According to the University of Maryland Medical Center, body hair is one of the secondary sex characteristics and its growth is partially regulated by hormones. Working out regularly, getting enough rest, hydrating and eating correctly all foster proper hormone balance. Hair growth is directly affected by the health of your body's ability to secrete and then deliver hormones to their intended targets.
According to the Mayo Clinic, the hormone testosterone helps to maintain muscle mass. Although its use by amateur and professional athletes is illegal in many countries — including the United States — some athletes have used testosterone or anabolic steroids in their desire to boost the intensity or effectiveness of their workouts. Consequently, some have experienced side effects from this practice; one such adverse effect can be hair loss. Some steroid users — including females — may develop body hair, including facial hair.
Excessive amounts of stress can cause hair loss. Hair cells can shut down to redirect energy to places where it is needed. Moderate exercise performed regularly can reduce stress. When you exercise, you burn up nervous energy and your body controls the systematic release of chemical neurotransmitters known as endorphins. These circulate through your body, providing a calming effect. The production level of endorphins differs from one person to another.
Exercise is a key component of improving health in people who suffer from many diseases affecting circulation to the lower extremities. Conditions such as diabetes, heart disease and peripheral artery disease can cause legs to lose their hair. A workout that improves circulation may increase the healthy growth of body hair by getting oxygen and nutrients to the hair follicles.
The Role of Genetics
If you notice a dramatic increase or loss of body hair — particularly if it happens suddenly — you should alert your doctor. Dramatic hair loss or increase can be signs that something unusual is occurring in your body. A sensible amount of exercise is one of many precautions you can take to protect healthy hair growth, but genetics plays a strong role in the fate of your hair line. Women as well as men can lose hair naturally, and even the best exercise routine can't change your DNA.