How Much Energy?

I was bad this morning: I failed to get out of bed for the Kew Gardens 10k run that we'd signed up for over six months ago. Rosie didn't go either, in fact neither did the fit runner that she'd donated her race bib to.. Ah well. I then tried to compensate for it later in the morning by going for a 10k 'run' up the canal.


As I hadn't done any meaningful exercise since New Year, this distance proved to be an ordeal. Partly as a way to keep my mind off how hard this was going to be, I started thinking about how efficiently I could stretch out the limited amount of energy my legs had to dish out today, by running at the right pace / cadence / vertical oscillation etc. And then other energy-related stuff went through my head too..


"Union of Mind and Soul" (Goat song I had playing)

I wondered a bit about how much energy must be spent / wasted through a poor running style, and how much efficiency and performance could be saved through improvements here. I've no idea but it's probably about time I looked into this, and it chimes with some of the work / research we've been doing on industrial / domestic / transport energy efficiency.


I then started wonder a bit more about how the amount of energy exerted through strenuous exercise compares to other more relatable quantities of energy - like the amount of calories in a Weetabix (or Mars bar, tin of coke etc). In the past I've logged runs and only really paid attention to improvements in times. Now for the first time I was wondering how the estimate of calories clocked up during the run related to energy in a battery, boiling a kettle - and the Weetabix.


Once I'd stopped and got my breath back a bit, my Garmin said 931 'calories' (actually kcal). Sounded higher than it should have been for 10k distance - I guess it detected the extra lockdown baggage I was carrying, and the extra effort huffing + puffing.

Run summary with time hidden from view

We'd already programmed the energy of a Weetabix (at 68 kcal - see Reference* below) into our demo unit converter app which I'd written about before in our blog post Getting to Grips with Units. So this made it straightforward to quickly convert the units on the walk back for a shower. The 931 kcal I'd apparently burned off was equivalent to: around 1 kWh (3-4p of natural gas or ~16p of electricity); almost the full charge that a 12V car battery can take; around 11 kettle-boils - and almost 14 Weetabix!



I'm wondering if further mods to the app could perhaps have a broader usefulness in considering the body's energy balance for different kinds of exercise levels / durations and consumption of high-energy foods. Any comments or suggestions on this please let us know!


* Reference: Average nutritional values from the back of a Weetabix packet. 2 Weetabix = 136 kcal -> 1 Weetabix = 68 kcal.

Calorific value of a Weetabix

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