I found something in my logs I don’t understand. On the podcast, @Chad has said that Kcal of energy use and KJ of work performed are roughly equivalent since 1 Kcal = 4.18 KJ, but the human body is roughly 24% efficient so needs to burn 4 Kcal to actually do ~4 KJ of work. That matches everything else I’ve ever heard and makes sense.
But when I look at the 51 outside rides in my logs (data from Quarq PM, recorded by Wahoo ELEMNT, uploaded to Strava, analyzed on Veloviewer), I see very different numbers. The average ratio of Kcal to KJ is shown as 2.20 with a standard deviation of 0.26, so ~95% are between 1.7-2.7 Kcal/KJ. My big rides are around 1500 KJ of work, and there’s a big difference between “refueling” 1500 Kcal or 3000+ KCal!
Are Strava (or my ELEMNT) just guessing, and not very well at that? Or are those numbers a reasonable representation of the additional “energy cost” of riding outside in the Florida heat/humidity/sun and having to cool the body down much more than usual?