Enhanced physiological tremor deteriorates plantar flexor torque steadiness after bed rest

Area of Science:

• Physiology
• Neuromuscular Function
• Exercise Science

Background:

• Prolonged bed rest leads to significant loss of muscle function and control.
• Maintaining submaximal torque steadiness is crucial for daily activities and athletic performance.
• The impact of bed rest on neuromuscular control, particularly torque fluctuations, requires further investigation.

Purpose of the Study:

• To evaluate the effectiveness of resistance training (RT) in preserving submaximal plantar flexor (PF) torque steadiness after 60 days of bed rest (BR).
• To investigate the changes in torque fluctuations and neuromuscular parameters following BR with and without RT.

Main Methods:

• Twenty-two healthy males were divided into bed rest only (CTR) and bed rest plus resistance training (RT) groups.
• Submaximal isometric PF contractions (20-80% maximum) were assessed for torque fluctuations (coefficient of variation, CV) before and after BR.
• Spectral analysis of torque fluctuations and H-reflex amplitude were measured.

Main Results:

• Torque fluctuations (CV) significantly increased after BR in the CTR group but were attenuated in the RT group.
• A shift towards increased rhythmic activity (6.5-20Hz) in torque fluctuations was observed in the CTR group only.
• H-reflex amplitude decreased in both groups, but this did not correlate with torque fluctuations.

Conclusions:

• Increased torque fluctuations after bed rest are linked to enhanced physiological tremor.
• Resistance training effectively prevented the spectral shift in torque fluctuations and preserved muscle performance.
• RT offsets approximately 50% of the performance decline associated with long-term bed rest.