Resistance Training Boosts Sex Steroid Production in Older Men

A new study finds that resistance training can increase the production of sex steroids in the muscles of older men. In a new paper, researchers from Ritsumeikan University in Kyoto, Japan explain that, while the testes, ovaries, and adrenal cortex produce most steroid sex hormones in humans, recent animal work has shown that skeletal muscle can also synthesize testosterone, estradiol, dehyroepiandrosterone (DHEA), and dihydrotestosterone (DHT). To gauge the effect resistance training might have on older men over a longer period of training, the researchers recruited 13 men with a mean age of 67.2 years, and 6 men with a mean age of 24.3. The subjects were moderately active, but none regularly performed resistance exercises. As part of the 12-week study, the older men performed knee extensions and flexions 3 times a week on alternate days, using starting weights that were 70 percent of each subject's single-repetition maximum strength. Trainers retested this measurement and adjusted weights for each of these men every 4 weeks. Levels of sex steroid hormones and precursors in each man's vastus lateralis—the largest muscle in the quadriceps—were measured by biopsy before the weight training. The same measurement was taken again in the older men after the weight training. Researchers also sampled the hormones in the men's blood and measured the size of their quadriceps before and after the training, finding the older men had much lower levels of steroidogenic enzymes, as well as sex steroid hormones and insulin-like growth factor (IGF-1), than the younger men in both their blood and their muscles. The older men were also weaker and had smaller quadriceps. Nevertheless, the levels of sex steroid hormones increased significantly in the older men's muscles after the weight training. The older men's isokinetic extension strength and quadriceps sizes also increased substantially. While levels of steroidogenic enzymes as well as their androgen-receptor protein expression significantly increased, investigators found that, in the blood, the older mens’ serum free testosterone did not substantially rise, nor did serum IGF-1. The authors found a significant correlation between muscular steroid hormone levels and muscle strength and size, leading them to conclude that “progressive resistance training seems to restore muscle sex steroid hormone levels via enhancement of steroidogenesis-related enzyme expressions in the skeletal muscle and may partly contribute to the increase in muscle strength and [size].” The authors note that further research is needed, but say the findings could have important implications for a wide range of conditions experienced by many aging individuals and linked to a decline in sex steroid hormones. "Resistance training–induced increased muscular sex steroid hormone may positively affect age-related concerns such as accidental falls, diabetes, sarcopenia, and osteoporosis,” the authors wrote, “and may improve the quality of life for older individuals.” —Mark McGraw Reference Sato K, Iemitsu M, et al. Resistance training restores muscle sex steroid hormone steroidogenesis in older men. Journal of the Federation of American Societies for Experimental Biology. 2014.