Every time I come back from riding my bike, the bike computer tells me,
among other useful information like my pulse rate, how high the hills
were, how fast I pedalled, what my road speed was, the temperature,
rates of descent, etc, etc, etc, much more stuff which I have my
computer print out in neat graphs. Among all this the bike computer
tells me how many watts I expended. The thing cheats of course, as it
takes a downhill or level-road ride as zero watts (you're still
expending energy). It gives peak output and an average for the ride. So
the energy expended is the length of the ride (it only ticks the clock
when the wheels are moving) multiplied by the average output. But get
this, one kilowatt-hour is 860kJ. So, if you've gone for a ride that
will burst your average audiophile (middle-aged, overweight, fatarsed,
except for Patrick and me, who are ex-athletes and cyclists still) out
into heavy perspiration, say 100W average for an hour, which allows for
some extended peaks at 250W which will drive his heartbeat up to the
maximum, which does no one any good, is 0.1kW or 86kJ. In other words,
an hour's hard ride burns only 86 nutritional calories. You see, those
calories on food packets are really kiloJoules aka "nutritional
calories". You guys better stop eating altogether or you'll have to be
on your bikes eight hours a day.

Obligatory on-topic comment: That's a worse scam than rating audio gear
in "RMS watts" or "music watts".

Andre Jute
The trouble with most people is not what they don't know, but what they
know for certain that isn't true. ---Mark Twain