2023 Volume 1 Article ID: 85
Purpose: Microgravity leads to muscle atrophy, especially in antigravity muscles including the psoas muscle (PM). The hybrid training system (HTS) is a method that uses the electrically stimulated eccentric contraction of the antagonist muscle as the exercise resistance of the agonist muscle. The purpose of this study was to examine the effects of HTS on PM. Methods: We investigated the HTS (9 legs) and control (CON) (9 legs) sides. Stimulation electrodes were attached to the gluteus maximus muscle of the HTS side, and electrical stimulation was applied during hip flexion. The CON side performed the same exercise without electrical stimulation. The exercise task was hip flexion from a stationary standing position,10 sets of 10 repetitions per set, 3 times/week for 6 weeks. The comparison of PM volume and muscle strength before and after training was made by using the Wilcoxon signed-rank test. Results: The volume of PM on the HTS side significantly increased (pre: 352.73 ± 33.84, post: 365.90 ± 40.07 cm3) (P<0.01). The hip flexor strength on the HTS side significantly increased (pre: 203.89 ± 41.98, post: 230.22 ± 25.67 N) (P<0.05). There was no significant increase on CON side. Conclusions: HTS increased the strength and muscle volume of the agonist when the antagonist electrically was stimulated.
