Functional and structural adaptations of skeletal muscle to microgravity

Area of Science:

• Space Medicine
• Skeletal Muscle Physiology
• Exercise Physiology

Background:

• Space travel presents unique physiological challenges to the human body.
• Skeletal muscle is particularly susceptible to the effects of microgravity.
• Understanding these effects is crucial for astronaut health and mission success.

Purpose of the Study:

• To summarize the major effects of space travel on skeletal muscle.
• To emphasize factors that alter muscle function during spaceflight.
• To review changes in muscle mass, force, power, and substrate utilization.

Main Methods:

• Review of studies on rats and humans exposed to microgravity.
• Analysis of muscle mass changes, fiber type susceptibility, and force production.
• Examination of alterations in muscle shortening velocity and substrate metabolism.

Main Results:

• Rapid muscle atrophy observed in both rats and humans, with antigravity muscles disproportionately affected.
• Significant decline in peak force and power, attributed to muscle atrophy and contractile protein loss.
• Increased shortening velocity and altered substrate utilization (reduced fat oxidation, increased glycogen use) leading to increased fatigue.
• Increased susceptibility to eccentric contraction-induced damage upon return to Earth.

Conclusions:

• Space travel induces profound deleterious changes in skeletal muscle.
• Muscle atrophy, reduced force and power, and altered metabolism are key findings.
• Further research is needed to understand the mechanisms and develop countermeasures for muscle deconditioning during spaceflight.