Ground reaction forces during treadmill running in microgravity

Area of Science:

• Space medicine
• Exercise physiology
• Biomechanics

Background:

• Long-duration space missions pose risks to astronaut health, including bone and muscle loss.
• Treadmill exercise with harness systems is used to mitigate these effects in microgravity.
• Reduced gravity-replacement forces during in-flight exercise may alter biomechanical responses compared to Earth-based exercise.

Purpose of the Study:

• To investigate the impact of reduced gravity-replacement forces on ground-reaction forces during astronaut treadmill exercise.
• To compare in-flight (0G) ground-reaction forces with pre-flight (1G) measurements.
• To identify strategies for optimizing exercise effectiveness in microgravity.

Main Methods:

• Seven astronauts completed pre-flight (1G) and in-flight (0G) sessions on an instrumented treadmill.
• Ground-reaction forces were measured during running at speeds of 8.0 kph and greater.
• Varying gravity-replacement forces were applied during in-flight testing.

Main Results:

• In-flight ground-reaction forces were lower than pre-flight forces at equivalent speeds, dependent on gravity-replacement force.
• Ground-reaction forces increased with higher running speeds and greater gravity-replacement forces in microgravity.
• Loading rates achieved during 1G running could not be replicated in 0G.

Conclusions:

• Current gravity-replacement systems have limitations in the magnitude of force they can deliver.
• Increasing running speed during microgravity treadmill exercise is recommended to enhance mechanical loading.
• Optimizing exercise parameters may improve the efficiency of countermeasures for spaceflight-induced deconditioning.