Intervalsconfidence 0.83
4 × 800m
Colin Dismuke50 km / marathon build
Source: own Strava export
Intervals
4 × 800m
Distance
17.6 km
Moving
87:21
Rep pace
3:41/km
Avg HR
152 bpm
Reps
4
Planned vs actual · TrainingPeaksPlanned not setRan 1:27:21 · 17.6 kmIF 1.26TSS 230
Shape of the sessionEasyWorkFastest
warm up
cool down
0:004 × work / float87:21
The decode
The session was a 4 × 800 m interval set around 3:40/km.
The reps ran 3:40/km, 3:41/km, 3:45/km and 3:36/km, with heart rate at 170, 172, 172 and 172. The recoveries between reps were 2:45, 2:43 and 2:59.
Rep splits
| Rep | Time | Pace | HR | Float |
|---|---|---|---|---|
| 1 | 2:56 | 3:40/km | 170 | 2:45 |
| 2 | 2:57 | 3:41/km | 172 | 2:43 |
| 3 | 3:00 | 3:45/km | 172 | 2:59 |
| 4 | 2:53 | 3:36/km | 172 | 5:36 |
0.83
confidence
What the engine saw
- 4 work intervals detected from lap markers, confirmed by clear pace separation.
- Recoveries average 211s.
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
Recovery21%
Z2
Endurance50%
Z3
Tempo13%
Z4
Threshold8%
Z5
VO₂max8%
Pace
Z1
Easy79%
Z2
Endurance9%
Z3
Tempo7%
Z4
Threshold5%
Z5
VO₂max0%
Z6
Speed0%
Power
Z1
Recovery4%
Z2
Endurance50%
Z3
Tempo23%
Z4
Threshold16%
Z5
VO₂max6%
Z6
Anaerobic0%
Z7
Neuro0%
Aerobic decoupling · Pa:HR-0.7%
Effort & efficiency
0.74
Running effectiveness
speed per watt/kg, reps
6.2 w/kg
Power-to-weight
rep average
2.53
Efficiency factor
norm. power per bpm
1.07
Variability index
1.0 = perfectly even power
1.4%
Rep consistency
pace spread across reps, lower is tighter
2121 kJ
Total work
mechanical energy
1275 kcal
Energy
estimated burn
849 bpk
Cardiac cost
heartbeats per km
16%
Above threshold
≥ 164 bpm (Z4+)
-0:28/km
Split balance
negative split, faster 2nd half
Conditions-adjusted pace28°C · +214 m
Actual
3:40/km
Grade-adjusted
3:40/km
Heat-adjusted
3:29/km
−11s/km
True effort
3:29/km
−11s/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.