Foot forces during exercise on the International Space Station

Area of Science:

• Space medicine
• Human physiology
• Biomechanical engineering

Background:

• Long-duration spaceflight causes detrimental musculoskeletal effects.
• Existing exercise countermeasures on the International Space Station (ISS) have limitations.
• Previous research indicates exercise devices may not provide sufficient loading.

Purpose of the Study:

• To quantify the mechanical loads generated by ISS exercise devices.
• To compare on-orbit loads with terrestrial exercise.
• To assess the efficacy of current countermeasures for maintaining musculoskeletal health.

Main Methods:

• In-shoe force measurements were conducted on four male astronauts during ISS missions.
• Data collected during maximal load activities on treadmill with vibration isolation and stabilization (TVIS), cycle ergometer with vibration isolation and stabilization (CEVIS), and interim resistance exercise device (iRED).
• Comparison with on-orbit and Earth-based exercise data.

Main Results:

• Maximum single-leg loads on TVIS reached 1.77 body weight (BW) during running.
• Resistance exercise yielded maximum single-leg forces of 0.72 BW (heel raises) and 0.68 BW (squats).
• CEVIS generated minimal forces (0.19 BW). Loads were significantly lower than Earth-based exercise, except for maximal CEVIS settings.

Conclusions:

• Current ISS exercise devices, including TVIS, CEVIS, and iRED, generate lower mechanical loads than comparable Earth exercises.
• Significant decrements in loading were observed for walking (77%), running (75%), and squats (65%).
• Future countermeasures require improved harnesses for higher loads and greater resistance capabilities to mitigate spaceflight-induced musculoskeletal decline.