Figure 1. Effect of testosterone supplementation plus low-intensity physical training on grip strength, spontaneous physical activity, and respiratory activity in old male mice.

(A) Forelimb grip strength measured at baseline (wk 0, N = 8 per group, C: control, T: testosterone) and after 7 weeks of (N = 6 for control, N = 8 for T group) testosterone supplementation (10 mg/kg, sc, twice per week). Control was injected with an equal volume of vehicle (0.1 ml). (B) Spontaneous physical movements recorded as total counts of infrared beam breaking per min. Each animal was housed individually in a metabolic cage. Results were averaged separately over the light and dark periods. The measurement was performed during week 6 after testosterone supplementation (N = 4 for each group). Xtot, Ytot, Ztot each denotes movements in X-axis, Y-axis, and Z-axis. (C) Mean respiratory activity recorded as oxygen consumption and carbon dioxide production for animals individually housed in a metabolic cage (N = 4). Results were normalized to total body weight. All results are shown as mean ± SEM, and the difference between control and testosterone groups at each time period was analyzed by t test. ns, not significantly different.