Intervalsconfidence 0.83
20-16-12-4-4
Colin Dismuke50 km / marathon build
Source: own Strava export
Intervals
20-16-12-4-4
Distance
16.6 km
Moving
74:33
Rep pace
4:22/km
Avg HR
166 bpm
Reps
3
Planned vs actual · TrainingPeaksPlanned 1:20:00Ran 1:14:33 · 16.6 kmIF 1.51TSS 283
Shape of the sessionEasyWorkFastest
cool down
0:003 × work / float74:33
The decode
This was a marathon-pace progression. The descending work blocks and 120-second recoveries kept the session under continuous aerobic pressure, with limited reset between efforts.
The 20-minute, 16-minute, and 12-minute blocks ran at 4:06/km, 4:08/km, and 4:07/km as heart rate rose from 171 to 174 and 175. The later 4-minute efforts reached 3:59/km and 4:04/km at 174 and 172, so the set held together rather than fading.
Rep splits
| Rep | Time | Pace | HR | Float |
|---|---|---|---|---|
| 1 | 10:00 | 4:51/km | 140 | — |
| 2 | 16:00 | 4:08/km | 174 | 2:00 |
| 3 | 12:00 | 4:07/km | 175 | 2:00 |
0.83
confidence
What the engine saw
- 3 work intervals detected from lap markers, confirmed by clear pace separation.
- Recoveries average 120s.
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
Recovery12%
Z2
Endurance17%
Z3
Tempo3%
Z4
Threshold31%
Z5
VO₂max36%
Pace
Z1
Easy30%
Z2
Endurance39%
Z3
Tempo31%
Z4
Threshold0%
Z5
VO₂max0%
Z6
Speed0%
Power
Z1
Recovery16%
Z2
Endurance3%
Z3
Tempo38%
Z4
Threshold40%
Z5
VO₂max2%
Z6
Anaerobic0%
Z7
Neuro0%
Aerobic decoupling · Pa:HR+9.4%
Effort & efficiency
0.73
Running effectiveness
speed per watt/kg, reps
5.3 w/kg
Power-to-weight
rep average
2.48
Efficiency factor
norm. power per bpm
1.06
Variability index
1.0 = perfectly even power
7.9%
Rep consistency
pace spread across reps, lower is tighter
1837 kJ
Total work
mechanical energy
1202 kcal
Energy
estimated burn
818 bpk
Cardiac cost
heartbeats per km
67%
Above threshold
≥ 164 bpm (Z4+)
-0:07/km
Split balance
negative split, faster 2nd half
Conditions-adjusted pace34°C · +70 m
Actual
4:21/km
Grade-adjusted
4:21/km
Heat-adjusted
4:02/km
−19s/km
True effort
4:02/km
−19s/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.