Intervalsconfidence 0.83
4 × 2km
Colin Dismuke50 km / marathon build
Source: own Strava export
Intervals
4 × 2km
Distance
12.6 km
Moving
54:24
Rep pace
3:46/km
Avg HR
162 bpm
Reps
4
Planned vs actual · TrainingPeaksPlanned 53:27 · 12.1 kmRan 54:24 · 12.6 kmIF 1.38TSS 172
Shape of the sessionEasyWorkFastest
warm up
cool down
0:004 × work / float54:24
The decode
This was a four-by-2km repeat session with 60-second static recoveries. The first and third reps were assigned at marathon goal race pace or slightly faster; the second and fourth were the hard efforts.
The reps ran in 7:44, 7:22, 7:42 and 7:15, from 3:52/km to 3:38/km. Heart rate rose from 169 to 178, and the set closed with its fastest rep after the third rep had slowed to 3:51/km.
Rep splits
| Rep | Time | Pace | HR | Float |
|---|---|---|---|---|
| 1 | 7:44 | 3:52/km | 169 | 1:00 |
| 2 | 7:22 | 3:41/km | 174 | 1:00 |
| 3 | 7:42 | 3:51/km | 175 | 1:00 |
| 4 | 7:15 | 3:38/km | 178 | 1:00 |
0.83
confidence
What the engine saw
- 4 work intervals detected from lap markers, confirmed by clear pace separation.
- Rep paces descend across the set (a cut-down / progression).
- 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
Recovery15%
Z2
Endurance22%
Z3
Tempo10%
Z4
Threshold22%
Z5
VO₂max30%
Pace
Z1
Easy41%
Z2
Endurance7%
Z3
Tempo41%
Z4
Threshold10%
Z5
VO₂max1%
Z6
Speed0%
Power
Z1
Recovery7%
Z2
Endurance10%
Z3
Tempo30%
Z4
Threshold45%
Z5
VO₂max7%
Z6
Anaerobic0%
Z7
Neuro0%
Aerobic decoupling · Pa:HR+6.4%
Effort & efficiency
0.74
Running effectiveness
speed per watt/kg, reps
6.0 w/kg
Power-to-weight
rep average
2.59
Efficiency factor
norm. power per bpm
1.06
Variability index
1.0 = perfectly even power
2.8%
Rep consistency
pace spread across reps, lower is tighter
1338 kJ
Total work
mechanical energy
888 kcal
Energy
estimated burn
721 bpk
Cardiac cost
heartbeats per km
52%
Above threshold
≥ 164 bpm (Z4+)
-0:04/km
Split balance
negative split, faster 2nd half
Conditions-adjusted pace25°C · +39 m
Actual
3:45/km
Grade-adjusted
3:45/km
Heat-adjusted
3:37/km
−8s/km
True effort
3:37/km
−8s/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.