EFFECTS OF TREADMILL TRAINING ON HINDLIMB MUSCLES OF SPINAL CORD–INJURED MICE

Muscle Nerve, 2017 · DOI: 10.1002/mus.25211 · Published: February 1, 2017

Spinal Cord Injury Rehabilitation Musculoskeletal Medicine

Simple Explanation

This study looks at how treadmill training affects muscles in mice after a spinal cord injury. The researchers wanted to know if different lengths of training (3, 6, or 9 weeks) had different effects on muscle size and type. Mice with spinal cord injuries were put on treadmills for different durations, and their muscle tissues were analyzed. The analysis focused on muscle fiber type composition and the size of these fibers. The results showed that longer training (9 weeks) helped prevent muscle shrinking, especially in fast-twitch muscles. However, the training didn't change the type of muscle fibers much. This suggests exercise can help paralyzed limbs after spinal cord injury.

Study Duration

9 weeks

Participants

49 male C57BL/6 mice

Evidence Level

Not specified

Key Findings

1
Muscle fiber type composition did not change with training in SCI animals, indicating limited effects on muscle fiber type composition from treadmill training.
2
Nine weeks of treadmill training increased the cross-sectional area (CSA) of type IIB and IIX fibers in TA and MG muscles, demonstrating a beneficial effect on fast-twitch muscle size with longer training durations.
3
Muscle fiber CSA tended to be smaller in treadmill-trained than untrained animals early in recovery but greater in trained than untrained animals by 10 weeks.

Research Summary

This study investigated the effects of different durations of treadmill training on muscle properties in mice with incomplete spinal cord injury (SCI). The key finding was that 9 weeks of treadmill training was effective in preventing atrophy of fast-twitch muscles, specifically type IIB and IIX fibers in the tibialis anterior (TA) and medial gastrocnemius (MG) muscles. However, the study found limited effects of treadmill training on slow-twitch muscles and muscle fiber type composition, suggesting that other types of interventions or more intense exercise may be needed to influence these muscle characteristics after SCI.

Practical Implications

Rehabilitation Strategies

Longer durations of treadmill training (e.g., 9 weeks) should be considered in rehabilitation programs for individuals with incomplete SCI to maximize the benefits on fast-twitch muscle size and prevent atrophy.

Targeted Interventions

Additional or alternative interventions may be needed to target slow-twitch muscles and muscle fiber type composition in SCI patients, as treadmill training alone may have limited effects on these muscle characteristics.

Timing of Exercise

Initiating intensive exercise such as treadmill training too early after SCI may have a detrimental effect on muscle properties

Study Limitations

1
The study was conducted on mice, and the results may not be directly generalizable to humans.
2
The study focused on incomplete SCI, and the effects of treadmill training may differ in cases of complete SCI.
3
It was sometimes difficult to distinguish type IIX and type IIB fibers, especially in the TA muscle.

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