Flywheel resistance exercise to maintain muscle oxidative potential during unloading

Area of Science:

• Exercise Physiology
• Space Medicine
• Skeletal Muscle Metabolism

Background:

• Spaceflight leads to reduced skeletal muscle oxidative and aerobic capacity.
• Unilateral lower limb unloading (UL) is a model to study these effects.
• Resistance exercise (RE) may mitigate these metabolic changes.

Purpose of the Study:

• To assess the efficacy of RE in counteracting muscle metabolic perturbations induced by 5 weeks of UL.
• To investigate the impact of RE on key gene expression related to muscle oxidative and glycolytic capacity.

Main Methods:

• 21 participants underwent 5 weeks of UL, with one group performing concurrent RE (UL+RE) and a control group (UL).
• RE involved iso-inertial knee extensions (4 sets of 7 reps, 2-3 times/week).
• Muscle biopsies analyzed mRNA expression of PGC-1alpha, VEGF, PFK, and glycogen-related enzymes.

Main Results:

• Unloading (Grp UL) decreased PGC-1alpha expression by 36% and increased PFK expression 1.5-fold.
• A trend towards decreased VEGF was observed in the UL group.
• The UL+RE group showed no significant changes in these metabolic markers.

Conclusions:

• Five weeks of unloading reduces skeletal muscle oxidative capacity and increases glycolytic enzyme activity.
• A concise regimen of 12 high-force, low-volume RE sessions effectively attenuated these unloading-induced metabolic alterations.
• This RE strategy may preserve skeletal muscle integrity and endurance, supporting astronaut health during spaceflight.