Long run · Sunday, 27 September 2026 · Week 5, Durability Base
Long run runs hot but the effort holds together
26 weeks to MDS
Twelve point one miles, the long run for week five, a little short of the plan. Windy conditions and 817 feet of climbing filled the two hours and forty one minutes out there.
The average heart rate landed one over the cap, and more than half the run sat above it, time the average on its own does not reveal. Pace slipped from 12:32 for the first mile to 13:35 for the last full one, but heart rate barely moved between the two, and efficiency fade came out at 3.3 percent, inside the range I treat as held. Decoupling was low too, at 2.2 percent.
So the effort ran hotter than the cap allows, even as the underlying running stayed steady. I will look at whether that pattern repeats on the next long effort, or whether the wind and climb here explain most of it.
- Distance
- 12.1 mi
- 19.4 km
- Moving time
- 2h 41m
- started 15:11
- Average pace
- 13:22
- per mile
- Heart rate
- 127
- average · max 147
- Climb
- 817 ft
- 249 m
- Conditions
- 19°C
- 72% humidity · wind 23 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 127 bpm, with 39% 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 3.3%. Under 5% is what I call held. That band is a coaching convention, not a validated threshold.
A sustained drop began around 2h 09m into the run.
Late on, pace slowed 2.8% and heart rate rose 0.6%.
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 2.2%. 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 | 12:32 | 128 | 95 ft |
| 2 | 12:58 | 125 | 20 ft |
| 3 | 14:38 | 130 | 128 ft |
| 4 | 14:07 | 128 | 89 ft |
| 5 | 13:10 | 124 | 39 ft |
| 6 | 12:26 | 124 | 7 ft |
| 7 | 14:03 | 122 | 135 ft |
| 8 | 13:22 | 128 | 39 ft |
| 9 | 13:19 | 126 | 66 ft |
| 10 | 13:49 | 130 | 95 ft |
| 11 | 12:48 | 127 | 7 ft |
| 12 | 13:35 | 129 | 59 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.