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Strength training counteracts motor performance losses during bed rest.
Minoru Shinohara1, Yasuhide Yoshitake, Motoki Kouzaki
1Dept. of Integrative Physiology, Univ. of Colorado, Boulder, CO 80309-0354, USA. shinohara@colorado.edu
Journal of Applied Physiology (Bethesda, Md. : 1985)
|July 2, 2003
Summary
Bed rest increases muscle torque fluctuations, impacting performance. Strength training effectively counteracts these effects, preserving muscle function and activation strategies.
Area of Science:
- Exercise Physiology
- Muscle Physiology
- Neuromuscular Adaptation
Background:
- Prolonged inactivity, such as bed rest, leads to deconditioning and loss of muscle function.
- Understanding the impact of bed rest on muscle control and the efficacy of countermeasures is crucial for rehabilitation and maintaining physical health.
Purpose of the Study:
- To investigate the effects of a 20-day bed rest period on torque fluctuations and muscle activation strategies.
- To compare the impact of bed rest alone versus bed rest combined with strength training on these parameters.
Main Methods:
- Twelve young men underwent a 20-day bed rest protocol, divided into a control (BRCon) and a strength-training (BRTr) group.
- Training involved dynamic calf-raise and leg-press exercises.
- Maximal and submaximal isometric contractions of ankle and knee extensors were assessed before and after bed rest, measuring torque and electromyogram (EMG) activity.
Main Results:
- Maximal torque decreased significantly in the non-training group for both ankle (9%) and knee extensors (16%), but not in the training group.
- Torque fluctuations, measured by the coefficient of variation (CV), increased significantly in both groups for ankle extensors, with a greater increase in BRCon (88%) than BRTr (41%).
- Knee extensor torque fluctuations increased only in BRCon (22%), correlating with greater EMG changes in medial gastrocnemius and vastus lateralis muscles.
Conclusions:
- Bed rest exacerbates torque fluctuations during submaximal contractions, indicating impaired motor control.
- Strength training effectively mitigates these performance declines and preserves muscle activation patterns.
- The study highlights that alterations in muscle activation following bed rest contribute to increased motor output variability, but strength training can prevent this.