Low-dose testosterone replacement therapy and electrically evoked resistance training enhance muscle quality after spinal cord injury

Neural Regeneration Research, 2021 · DOI: https://doi.org/10.4103/1673-5374.303026 · Published: August 1, 2021

Spinal Cord Injury Endocrinology Neurology

Simple Explanation

This study explores the benefits of combining low-dose testosterone replacement therapy (TRT) with electrically evoked resistance training (RT) for individuals with spinal cord injury (SCI). The approach aims to counteract the negative effects of SCI on body composition and cardio-metabolic profiles. The combined effects of TRT and exercise have not been clearly studied, particularly in the SCI population. This perspective summarizes the findings and future implications of a recent investigation that explores the potential clinical applications of combining electrically evoked neuromuscular electrical stimulation-resistance training (NMES-RT) exercise with low-dose TRT for improving several clinical outcomes of individuals with chronic SCI. A randomized controlled clinical trial investigated the effects of daily low-dose TRT (2–6 mg per day) combined with twice-weekly NMES-RT compared to TRT-only for 16 weeks in men with motor complete SCI. The results showed improvements in muscle mass and metabolic rate.

Study Duration

16 weeks

Participants

Men with motor complete SCI

Evidence Level

Randomized controlled clinical trial

Key Findings

1
The TRT + RT group displayed 30–34% increases in muscle cross sectional area (CSA) of the knee extensors with no significant change observed in the TRT group.
2
Basal metabolic rate increased 14–17% following TRT + RT.
3
TRT + RT demonstrated significant elevation in mitochondrial activity of succinate dehydrogenase, a marker for complex II, as well as of citrate synthase, a validated marker for mitochondrial density.

Research Summary

This paper highlights the significance of adding low-dose testosterone replacement therapy (TRT) to electrically evoked resistance training (RT) for SCI patients. It addresses muscle hypertrophy and possible improvements in cardio-metabolic profile in persons with chronic SCI. A randomized controlled clinical trial was conducted to investigate the effects of daily low-dose TRT (2–6 mg per day) combined with twice-weekly NMES-RT compared to TRT-only for 16 weeks in men with motor complete SCI. The findings suggest that exercise and TRT are associated with improvements in insulin sensitivity and carbohydrate metabolism, which is vitally important considering that 80% of insulin-dependent glucose uptake occurs in skeletal muscle.

Practical Implications

Reduced Pressure Injuries

The application of TRT+RT could benefit untrained muscle groups, such as hip extensors, potentially reducing the prevalence and severity of pressure injuries in wheelchair-bound individuals.

Improved Metabolic Health

Combining TRT and exercise provides beneficial changes in metabolic health, mitochondrial health, and function in the SCI population.

Fiber Type Transformation

The study suggests a fiber type shift from fast glycolytic to fast oxidative fibers, improving muscle quality.

Study Limitations

1
The current work is only limited to men with SCI.
2
Women with SCI (20–25% of the SCI population) cannot be enrolled in TRT trials because of ethical considerations.
3
Recruitment of women of SCI is rather challenging to examine gender-based differences on muscle quality in response to exercise.

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