Effects of Use and Disuse on Non-paralyzed and Paralyzed Skeletal Muscles

Aging and Disease, 2016 · DOI: http://dx.doi.org/10.14336/AD.2015.0826 · Published: February 1, 2016

Simple Explanation

Skeletal muscle is critical for physical activity and overall health, impacting aging and body composition. Understanding how muscle responds to use and disuse is important for rehabilitation and prevention of age-related diseases. Voluntary muscle activity is best, but neuromuscular electrical stimulation (NMES) can help paralyzed individuals. Maintaining a healthy muscle-to-fat ratio is important for preventing cardiovascular and metabolic diseases. This paper reviews skeletal muscle strength, effects of deactivation on muscle size and mechanics, body composition changes with atrophy, and the role of voluntary and induced exercise in reversing muscle disuse.

Study Duration

Not specified

Participants

Not specified

Evidence Level

Review Article

Key Findings

1
Muscle size and strength decrease with disuse due to decreased protein synthesis and increased protein breakdown, leading to muscle atrophy and weakness, which can be exacerbated by conditions like stroke and spinal cord injury (SCI).
2
Muscle fiber types can shift from slow-twitch (type I) to fast-twitch (type II) fibers with paralysis, while aging may cause the opposite shift. This fiber type transformation impacts muscle function and metabolism.
3
Electrical stimulation (NMES) and resistance training can help counteract muscle atrophy in paralyzed individuals, improving muscle mass, fat mass, bone mineral density, and metabolic profiles.

Research Summary

This review highlights the importance of skeletal muscle health for overall well-being and physical function, especially in the context of aging and neurological conditions like stroke and spinal cord injury (SCI). Muscle disuse leads to atrophy, changes in fiber type composition, and metabolic imbalances, increasing the risk of cardiovascular and metabolic diseases. These effects are particularly pronounced in individuals with paralysis. Exercise, including electrical stimulation, is a viable countermeasure to mitigate muscle atrophy and improve body composition and metabolic profiles, emphasizing the need for alternative methods to maintain muscle health in cases of limited voluntary movement.

Practical Implications

Rehabilitation Strategies

Healthcare professionals can use this information to design effective rehabilitation programs that prioritize muscle health and function.

NMES Application

NMES can be utilized as a therapeutic intervention to combat muscle atrophy and improve metabolic outcomes in individuals with paralysis.

Lifestyle Interventions

Promoting physical activity and exercise can help maintain muscle mass and prevent age-related muscle loss and associated health risks.

Study Limitations

1
Limited human studies directly comparing specific tension across different aging groups accounting for muscle activation.
2
Varied results in studies examining muscle fiber type transformations after stroke and SCI.
3
Unclear long-term effects of FES-LEC on bone mineral density and the need for continuous physical activity to maintain benefits.

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