On 17/03/14 20:09, Chris wrote:
The gym has machines by pulsefitness.
There seems to be a mismatch in the numbers displayed.

After a bike session the summary was:
Power average: 74 Watts.
Time taken: 9 minutes.
Energy used: 50 kcal.

The above energy figure would equate to 333 kcal per hour.
But 100 Watts is only 86 kcal per hour!

The mismatch is so enormous that I feel I must have missed something.
I would be grateful to any physicist who can shed light on the figures.

I think the 74 watts is power output (as developed in the machine doing
the measuring) - and the 50 Calories is the amount of bio-energy burnt
to develop that.

In this example, you have developed 9.5 Calories (or kcal) at the
expense of 50, so about 20% efficient.

Whilst I have no idea for sure, that seems believable for a biological
process.