · TrainingPeaksPlanned 14.0 kmRan 1:13:04 · 15.9 kmIF 1.30TSS 204
Shape of the sessionEasyWorkFastest
warm up
cool down
0:0020 × work / float73:04
The decode
This was a threshold set of 20 × 400 m with 30-second static or walking recoveries. The structure targeted consistent work rather than an aggressive opening.
The reps stayed between 1:25 and 1:30, or 3:32-3:44/km. Heart rate rose from 168 on rep 1 to 181 on rep 20, with 166 on rep 11, and the final rep matched the opening rep at 1:25.
Rep splits
| Rep | Time | Pace | HR | Float |
|---|---|---|---|---|
| 1 | 1:25 | 3:32/km | 168 | 0:30 |
| 2 | 1:29 | 3:42/km | 169 | 0:30 |
| 3 | 1:27 | 3:36/km | 171 | 0:30 |
| 4 | 1:27 | 3:37/km | 171 | 0:30 |
| 5 | 1:27 | 3:37/km | 173 | 0:30 |
| 6 | 1:27 | 3:38/km | 173 | 0:30 |
| 7 | 1:27 | 3:37/km | 175 | 0:30 |
| 8 | 1:27 | 3:37/km | 176 | 0:30 |
| 9 | 1:26 | 3:36/km | 177 | 0:30 |
| 10 | 1:30 | 3:44/km | 176 | 0:30 |
| 11 | 1:28 | 3:41/km | 166 | 0:30 |
| 12 | 1:26 | 3:35/km | 174 | 0:30 |
| 13 | 1:27 | 3:38/km | 177 | 0:30 |
| 14 | 1:27 | 3:38/km | 177 | 0:30 |
| 15 | 1:27 | 3:37/km | 179 | 0:30 |
| 16 | 1:26 | 3:35/km | 180 | 0:30 |
| 17 | 1:29 | 3:42/km | 180 | 0:30 |
| 18 | 1:27 | 3:37/km | 180 | 0:30 |
| 19 | 1:28 | 3:39/km | 181 | 0:30 |
| 20 | 1:25 | 3:33/km | 181 | 0:30 |
0.83
confidence
What the engine saw
- 20 work intervals detected from lap markers, confirmed by clear pace separation.
- Recoveries average 30s.
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
Recovery8%
Z2
Endurance18%
Z3
Tempo6%
Z4
Threshold31%
Z5
VO₂max36%
Pace
Z1
Easy55%
Z2
Endurance7%
Z3
Tempo13%
Z4
Threshold23%
Z5
VO₂max2%
Z6
Speed0%
Power
Z1
Recovery12%
Z2
Endurance19%
Z3
Tempo28%
Z4
Threshold29%
Z5
VO₂max13%
Z6
Anaerobic0%
Z7
Neuro0%
Aerobic decoupling · Pa:HR+7.9%
Effort & efficiency
0.80
Running effectiveness
speed per watt/kg, reps
5.7 w/kg
Power-to-weight
rep average
2.51
Efficiency factor
norm. power per bpm
1.10
Variability index
1.0 = perfectly even power
1.4%
Rep consistency
pace spread across reps, lower is tighter
1844 kJ
Total work
mechanical energy
1214 kcal
Energy
estimated burn
847 bpk
Cardiac cost
heartbeats per km
67%
Above threshold
≥ 164 bpm (Z4+)
-0:04/km
Split balance
negative split, faster 2nd half
Conditions-adjusted pace35°C · +63 m
Actual
3:37/km
Grade-adjusted
3:37/km
Heat-adjusted
3:21/km
−16s/km
True effort
3:21/km
−16s/km
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.