Exercise Responses to Gravity-Independent Flywheel Aerobic and Resistance Training

Area of Science:

• Space physiology
• Exercise science
• Biomedical engineering

Background:

• Microgravity causes physiological deconditioning, impacting astronaut health.
• Existing exercise systems have limitations for long-duration spaceflight.
• Novel exercise devices are needed to meet mass and volume constraints for deep space missions.

Purpose of the Study:

• To evaluate the efficacy of the gravity-independent Multi-Mode Exercise Device (M-MED).
• To assess the M-MED's capacity for both resistance exercise (RE) and aerobic exercise (AE) stimuli.
• To determine the M-MED's potential as a countermeasure for spaceflight-induced deconditioning.

Main Methods:

• Eight men and nine women (mean age 22.0 ± 0.4 yr) underwent 5 weeks of M-MED training.
• Training included 2 days/week of RE (squats) and 3 days/week of AE (rowing at ~90% Vo2max).
• Pre- and post-training assessments included aerobic capacity, MRI, strength tests, and muscle biopsies.

Main Results:

• Significant improvements observed in VO2max (8%), 3RM strength (18%), and quadriceps femoris cross-sectional area (CSA) (10%).
• Increased knee extensor strength and fatigue resistance.
• Muscle biopsies showed increased myofiber CSA, citrate synthase activity, RNA concentration, and specific mRNA expressions (IGF-I, Type IIa MHC), with decreased Type IIx MHC mRNA.

Conclusions:

• A low volume of M-MED exercise induces substantial adaptations in cardiovascular and musculoskeletal systems.
• The M-MED demonstrates potential for diverse countermeasure exercises.
• Further testing in ground-based spaceflight simulations is recommended.