Limited musculoskeletal benefits of artificial gravity combined with cycling during bed rest: Results from the BRACE study.

All three groups experienced thigh fat-free muscle volume loss during 60 days of head-down tilt bed rest, with the control group losing the most.

• Control group lost 10.5% ± 2.6% of thigh fat-free muscle volume.
• Exercise-only group lost 6.9% ± 2.4% of thigh fat-free muscle volume.
• Exercise with artificial gravity group lost 4.3% ± 2.4% of thigh fat-free muscle volume.
• EX-AG showed significantly less atrophy than C (p < 0.001).
• Study involved 24 healthy male participants randomized into three groups (C, EX, EX-AG).

EX-AG preserved more muscle than control in both anterior and posterior compartments, while exercise alone only preserved more muscle anteriorly.

• EX-AG preserved more muscle in the anterior compartment compared with C (p < 0.001).
• EX-AG preserved more muscle in the posterior compartment compared with C (p < 0.05).
• EX preserved more muscle only in the anterior compartment compared with C (p < 0.05).
• Posterior compartment muscle preservation was not significantly different between EX and C.

The fat ratio increased more in the control group compared with EX-AG, but not compared with the exercise-only group.

• Fat ratio increased by 8.9% ± 6.0% in the control group.
• Fat ratio changed by -0.8% ± 3.8% in the EX-AG group.
• Fat ratio increased by 6.5% ± 9.8% in the EX group.
• The difference in fat ratio change between C and EX-AG was significant (p < 0.05), but the difference between C and EX was not significant.

Muscle fat infiltration increased across all groups during bed rest and was not significantly different between groups.

• Intramuscular fat increased by 7.0% ± 3.7% in the control group.
• Intramuscular fat increased by 6.2% ± 4.3% in the exercise-only group.
• Intramuscular fat increased by 3.1% ± 4.7% in the EX-AG group.
• Differences in muscle fat infiltration between groups were not statistically significant (p > 0.05).

Maximal isokinetic torque decreased in all groups across all measured angular velocities and was not significantly different between groups.

• Isokinetic strength was assessed via isokinetic dynamometry.
• Decreases in maximal isokinetic torque were observed across all groups at all measured angular velocities.
• No significant differences in torque changes were found between the C, EX, and EX-AG groups (p > 0.05).
• Neither exercise alone nor exercise combined with artificial gravity provided significant protection of isokinetic strength.

This study is the first to investigate the combination of artificial gravity and exercise as a countermeasure to body composition changes induced by long-term bed rest.

• The study used 60-day 6° head-down tilt bed rest to simulate microgravity-induced deconditioning.
• Assessments included whole-body MRI for muscle volume, intramuscular fat, and body composition, as well as isokinetic dynamometry for strength.
• The countermeasure combined aerobic exercise (cycling) with artificial gravity.
• The study evaluated whether the combination was superior to exercise alone.