Raceconfidence 0.80
Perth Half Marathon
Colin Dismuke50 km / marathon build
Source: own Strava export
Race
Perth Half Marathon
Distance
21.3 km
Moving
90:18
Avg HR
178 bpm
Shape of the sessionEasyWorkFastest
0:00session90:18
The decode
This was a 21.31 km race, paced as a sustained effort rather than a split session. The absence of recovery periods made pressure accumulate across the full distance.
The pace held broadly even through 20 km, then fell to 4:56/km on lap 21 while heart rate remained high at 189 bpm. Heart rate rose to 193 bpm across laps 17-20 and reached 195 bpm, showing a late loss of pace under sustained load.
0.80
confidence
What the engine saw
- Raced 21.3 km at 178 bpm avg, even pacing held under pressure (CV 4%).
- Matches the athlete's own session label.
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
Recovery11%
Z2
Endurance6%
Z3
Tempo0%
Z4
Threshold0%
Z5
VO₂max83%
Pace
Z1
Easy2%
Z2
Endurance81%
Z3
Tempo15%
Z4
Threshold1%
Z5
VO₂max0%
Z6
Speed0%
Power
Z1
Recovery1%
Z2
Endurance0%
Z3
Tempo53%
Z4
Threshold43%
Z5
VO₂max2%
Z6
Anaerobic0%
Z7
Neuro0%
Aerobic decoupling · Pa:HR+14.4%
Effort & efficiency
0.72
Running effectiveness
speed per watt/kg, reps
5.5 w/kg
Power-to-weight
rep average
2.36
Efficiency factor
norm. power per bpm
1.01
Variability index
1.0 = perfectly even power
4.6%
Rep consistency
pace spread across reps, lower is tighter
2265 kJ
Total work
mechanical energy
1535 kcal
Energy
estimated burn
758 bpk
Cardiac cost
heartbeats per km
83%
Above threshold
≥ 164 bpm (Z4+)
+0:04/km
Split balance
positive split, slower 2nd half
Conditions-adjusted pace26°C · +89 m
Actual
4:14/km
Grade-adjusted
4:14/km
Heat-adjusted
4:03/km
−11s/km
True effort
4:03/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.