Fernandez-Gonzalo Rodrigo, McDonnell Adam C, Simpson Elizabeth J, Macdonald Ian A, Rullman Eric, Mekjavic Igor B
Department of Laboratory Medicine, Division of Clinical Physiology, Karolinska Institutet, and Unit of Clinical Physiology, Karolinska University Hospital, Stockholm, Sweden.
Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Ljubljana, Slovenia.
Front Physiol. 2021 Jul 16;12:676501. doi: 10.3389/fphys.2021.676501. eCollection 2021.
To evaluate the individual responses in skeletal muscle outcomes following bed rest, data from three studies (21-day PlanHab; 10-day FemHab and LunHab) were combined. Subjects ( = 35) participated in three cross-over campaigns within each study: normoxic (NBR) and hypoxic bed rest (HBR), and hypoxic ambulation (HAMB; used as control). Individual variability (SD) was investigated as √(SD -SD ), where SD and SD are the standard deviations of the change score (i.e., post - pre) in the experimental (NBR and HBR) and the control (HAMB) groups, respectively. Repeatability and moderators of the individual variability were explored. Significant SD was detected for knee extension torque, and thigh and calf muscle area, which translated into an individual response ranging from 3 to -17% for knee extension torque, -2 to -12% for calf muscle area, and -1 to -8% for thigh muscle area. Strong correlations were found for changes in NBR vs. HBR (i.e., repeatability) in thigh and calf muscle area ( = 0.65-0.75, < 0.0001). Change-scores in knee extension torque, and thigh and calf muscle area strongly correlated with baseline values ( < 0.001; between -0.5 and -0.9). Orthogonal partial least squares regression analysis explored if changes in the investigated variables could predict calf muscle area alterations. This analysis indicated that 43% of the variance in calf muscle area could be attributed to changes in all of the other variables. This is the first study using a validated methodology to report clinically relevant individual variability after bed rest in knee extension torque, calf muscle area, and (to a lower extent) thigh muscle area. Baseline values emerged as a moderator of the individual response, and a global bed rest signature served as a moderately strong predictor of the individual variation in calf muscle area alterations.
为评估卧床休息后骨骼肌指标的个体反应，合并了三项研究（21天的PlanHab；10天的FemHab和LunHab）的数据。受试者（n = 35）在每项研究中参与了三个交叉试验阶段：常氧卧床休息（NBR）、低氧卧床休息（HBR）以及低氧行走（HAMB；用作对照）。个体变异性（SD）通过√(SD₂ - SD₁)来研究，其中SD₂和SD₁分别是实验组（NBR和HBR）和对照组（HAMB）中变化分数（即，后测 - 前测）的标准差。探索了个体变异性的重复性和调节因素。在膝关节伸展扭矩以及大腿和小腿肌肉面积方面检测到显著的SD，这转化为膝关节伸展扭矩的个体反应范围为3%至 - 17%，小腿肌肉面积为 - 2%至 - 12%，大腿肌肉面积为 - 1%至 - 8%。在大腿和小腿肌肉面积方面，发现NBR与HBR之间的变化（即重复性）具有强相关性（r = 0.65 - 0.75，P < 0.0001）。膝关节伸展扭矩以及大腿和小腿肌肉面积的变化分数与基线值密切相关（P < 0.001；r在 - 0.5至 - 0.9之间）。正交偏最小二乘回归分析探讨了所研究变量的变化是否能够预测小腿肌肉面积的改变。该分析表明，小腿肌肉面积43%的方差可归因于所有其他变量的变化。这是第一项使用经过验证的方法来报告卧床休息后膝关节伸展扭矩、小腿肌肉面积以及（程度较低的）大腿肌肉面积方面临床相关个体变异性的研究。基线值成为个体反应的调节因素，而一个整体的卧床休息特征作为小腿肌肉面积改变个体差异的中等强度预测指标。
