Abstract
The present study aims to investigate the effects of 8 weeks of bed rest, with or without resistance exercise intervention, on the volumes of muscle tissue and the intramuscular, intermuscular, and subcutaneous adipose tissues of the thigh. Twenty men were included, who were randomly assigned in three groups: resistance exercises group (RE group), resistance exercises with whole‐body vibration group (VRE group), and nonexercise control group (CTR group). The RE and VRE groups performed resistance exercises during 8 weeks of bed rest (3 days per week). Additionally, consecutive axial magnetic resonance images were obtained before and after the bed rest. Using these images, the volumes of the muscle tissue and the intramuscular adipose tissue, intermuscular adipose tissue, and subcutaneous adipose tissue of the thigh were evaluated. No significant time‐by‐group interaction was observed the volumes of the muscle tissue and the intramuscular adipose tissue, intermuscular adipose tissue, and subcutaneous adipose tissue between the RE and VRE groups. Furthermore, the RE and VRE groups were pooled as the resistance exercise intervention group (TR group), wherein their thigh muscle tissue volume was observed to be maintained after the bed rest. However, that of the CTR group significantly decreased. Regarding the thigh intramuscular adipose tissue and intermuscular adipose tissue volumes, no significant difference was observed among the CTR and TR groups. Although subcutaneous adipose tissue volume in the CTR group significantly increased after the bed rest, no changes were observed in that of the TR group. Therefore, the results of the present study suggested that within the 8 weeks of bed rest, adipose tissue adaptation differs depending on the location
Highlights
IntroductionMany attempts have been made to evaluate the effect of prolonged bed rest (considered as the best physical inactivity model) on human deconditioning, such as muscle atrophy (Akima et al, 2000; Belavý et al, 2009; Pavy-Le Traon et al, 2007) and adipose tissue accumulation (Belavý et al, 2014; Krebset al., 1990)
Many attempts have been made to evaluate the effect of prolonged bed rest on human deconditioning, such as muscle atrophy (Akima et al, 2000; Belavý et al, 2009; Pavy-Le Traon et al, 2007) and adipose tissue accumulation (Belavý et al, 2014; Krebset al., 1990)
The results of the present study suggested that within the 8 weeks of bed rest, adipose tissue adaptation differs depending on the location disuse, intermuscular adipose tissue, intramuscular fat, muscle atrophy, resistance training, unloading model
Summary
Many attempts have been made to evaluate the effect of prolonged bed rest (considered as the best physical inactivity model) on human deconditioning, such as muscle atrophy (Akima et al, 2000; Belavý et al, 2009; Pavy-Le Traon et al, 2007) and adipose tissue accumulation (Belavý et al, 2014; Krebset al., 1990). Belavý et al (2009) reported that the volumes of the knee extensors, knee flexors, and adductor muscles decreased by 14%, 11%, and 5%, respectively, as a result of 8 weeks of bed rest They detailed the atrophic response of the individual muscles on each muscle group in the thigh. A similar result had been shown in the study of Akima et al (2000), wherein a variation in the relative volume change of individual muscles in the knee extensors and knee flexors ranged from −8% to −5% and −15% to −5%, respectively, after 20 days of bed rest. Increases in the relaxation time of the muscle T2 have been known to indicate increased in that of the intramuscular adipose tissue2000 Since this finding is not well supported in the literature, a more detailed image analysis is needed to segment the muscle and adipose tissues
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