Testosterone is a steroid hormone that is primarily secreted by the testes in male subjects and the ovaries in female subjects. Smaller amounts of testosterone are secreted by the adrenal glands in both sexes, with adrenal secretion playing a significant role in resistance exercise-induced raises in some women. Testosterone produces both anabolic (tissue building) and androgenic (secondary sexual characteristics) effects in the body. Anabolic effects include increasing musculoskeletal mass and strength.
Resistance exercise produces an acute increase in total testosterone concentrations in men (3), whereas the results in young women have been equivocal, with some showing no change and other research showing elevations (9). Acute serum total testosterone responses after resistance training are influenced by several factors, including exercise selection, intensity and volume, training experience, caloric intake, and protein/carbohydrate supplementation (12,16). Exercises that use a large amount of muscle mass, such as the Olympic lifts (e.g., clean and jerk; snatch), squats, and dead lift, produce larger elevations when compared with single-joint exercises using a smaller muscle mass. High-volume, moderate-intensity training sessions with short rest intervals (i.e., 3 to 4 sets of 10 to 20 repetitions at 50% to 70% of 1 RM, 2-minute rest periods) have been shown to produce greater testosterone increases than traditional strength training protocols that use high-load, multi-set training sessions with long (3-minute) rest intervals between sets (9,10).
Estrogens are steroid hormones that are synthesized and secreted by the ovaries and adrenal glands in women. Men also produce estrogen through a conversion process known as aromatization. Estrogens perform various bodily functions including the slowing of bone and muscle loss during aging. Research has shown differences in the rate of muscle decrement during aging between men and women, and this difference may be due to changes in sex hormones (13). Whereas lower testosterone levels in men contribute to the decline in muscle strength, the relationship between estrogen levels in women to muscle strength loss is less understood.
Studies show an accelerated loss of muscle and strength immediately after menopause. Estrogen may play a protective role in muscle strength and quality through the actions of the estrogen receptor (ER). Dieli-Conwright et al. (7) found greater enhancements of ER activity after a single eccentric exercise bout in postmenopausal women using hormone replacement therapy, compared with controls. This suggests that estrogen plays an important role in the development of muscle after resistance exercise. Fitness professionals should recognize the varying roles estrogen plays in the female body and understand that muscle mass and strength gains may be influenced by menopause and/or if the client is taking estrogen replacement medication.
Resistance exercise elicits an impressive response in various hormone concentrations of the body that are central for muscle growth and repair (Table). This acute hormonal response seems to be influenced by the exercise stimulus (i.e., intensity, volume, muscle mass involved, rest intervals, frequency). It is hoped, from this brief review of acute hormonal responses of resistance exercise, that exercise professionals will be able to better explain, describe, and communicate to their clients and students how the development of muscle strength and endurance occurs.
Hormones play a significant role in the body’s response to resistance exercise. Muscle mass, strength, and body composition are influenced by the hormonal responses after resistance exercise. Manipulating acute program variables, such as volume, intensity, rest between sets, exercise selection, the muscle mass involved, and workout duration, can impact acute hormonal responses associated with resistance exercise.
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