Long run · Saturday, 19 September 2026 · Week 4, Durability Base
A long run holds together despite real time over cap
27 weeks to MDS
Forty three per cent of this run sat above the heart rate cap, even though the average landed one under it. That gap between the two numbers is exactly why I don't trust the average on its own.
On Saturday 19 September I covered the week four long run as planned, through humid, windy conditions with 781 feet of climbing. Pace eased from 12:21 in the first mile to 13:12 in the last, but heart rate barely moved with it, and the efficiency fade came in at just one per cent, well inside the band I coach to.
So the effort held its shape even with all that time over cap. That combination looked fine today. I want to see whether it repeats on the next long run before I read anything more into it.
- Distance
- 12.1 mi
- 19.4 km
- Moving time
- 2h 42m
- started 09:24
- Average pace
- 13:28
- per mile
- Heart rate
- 125
- average · max 149
- Climb
- 781 ft
- 238 m
- Conditions
- 19°C
- 81% humidity · wind 25 km/h
Planned long run, full distance.
Heart rate against my cap
My easy running has a heart rate ceiling of 126 bpm. It keeps the effort aerobic while my legs, tendons and joints catch up with the mileage. A run counts as over the cap when the average is more than 2 beats over it, or more than a fifth of the time sits above it.
Over the cap. Average 125 bpm, with 29% of the run above 126. The fix is to slow down, walk the steeper bits if I need to, and let it settle.
How well the running held up
I compare how efficiently I was running early in the run (speed for each heartbeat, corrected for hills) with the late part. The drop was 1%. Under 5% is what I call held. That band is a coaching convention, not a validated threshold.
Late on, pace slowed 5.5% and heart rate fell 4.5%.
Confidence: medium (the hill correction changed this reading by about 7 points, and it is an estimate).
First half against second half
Comparing pace against heart rate in the first half with the second, the gap was 0.5%. Under 5% is the convention I coach to: it suggests the aerobic side coped with the length of the run. It says nothing about why.
Mile by mile
| Mile | Pace | Avg HR | Climb |
|---|---|---|---|
| 1 | 12:21 | 122 | 89 ft |
| 2 | 12:47 | 127 | 13 ft |
| 3 | 14:52 | 126 | 128 ft |
| 4 | 13:57 | 127 | 95 ft |
| 5 | 13:28 | 128 | 46 ft |
| 6 | 12:47 | 124 | 7 ft |
| 7 | 14:12 | 124 | 128 ft |
| 8 | 13:19 | 128 | 52 ft |
| 9 | 13:14 | 120 | 52 ft |
| 10 | 15:05 | 119 | 108 ft |
| 11 | 12:34 | 125 | 7 ft |
| 12 | 13:12 | 126 | 13 ft |
Heart rate in orange is above the 126 bpm cap.
Figures from my watch via Intervals.icu, read by the Ultra Event Training app. Heart rate from a watch is a proxy for effort, not a lab measure. The efficiency figures compare speed per heartbeat early and late in a run with a hill correction; they show what changed, not the cause.