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An Observation on EPOC Load calculation

badbri
over 5 years ago

This isn't a bug or a support comment, just an observation on how the 945 calculates the EPOC "load" for an activity. 

This past weekend, I did a trail relay race.  I had 2 legs, each about 8m and they were separated by roughly 45min in between while my other runner was on the course doing his leg.

1st Leg - 66min - HR 156 avg - Power (from Stryd) 254w avg - Training Effect 3.1 - Load 75

2nd Leg - 74min - HR 156 avg - Power (from Stryd) 226w avg - Training Effect 4.3 - Load 171

So clearly, I had a rough go of it in my second leg, at the same HR effort I was a min/mile slower and watts were way down too.  Training Effect was definitely higher which is interesting but wowza that load really increased.  It got me curious as to how it's calculated so I grabbed this definition from Garmin's page:

EPOC

Exercise Load

The load of an exercise session is a numeric score indicating the degree of its impact on your body. It’s based on estimated EPOC. Garmin measures load for individual exercise sessions and also compiles load measurements for calculating weekly Training Load and Training Status.
Load & EPOC

After you complete a workout, your body continues to use oxygen at a higher rate than it would at rest (the “afterburn” effect). This phenomenon is known as excess post-exercise oxygen consumption, or EPOC. Since the oxygen your body consumes relates directly to the amount of energy it uses, EPOC is an excellent measure of exercise load. It quantifies how much work your body has to do to get back to normal.

Using Load for Training

Exercise Load is useful for measuring the intensity of different workouts compared to one another. In general, higher load numbers equal more impactful training, but there is value in having a balance of higher and lower load scores for recovery purposes.

  • 0 over 5 years ago

    One differnce will likely be cardiac drift between the 2 legs. ie. your heart rate will have ramped up faster in the first 5-10 minutes in the 2nd leg than it did in the first. This will give you more time spent in the relevant HR zones, even if you ran the 2 legs exactly the same in terms of pace.

    The other thing is how sensitive EPOC and TE is to your peak efforts. Unfortunately Garmin doesn't make EPOC visible, but my old Suunto did. And you only had to run an interval or a hill slightly faster, or shorten the recovery interval slightly, for it to make a big difference to EPOC and TE, even if it got lost in the overall average pace/HR of a long run.

  • 0 over 5 years ago in reply to mcalista

    Yeah a difference from a 75 load to 171 is massive.  I think the key element is the statement in their definition about "afterburn effect."  Obviously having just run 45min prior I was still in that afterburn zone.