Testosterone and Resistance Training Improves Muscle Quality Following Spinal Cord Injury

Abstract

Spinal cord injury (SCI) adversely effects muscle quality and testosterone levels. Following SCI, resistance training (RT) has been shown to increase muscle cross-sectional area (CSA). Testosterone replacement therapy (TRT) in other populations has also been shown to improve muscle quality. PURPOSE: To examine if the combination of RT and TRT (TRT+RT) can maximize the beneficial effects to muscle quality following SCI. METHODS: Twenty-two SCI subjects were randomized into two intervention groups for 16-weeks: TRT+RT (n = 11), or TRT (n = 11). Muscle quality was assessed by measuring peak torque at speeds of 0, 60, 90, and 180°/sec (PT-0°, PT-60°, PT-90°, PT-180°), knee extensor CSA (KE-CSA), specific tension (ST), and contractile speeds (rise time [RTi], and half-time to relaxation [½TiR]) for each limb prior to testing and following the intervention. 2x2 mixed models with subject identifiers added as random effects and post-hoc Tukey-Kramer HSD tests identified pairwise differences within interactions (P < 0.05). RESULTS: Following the intervention period, participants in the TRT+RT group increased PT-0° (48.4%, P = 0.017), KE-CSA (30.8%, P < 0.001), ST (8%, NS), and RTi (17.7%, P = 0.012). PT-0° decreased (17%, NS), KE-CSA slightly increased (10%, NS), ST decreased (20%, NS), and RTi also slightly decreased (9%, NS) in the TRT group. Changes to PT-60°, PT-90°, PT-180°, and ½TiR for each group were similar following the 16-week intervention. CONCLUSION: Mechanical stress induced via RT combined with TRT maximizes enhancements of muscle quality when compared to TRT interventions alone in men with complete SCI. Our study shows that TRT+RT increases both muscle size, strength, and also improves muscle contractile properties.