Why Does Weight Training Work for Women

Varying weight training intensity increases growth hormone in women

Women who undertake a long-term weight training program produce more biologically active growth hormone, a finding that allows physiologists to understand why weight training improves muscle tone and optimizes metabolic function.

A study published in the December issue of the American Journal of Physiology-Endocrinology and Metabolism looked at different forms of growth hormone, used different testing methods, and varied weight training regimens. The research found that the role of growth hormone in women's muscle development may be more complicated than previously thought.

"We found that growth hormone was responsive to moderate and heavy exercise regimens having 3-12 repetitions with varying weight loading," said the study's principal author, William J. Kraemer. "Women need to have heavy loading cycle or workout in their resistance training routines, as it helps to build muscle and bone."

The researchers made these findings:

• The presence of growth hormone varied with the training regimen.

• The presence of growth hormone varied with the test used to detect it. This suggests that pituitary function and the release of different sizes of growth hormone is altered with weight training.

• The body can adapt and produce more or less of certain sizes of growth hormone with weight training. In this study, the larger sized growth hormone variants appear to increase with heavy resistance training.

"This study shows that not every form of growth hormone responds in the same way, but is dependent upon the exercise protocol," Kraemer explained. "This may forever change the way we look at growth hormone in the circulation with exercise and training."

This study was supported by a grant from the US Department of Defense Women's Health Initiative.

Note: This story has been adapted from a news release issued by American Physiological Society.