Changes in lower extremity muscle function after 56 days of bed rest

Area of Science:

• Space physiology
• Skeletal muscle research
• Exercise science

Background:

• Muscle function declines during microgravity and bed rest, impacting spaceflight missions.
• Developing effective countermeasures to prevent muscle loss is crucial for astronaut health.
• Skeletal muscle adaptations to unloading and exercise interventions require detailed study.

Purpose of the Study:

• To evaluate the effectiveness of resistive vibration exercise (RVE) as a countermeasure against muscle function loss during bed rest.
• To assess the impact of RVE on maximal isometric plantar-flexion force (IPFF) and jumping performance.
• To investigate the differential effects of bed rest and RVE on various skeletal muscle functions.

Main Methods:

• 20 male participants underwent 56 days of bed rest.
• Ten participants were randomized to RVE (resistance exercise + whole-body vibration); 10 served as controls.
• Measurements included IPFF, EMG/force ratio, jumping power, and height before and after bed rest, and during early recovery.

Main Results:

• The control group showed significant declines in IPFF (-17.1%), jumping peak power (-24.1%), and height (-28.5%).
• RVE preserved IPFF and mitigated the decline in jumping performance (peak power -12.2%, height -14.2%).
• IPFF decreased in both groups during the first day of reambulation, indicating complex recovery dynamics.

Conclusions:

• Bed rest significantly impairs skeletal muscle strength and power, with varying effects on different muscle functions.
• RVE is effective in maintaining isometric strength but only partially mitigates declines in dynamic jumping performance.
• Further research is needed to develop comprehensive countermeasures that preserve both muscle strength and power during spaceflight and recovery.