Intervalsconfidence 0.83
4 × 2km
Colin Dismuke50 km / marathon build
Source: own Strava export
Intervals
4 × 2km
Distance
16.1 km
Moving
69:51
Rep pace
3:43/km
Avg HR
168 bpm
Reps
4
Planned vs actual · TrainingPeaksPlanned 1:12:45 · 16.3 kmRan 1:09:51 · 16.1 kmIF 1.40TSS 227
Shape of the sessionEasyWorkFastest
warm up
cool down
0:004 × work / float69:51
The decode
This was a 4 × 2km repeat set ahead of a half-marathon simulation, with reps one and three assigned half-marathon pace and reps two and four intended faster. The recoveries were 60s static rests.
The pattern matched the prescription: 3:44/km, 3:40/km, 3:46/km and 3:40/km, with heart rate rising from 178 to 184. The third rep dipped, but the set closed at the pace of the second rep.
Rep splits
| Rep | Time | Pace | HR | Float |
|---|---|---|---|---|
| 1 | 7:29 | 3:44/km | 178 | 1:00 |
| 2 | 7:20 | 3:40/km | 182 | 1:00 |
| 3 | 7:32 | 3:46/km | 182 | 1:00 |
| 4 | 7:19 | 3:40/km | 184 | 1:00 |
0.83
confidence
What the engine saw
- 4 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
Recovery6%
Z2
Endurance23%
Z3
Tempo10%
Z4
Threshold23%
Z5
VO₂max38%
Pace
Z1
Easy24%
Z2
Endurance35%
Z3
Tempo26%
Z4
Threshold14%
Z5
VO₂max0%
Z6
Speed0%
Power
Z1
Recovery10%
Z2
Endurance9%
Z3
Tempo34%
Z4
Threshold32%
Z5
VO₂max12%
Z6
Anaerobic3%
Z7
Neuro0%
Aerobic decoupling · Pa:HR+6.9%
Effort & efficiency
0.73
Running effectiveness
speed per watt/kg, reps
6.2 w/kg
Power-to-weight
rep average
2.57
Efficiency factor
norm. power per bpm
1.06
Variability index
1.0 = perfectly even power
1.3%
Rep consistency
pace spread across reps, lower is tighter
1869 kJ
Total work
mechanical energy
1181 kcal
Energy
estimated burn
814 bpk
Cardiac cost
heartbeats per km
61%
Above threshold
≥ 164 bpm (Z4+)
+0:11/km
Split balance
positive split, slower 2nd half
Conditions-adjusted pace32°C · +58 m
Actual
3:42/km
Grade-adjusted
3:42/km
Heat-adjusted
3:28/km
−14s/km
True effort
3:28/km
−14s/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.