## Meter Gauges Work in Bread-Slice Units (May, 1938)

Why is there a basketball team watching the girl ride? And also, doesn’t almost one slice per minute seem a bit high?

Meter Gauges Work in Bread-Slice Units

How rapidly exercise uses up the energy in the food you eat is graphically demonstrated by a device called the “bread-o-meter” at the Franklin Institute in Philadelphia, Pa. When a visitor mounts a bicycle frame and pedals vigorously, a generator produces electricity in proportion to his effort, and figures on a board show how many slices or loaves of bread would be needed to furnish this energy.

1. Charlene says: July 22, 20119:27 am

It is too high: white bread contains on average 80 calories* per slice, while a 120 lb woman using a stationary bike vigorously for ten minutes would burn 103 calories.

*Or kcal in both instances, to be precise

2. Charlene says: July 22, 20119:29 am

Looking at it again, though, I’m not sure how they get “energy used” from the amount of electricity produced.

3. Hirudinea says: July 22, 201112:21 pm

Reminds me of a display they had at the Ontario Science Centre, you would peddle a bike to produce electricity to run a (tube) tv, let me tell you, you didn’t want to watch a long movie on that tv!

4. John Savard says: July 23, 20117:22 am

Well, a kilowatt-hour is a unit of energy, and so is a joule, and so is a kilocalorie. So one just needs a conversion factor to determine, from the number of kWh one produces on the bicycle, how many kCal one has burned. (When one is told that a certain portion of food has “100 calories”, it actually means 100 kilocalories, where a calorie is the energy required to raise the temperature of one gram of water by one degree Celsius.)

Of course, a correction factor would be needed as well to cover inefficiencies in the generator, the bicycle, and the human body.

However, while the apparatus shows that the human body can produce work, the fact that bread has caloric content is merely asserted by the display; it is not in any way demonstrated by it. That is the flaw I see here.

That a pretty girl is exercising, while the members of a (basketball?) team are just standing around watching is, of course, slightly amusing as well.

5. whoozle whaazle says: November 14, 20115:40 pm

Hey Charlene,

I think the Calgary Science Centre (now called the Telus Spark Science Centre) had something like this. If you were good enough you could have powered up a lightbulb, a fan, and even a mini-television set ! :O

(it was really hard to keep the television set going though haha)