MECHANOSENSITIVITY MAY BE ENHANCED IN SKELETAL MUSCLES OF SPINAL CORD–INJURED VERSUS ABLE-BODIED MEN

Muscle Nerve, 2014 · DOI: 10.1002/mus.24248 · Published: October 1, 2014

Spinal Cord Injury Physiology Rehabilitation

Simple Explanation

This study investigates how muscles respond to exercise in individuals with spinal cord injuries (SCI) compared to able-bodied (AB) individuals. The researchers used neuromuscular electrical stimulation-induced resistance exercise (NMES-RE) to induce muscle contractions and then examined various signaling pathways related to muscle growth. The key finding is that SCI muscles appear to be more sensitive to these contractions, even years after the injury. This heightened sensitivity might be a compensatory mechanism to counteract muscle atrophy commonly seen in SCI. The study also explored specific proteins involved in muscle growth and mechanosensitivity, such as FAK and α7-integrin, finding increased levels in SCI muscles. These proteins play a role in converting mechanical stimuli into anabolic signaling, potentially explaining the enhanced muscle response in SCI individuals.

Study Duration

Not specified

Participants

8 SCI men and 9 AB men

Evidence Level

Not specified

Key Findings

1
SCI muscle appears to be more sensitive to muscle contraction even several years after the injury, possibly due to heightened compensatory mechanisms against muscle atrophy.
2
SCI subjects showed higher phosphorylation states of FAK (Tyr397) at all time points, indicating increased mechanosensitivity compared to AB subjects.
3
SCI individuals exhibited elevated RPS6 phosphorylation 60 minutes post-NMES-RE, suggesting a more robust translation initiation response compared to AB individuals.

Research Summary

The study investigated the effects of neuromuscular electrical stimulation–induced resistance exercise (NMES-RE) on intracellular signaling pathways involved in translation initiation and mechanical loading–induced muscle hypertrophy in spinal cord–injured (SCI) versus able-bodied (AB) individuals. The primary finding is that SCI muscle appears to be highly sensitive to muscle contraction even 22 years after the injury, and it may be more sensitive to mechanical stress than AB muscle, as indicated by higher FAK phosphorylation and α7-integrin levels. The study suggests that heightened signaling associated with muscle mechanosensitivity and translation initiation in SCI muscle may be an attempted compensatory response to offset elevated protein degradation in atrophied SCI muscle.

Practical Implications

Rehabilitation Strategies

NMES-RE can be effectively used to promote muscle hypertrophy in SCI individuals, improving metabolic health.

Targeted Therapies

Understanding the enhanced mechanosensitivity in SCI muscle can lead to the development of targeted therapies to combat muscle atrophy.

Compensatory Mechanisms

Further research into the compensatory mechanisms in SCI muscle may reveal novel therapeutic targets for muscle preservation.

Study Limitations

1
Limited sample size (8 SCI and 9 AB men).
2
Analyses limited by remaining lysate availability.
3
Isometric contractions may not fully represent dynamic, real-world muscle activity.

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