How to Tell if Your Long Run Actually Worked
The one number that tells you whether a long run did its job, and almost nobody looks at it: aerobic decoupling.
You finish a long run, get the green checkmark and some kudos, and assume it worked.
There's one number that tells you whether it actually did, and almost nobody looks at it.
Aerobic decoupling
It measures how much harder your heart had to work in the second half of a run to hold the same pace as the first half. Your watch has already recorded everything you need to calculate it.
The 4 tiers
Under 3%: the junk long run. It cost you recovery but didn't send much of a signal.
3 to 5%: the sweet spot.
5 to 10%: the accidental workout. Your base isn't there for that duration yet.
10%+: you're not ready for this distance yet.
How to check yours
Screenshot your splits, including heart rate by mile or kilometer, and paste them into the prompt. You get a verdict plus ways to improve and track it through your block.
Mine came out well below 3%, so I may have gone a bit too easy.
FYI: a low number isn't automatically a gold star, and one run isn't a trend. The real test is the same run tracked over 6 to 8 weeks. The guide covers that too.
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