Joules per Beat: My heart energy!

If you record power and heart rate when you're cycling, then you can calculate the joules of energy delivered per heart-beat. This is a figure I haven't seen mentioned anywhere else, and I've made it possible to calculate the figure for each Strava activity that contains these data. This number will clearly vary from person to person, depending mostly on their heart capacity and muscular efficiency. For comparison, my 'typical' joules-per-beat is around 150 - 160. Note that in the calculation I subtract 60 bpm from the heart rate, to remove the effect of the typical resting heart rate.

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strava joules per beat

strava joules per beat


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by Osman Isvan on 16 December 2019
Very interesting! When power output changes suddenly, heart rate follows with a time constant. So, long activities with short bursts of above-average power (rolling hills, short sprints) may yield higher values (joules per heartbeat) than long steady state activities.
by John Swindells on 16 December 2019
Yes, that's my experience, with the heart rate remaining elevated (relative to power output) long after a big effort. This suggests that the cardio-vascular system starts working fairly inefficiently, so would presumably be causing premature fatigue waste of energy supply. Probably better to avoid those short, sharp bursts?
by Hector M on 08 October 2018
I'm wondering if it is a browser issue, or if this tool is partially broken... I don't see a result for Joules/Beat; just a column of zeros.
by John Swindells on 08 October 2018
Hi Hector, I'd somehow introduced a bug which meant that I wasn't getting the power from each activity. Thanks for pointing this out - all fixed now!
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by lucaP on 27 May 2016
very interesting figure! it would make more sense on selected segments, the total on a normal ride is not that significant (traffic, 'cruising along' segments etc)
by John Swindells on 27 May 2016
Good idea! That would need much more development work, but could be much more useful than the average for the entire activity.
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