Intervalsconfidence 0.83
12 × 400m
Colin Dismuke50 km / marathon build
Source: own Strava export
Intervals
12 × 400m
Distance
20.4 km
Moving
92:29
Rep pace
3:33/km
Avg HR
157 bpm
Reps
13
Shape of the sessionEasyWorkFastest
warm up
0:0013 × work / float92:29
The decode
Twelve 400m reps with a 12km cool-down made this a speed session embedded in substantial volume. The one-minute recoveries kept the work dense, with the short repetitions demanding pace control before the long aerobic finish.
The set opened at 3:22/km and 3:24/km, then settled around 3:29-3:31/km before slowing to 3:37/km, 3:36/km, 3:38/km and 3:44/km. Heart rate rose from 160 and 164 to 168-174, so the later pace loss came under sustained cardiovascular load rather than a clean reset between reps.
Rep splits
| Rep | Time | Pace | HR | Float |
|---|---|---|---|---|
| 1 | 1:21 | 3:22/km | 160 | 1:00 |
| 2 | 1:22 | 3:24/km | 164 | 1:00 |
| 3 | 1:21 | 3:22/km | 140 | 1:00 |
| 4 | 1:24 | 3:30/km | 168 | 1:00 |
| 5 | 1:24 | 3:31/km | 169 | 1:00 |
| 6 | 1:24 | 3:29/km | 173 | 1:00 |
| 7 | 1:27 | 3:37/km | 172 | 1:00 |
| 8 | 1:26 | 3:36/km | 172 | 1:00 |
| 9 | 1:27 | 3:38/km | 170 | 1:00 |
| 10 | 1:29 | 3:44/km | 173 | 1:00 |
| 11 | 1:27 | 3:36/km | 172 | 1:00 |
| 12 | 1:25 | 3:34/km | 174 | 0:11 |
| 13 | 1:36 | 3:45/km | 176 | — |
0.83
confidence
What the engine saw
- 13 work intervals detected from lap markers, confirmed by clear pace separation.
- Recoveries average 56s.
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
Endurance39%
Z3
Tempo15%
Z4
Threshold21%
Z5
VO₂max17%
Pace
Z1
Easy57%
Z2
Endurance21%
Z3
Tempo12%
Z4
Threshold7%
Z5
VO₂max2%
Z6
Speed0%
Power
Z1
Recovery0%
Z2
Endurance24%
Z3
Tempo43%
Z4
Threshold18%
Z5
VO₂max13%
Z6
Anaerobic1%
Z7
Neuro0%
Aerobic decoupling · Pa:HR+4%
Effort & efficiency
0.75
Running effectiveness
speed per watt/kg, reps
6.3 w/kg
Power-to-weight
rep average
2.58
Efficiency factor
norm. power per bpm
1.04
Variability index
1.0 = perfectly even power
3.4%
Rep consistency
pace spread across reps, lower is tighter
2463 kJ
Total work
mechanical energy
1406 kcal
Energy
estimated burn
801 bpk
Cardiac cost
heartbeats per km
38%
Above threshold
≥ 164 bpm (Z4+)
-0:18/km
Split balance
negative split, faster 2nd half
Conditions-adjusted pace23°C · +69 m
Actual
3:33/km
Grade-adjusted
3:33/km
Heat-adjusted
3:26/km
−7s/km
True effort
3:26/km
−7s/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.