Short, intermittent episodes of disuse muscle atrophy (DMA) may have negative impact on age related muscle loss. There is evidence of variability in rate of DMA between muscles and over the duration of immobilization. As yet, this is poorly characterized. This review aims to establish and compare the time-course of DMA in immobilized human lower limb muscles in both healthy and critically ill individuals, exploring evidence for an acute phase of DMA and differential rates of atrophy between and muscle groups. MEDLINE, Embase, CINHAL and CENTRAL databases were searched from inception to April 2021 for any study of human lower limb immobilization reporting muscle volume, cross-sectional area (CSA), architecture or lean leg mass over multiple post-immobilization timepoints. Risk of bias was assessed using ROBINS-I. Where possible meta-analysis was performed using a DerSimonian and Laird random effects model with effect sizes reported as mean differences (MD) with 95% confidence intervals (95% CI) at various time-points and a narrative review when meta-analysis was not possible. Twenty-nine studies were included, 12 in healthy volunteers (total n = 140), 18 in patients on an Intensive Therapy Unit (ITU) (total n = 516) and 3 in patients with ankle fracture (total n = 39). The majority of included studies are at moderate risk of bias. Rate of quadriceps atrophy over the first 14 days was significantly greater in the ITU patients (MD −1.01 95% CI −1.32, −0.69), than healthy cohorts (MD −0.12 95% CI −0.49, 0.24) (P < 0.001). Rates of atrophy appeared to vary between muscle groups (greatest in triceps surae (−11.2% day 28), followed by quadriceps (−9.2% day 28), then hamstrings (−6.5% day 28), then foot dorsiflexors (−3.2% day 28)). Rates of atrophy appear to decrease over time in healthy quadriceps (−6.5% day 14 vs. −9.1% day 28) and triceps surae (−7.8% day 14 vs. −11.2% day 28), and ITU quadriceps (−13.2% day 7 vs. −28.2% day 14). There appears to be variability in the rate of DMA between muscle groups, and more rapid atrophy during the earliest period of immobilization, indicating different mechanisms being dominant at different timepoints. Rates of atrophy are greater amongst critically unwell patients. Overall evidence is limited, and existing data has wide variability in the measures reported. Further work is required to fully characterize the time course of DMA in both health and disease.

中文翻译：

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健康与疾病下肢废用性肌肉萎缩的时间进程

短期、间歇性的废用性肌肉萎缩症 (DMA) 可能对与年龄相关的肌肉损失产生负面影响。有证据表明肌肉之间和固定期间的 DMA 速率存在差异。迄今为止，这方面的特征还很差。本综述旨在建立和比较 DMA 在健康人和危重病人的固定人体下肢肌肉中的时程，探索 DMA 急性期的证据以及肌肉群和肌肉群之间的不同萎缩率。从开始到 2021 年 4 月，对 MEDLINE、Embase、CINHAL 和 CENTRAL 数据库进行了搜索，以查找在多个固定后时间点上报告肌肉体积、横截面积 (CSA)、结构或瘦腿质量的任何关于人类下肢固定的研究。使用 ROBINS-I 评估偏倚风险。在可能的情况下，使用 DerSimonian 和 Laird 随机效应模型进行荟萃分析，效应量报告为不同时间点的均值差 (MD) 和 95% 置信区间 (95% CI)，当没有进行荟萃分析时进行叙述性回顾可能的。纳入了 29 项研究，其中 12 项来自健康志愿者（总共n  = 140)，18 例在强化治疗单元 (ITU) 的患者中（总n  = 516），3 例在踝关节骨折患者中（总n  = 39）。大多数纳入的研究都存在中度偏倚风险。ITU 患者 (MD −1.01 95% CI −1.32, −0.69) 的前 14 天股四头肌萎缩率显着高于健康队列 (MD −0.12 95% CI −0.49, 0.24) ( P < 0.001)。肌肉群之间的萎缩率似乎不同（最大的是小腿三头肌（-11.2%，第 28 天），其次是股四头肌（-9.2%，第 28 天），然后是腘绳肌（-6.5%，第 28 天），然后是足背屈肌（-3.2%）第 28 天））。健康股四头肌（第 14 天 -6.5% 对比第 28 天 -9.1%）和小腿三头肌（第 14 天 -7.8% 对比第 28 天 -11.2%）和 ITU 股四头肌（−13.2%第 7 天对比 -28.2% 第 14 天）。肌肉群之间的 DMA 速率似乎存在差异，并且在固定的最早阶段萎缩更快，表明不同的机制在不同的时间点占主导地位。重症患者的萎缩率更高。总体证据有限，现有数据在报告的措施中存在很大差异。