Changes in muscle mass, muscle strength, and power but not physical function are related to testosterone dose in healthy older men

Abstract

Objectives: To examine the effect of graded doses of testosterone on physical function and muscle performance in healthy, older men.

Design: Randomized, double-blind, placebo-controlled clinical trial.

Setting: General clinical research center.

Participants: Community-dwelling healthy men aged 60 to 75 (N=44).

Intervention: Monthly treatment with a gonadotropin-releasing hormone agonist plus 25, 50, 125, or 300 mg/wk of intramuscular injections of testosterone enanthate for 20 weeks.

Measurements: Skeletal muscle mass (SMM) was estimated using dual-energy X-ray absorptiometry. Leg press strength was measured by one repetition maximum, leg power by Nottingham Leg Rig, and muscle fatigability by repetitions to failure in the leg press exercise. Stair climbing, 6-meter and 400-meter walking speed, and a timed-up-and-go (TUG) test were used to assess physical function.

Results: Significant testosterone dose- and concentration-dependent increases were observed in SMM (P<.001) and maximal strength (P=.001) but not muscle fatigability. Leg power also increased dose-dependently (P=.048). In contrast, changes in self-selected normal and fast walking speed over 6 or 400 meters, stair climbing power, and time for the TUG were not significantly related to testosterone dose, testosterone concentrations, or changes in muscle strength or power, or SMM.

Conclusion: Testosterone administration was associated with dose-dependent increases in SMM, leg strength, and power but did not improve muscle fatigability or physical function. The observation that physical function scores did not improve linearly with strength suggests that these high-functioning older men were already in the asymptotic region of the curve describing the relationship between physical function and strength.

Figure 1

Changes from baseline after 20 weeks of treatment with a GnRH agonist plus one of five weekly doses of testosterone enanthate. Error bars are SE. Means with the same letter are significantly different. Panel A: Skeletal muscle mass: Overall ANOVA, P < 0.001; a = P < 0.001; b = P < 0.001; c = P < 0.01; d = P < 0.001. (Panel B), 1-RM leg press strength: Overall ANOVA, P < 0.001; a = P < 0.01; b = P < 0.001; c = P < 0.001; d = P < 0.05. Panel C: Leg press power: Overall ANOVA, P = 0.048; there were no pairs of mean changes that were significantly different, P > 0.05. Panel D Leg press fatigability: Overall ANOVA, P = 0.407.

Figure 2

Changes from baseline in six measures of physical performance after 20 weeks of treatment with a GnRH agonist plus one of five weekly doses of testosterone enanthate. Error bars are SE. Panel A: 4-step stair climb; Panel B modified Margaria stair climb; Panel C: 6-m walk, usual pace; Panel D: 6-m walk, fast pace; Panel E: 400-m fast pace; Panel F: timed up-and-go. There were no significant differences between any of the mean changes for any of the six measures of physical performance, P > 0.05.