Work, Power, Energy And Efficiency In Humans

BY: Sheila Mae Liquit BEED-GENERALIST

Metabolic Rates the rate of conversion of food energy to some another form while the total rate of a person at rest is called basal metabolic rate (BMR).

Example Problem:

How many grams of fat will an idle person gain in a day by consuming 2500 kcal of food?

Solution: First, calculate the energy requirement in kilocalories on the data in Table 4 .4

(1.22kcal)(60min/hr)(24hr/day) = 1757 kcal/day

So the number of excess kilocalories is

2500 kcal – 1757 kcal = 743 kcal

Cont.

Using the food value for fat from table 4.1 and assuming that the same amount of energy is used to store a gram of fat as is obtained from digesting a gram of fat, we see that

Mass gain = 743 kcal x 1.0 g fat 9.3 kcal

Mass gain = 80 g fat

Efficiency and Human Activity

Human efficiency is defined as useful work output divided by energy input:

Eff = W out/ E in

or in power input:

Eff = P out/ P in

where P out is defined as useful work per unit time.

Why does body efficiency vary with activity?

It basically depends on how many muscles are used cooperatively to produce work and on the energy used by the other organs. The more muscles used to produce useful work compared with the activity of other organs, the more efficient the body is.

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