Field Manual

FM 21-20

Dept of the Army

30 Sept 1992

APPENDIX A

PHYSIOLOGICAL DIFFERENCES BETWEEN THE SEXES

Soldiers vary in their physical makeup. Each body reacts differently to varying degrees of physical stress,

and no two bodies react exactly the same way to the same physical stress. For everyone to get the maximum

benefit from training, leaders must be aware of these differences and plan the training to provide maximum

benefit for everyone. They must also be aware of the physiological differences between men and women.

While leaders must require equal efforts of men and women during the training period, they must also realize

that women have physiological limitations which generally preclude equal performance. The following

paragraphs describe the most important physical and physiological differences between men and women.

SIZE

The average 18- year-old man is 70.2 inches tall and weighs 144.8 pounds, whereas the average woman

of the same age is 64.4 inches tall and weighs 126.6 pounds. This difference in size affects the absolute

amount of physical work that can be performed by men and women.

MUSCLES

Men have 50 percent greater total muscle mass, based on weight, than do women. A woman who is the

same size as her male counterpart is generally only 80 percent as strong. Therefore, men usually have an

advantage in strength, speed, and power over women.

FAT

Women carry about 10 percentage points more body fat than do men of the same age. Men accumulate

fat primarily in the back, chest, and abdomen; women gain fat in the buttocks, arms, and thighs. Also,

because the center of gravity is lower in women than in men, women must overcome more resistance in

activities that require movement of the lower body.

BONES

Women have less bone mass than men, but their pelvic structure is wider. This difference gives men an

advantage in running efficiency.

HEART SIZE AND RATE

The average woman’s heart is 25 percent smaller than the average man’s. Thus, the man’s heart can pump

more blood with each beat. The larger heart size contributes to the slower resting heart rate (five to eight

beats a minute slower) in males. This lower rate is evident both at rest and at any given level of submaximal

exercise. Thus, for any given work rate, the faster heart rate means that most women will become fatigued

sooner than men.

FLEXIBILITY

Women generally are more flexible than men.

A-O

LUNGS

The lung capacity of men is 25 to 30 percent greater than that of women. This gives men still another

advantage in the processing of oxygen and in doing aerobic work such as running.