This document discusses work, power, energy, and efficiency in humans. It provides an example problem calculating the grams of fat an idle person would gain in a day consuming 2500 kcal of food (80g). It defines human efficiency as useful work output divided by energy input. Efficiency varies with activity, as it depends on how many muscles are used cooperatively to produce work compared to the energy used by other organs - the more muscles producing useful work, the more efficient the body is.

1. Work, Power, Energy
And Efficiency In Humans
BY: Sheila Mae Liquit
BEED-GENERALIST

2. 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).

3. Example Problem:
How many grams of fat
will an idle person gain in a day by
consuming 2500 kcal of food?

4. 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

5. 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

6. 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.

7. Why does body efficiency
vary with activity?

8. 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.

9. thank you! 