Testosterone and Resistance Training Improve Muscle Quality in Spinal Cord Injury

Purpose Spinal cord injury (SCI) negatively impacts muscle quality and testosterone levels. Resistance training (RT) has been shown to increase muscle cross-sectional area (CSA) after SCI, whereas testosterone replacement therapy (TRT) has been shown to improve muscle quality in other populations. The purpose of this pilot study was to examine if the combined effects of these interventions, TRT + RT, may maximize the beneficial effects on muscle quality after SCI. Methods Twenty-two SCI subjects randomized into either a TRT + RT (n = 11) or TRT (n = 11) intervention for 16 wk. Muscle quality measured by peak torque (PT) at speeds of 0 degrees center dot s(-1) (PT-0 degrees), 60 degrees center dot s(-1) (PT-60 degrees), 90 degrees center dot s(-1) (PT-90 degrees), and 180 degrees center dot s(-1) (PT-180 degrees), knee extensor CSA, specific tension, and contractile speed (rise time [RTi], and half-time to relaxation [1/2TiR]) was assessed for each limb at baseline and postintervention using 2 x 2 mixed models. Results After 16 wk, subjects in the TRT + RT group increased PT-0 degrees (48.4%, P = 0.017), knee extensor CSA (30.8%, P < 0.0001), and RTi (17.7%, P = 0.012); with no significant changes observed in the TRT group. Regardless of the intervention, changes to PT-60 degrees (28.4%, P = 0.020), PT-90 degrees (26.1%, P = 0.055), and PT-180 degrees (20.6%, P = 0.09) for each group were similar. Conclusions The addition of mechanical stress via RT to TRT maximizes improvements to muscle quality after complete SCI when compared with TRT administered alone. Our evidence shows that this intervention increases muscle size and strength while also improving muscle contractile properties.