Do females and males exhibit a similar sarcopenic response as a consequence of normoxic and hypoxic bed rest?

Abstract

This study investigated the effects of hypoxia on the known processes of adaptation of body composition and muscle function to normoxic inactivity. Females (n = 12) and males (n = 11) took part in the following interventions: hypoxic ambulation (HAMB; ∼4000 m); hypoxic bed rest (HBR; ∼4000 m) and normoxic bed rest (NBR). Prior to and immediately following each intervention, body composition, thigh and lower leg crosssectional area (CSA) and isometric muscular strength were recorded. Participants lost body mass (HAMB: male −1.5 ± 0.9 kg, female −1.9 ± 0.7 kg; HBR: male −2.0 ± 1.8 kg, female −2.4 ± 0.8 kg; NBR: male −1.4 ± 1.3 kg, female −1.4 ± 0.9 kg) and lean mass (HAMB: male −3.9 ± 3.0%, female −3.4 ± 2.0%; HBR: male −4.0 ± 4.4%, female −4.1 ± 2.0%; NBR: male −4.0 ± 3.4%, female −2.2 ± 2.7%) with no between-condition or sex differences. Knee extension decreased for males in NBR compared to HAMB (HAMB: male −0.2 ± 9.1%, female 1.3 ± 4.9%; HBR: male −7.8 ± 10.3%, female −3.3 ± 10.9%; NBR: male −14.5 ± 11%, female −3.4 ± 6.9%). Loss of force during maximal voluntary contraction (MVC) in the knee extensors was significantly different between males and females following NBR. There were no other significant changes noted following the experimental interventions. There were no differences recorded between sexes in maximal MVC for elbow or ankle joints. Female lower leg CSA decreased following bed rest (HAMB:-4.5 ± 2.0%; HBR:-9.9 ± 2.6%; NBR:-8.0 ± 1.6%). These findings indicate that a 10-day hypoxic bed rest does not exert any significant additional effect on muscle atrophy when compared to NBR, except for female thigh CSA. In contrast to males, who exhibited a significant loss of muscle strength, no such decrement in strength was observed in the female participants.

Adaptation to full weight‐bearing following disuse in rats: The impact of biological sex on musculoskeletal recovery

“…Indeed, force and endurance measurements performed in healthy participants (Clark et al., 2003 ; Fulco et al., 1999 ; Maughan et al., 1986 ; Russ & Kent‐Braun, 2003 ), and following limb immobilization (Semmler et al., 1999 ), repeatedly highlight that women have greater endurance capacity for isometric and dynamic muscle contractions compared to men. While functional decrements, as compared to simple force production, following unloading are sometimes observed to a greater extent in women (Deschenes et al., 2009 ; Wu et al., 2022 ; Yasuda et al., 2005 ), it is not always the case (de Carvalho et al., 2022 ; Mekjavic et al., 2021 ; Miles et al., 2005 ). In our animals, we observed greater improvement in muscle function after 7 days of recovery at full weight‐bearing in females than in males, and studies performed in humans have found similar results in participants recovering from immobilization (Semmler et al., 1999 ) and muscle exhaustion (Fulco et al., 1999 ).…”

Substantial and Reproducible Individual Variability in Skeletal Muscle Outcomes in the Cross-Over Designed Planica Bed Rest Program

“…In addition, information regarding nutritional status (i.e., change score and CV of actual vs. targeted energy intake; Supplementary Table 2) was collected for the three studies. Results for some of these outcomes from each individual study have been published elsewhere (Debevec et al, 2014;McDonnell et al, 2019McDonnell et al, , 2020Mekjavic et al, 2020).…”

Case Report: Muscle Wasting during Severe Sustained Hypoxia in Two Professional Mountaineers

“…Regardless of the level of oxygen, men and women show sex-dependent differences in their muscle tissue composition (31). Compared with normoxic bed rest, hypoxic bed rest led to larger reductions of thigh cross-sectional area in females than in males (32). Besides sex-dependent muscle tissue differences, metabolic differences at altitude between women and men should be considered.…”