Context: Testosterone increases skeletal muscle mass and strength, but the effects of testosterone on aerobic performance in mobility-limited older men have not been evaluated.
Objective: To determine the effects of testosterone supplementation on aerobic performance, assessed as peak oxygen uptake (V̇O2peak) and gas exchange lactate threshold (V̇O2θ), during symptom-limited incremental cycle ergometer exercise.
Design: Subgroup analysis of the Testosterone in Older Men with Mobility Limitations Trial.
Setting: Exercise physiology laboratory in an academic medical center.
Participants: Sixty-four mobility-limited men 65 years or older with low total (100-350 ng/dL) or free (<50 pg/dL) testosterone.
Interventions: Participants were randomized to receive 100-mg testosterone gel or placebo gel daily for 6 months.
Main outcome measures: V̇O2peak and V̇O2θ from a symptom-limited cycle exercise test.
Results: Mean (SD) baseline V̇O2peak was 20.5 (4.3) and 19.9 (4.7) mL/kg/min for testosterone and placebo, respectively. V̇O2peak increased by 0.83 (2.4) mL/kg/min in testosterone but decreased by -0.89 (2.5) mL/kg/min in placebo (P = .035); between group difference in change in V̇O2peak was significant (P = .006). This 6-month reduction in placebo was greater than the expected -0.4-mL/kg/min/y rate of decline in the general population. V̇O2θ did not change significantly in testosterone but decreased by 1.1 (1.8) mL/kg/min in placebo, P = .011 for between-group comparisons. Hemoglobin increased by 1.0 ± 3.5 and 0.1 ± 0.8 g/dL in testosterone and placebo groups, respectively.
Conclusion: Testosterone supplementation in mobility-limited older men increased hemoglobin and attenuated the age-related declines in V̇O2peak and V̇O2θ. Long-term intervention studies are needed to determine the durability of this effect.