PURPOSE Short periods of limb immobilization lower myofibrillar protein synthesis rates. Within skeletal muscle, the extracellular matrix of connective proteins is recognized as an important factor determining the capacity to transmit contractile force. Little is known regarding the impact of immobilization and subsequent recovery on muscle connective protein synthesis rates. This study examined the impact of one week of leg immobilization and two weeks of subsequent ambulant recovery on daily muscle connective protein synthesis rates. METHODS Thirty healthy, young (24 ± 5 y) men were subjected to 7 days of one-legged knee immobilization followed by 14 days of ambulant recovery. Deuterium oxide ingestion was applied over the entire period and muscle biopsy samples were collected before immobilization, after immobilization, and after recovery to measure muscle connective protein synthesis rates and mRNA expression of key extracellular matrix proteins (collagen I, collagen III), glycoproteins (fibronectin, tenascin-C), and proteoglycans (fibromodulin, and decorin). A two-way repeated measures (time x leg) ANOVA was used to compare changes in muscle connective protein synthesis rates during immobilization and recovery. RESULTS During immobilization, muscle connective protein synthesis rates were lower in the immobilized (1.07 ± 0.30 %/d) compared with the non-immobilized (1.48 ± 0.44 %/d; P < 0.01) leg. When compared to the immobilization period, connective protein synthesis rates in the immobilized leg increased during subsequent recovery (1.48 ± 0.64 %/d; P < 0.01). Following recovery, skeletal muscle collagen I, collagen III, fibronectin, fibromodulin, and decorin mRNA expression increased when compared to the post-immobilization timepoint (all P < 0.001). CONCLUSIONS One week of leg immobilization lowers muscle connective protein synthesis rates. Muscle connective protein synthesis rates increase during subsequent ambulant recovery, which is accompanied by increased mRNA expression of key extracellular matrix proteins.

中文翻译：

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单腿固定一周会降低健康年轻人的肌肉结缔蛋白合成率。

目的 短期肢体固定会降低肌原纤维蛋白合成率。在骨骼肌内，结缔蛋白的细胞外基质被认为是决定传递收缩力能力的重要因素。关于固定和随后的恢复对肌肉结缔蛋白合成率的影响知之甚少。这项研究考察了腿部固定一周和随后两周的移动恢复对每日肌肉结缔蛋白合成率的影响。方法 30 名健康年轻（24 ± 5 岁）男性接受 7 天的单腿膝关节固定，随后进行 14 天的流动康复。整个期间均摄入氧化氘，并在固定前、固定后和恢复后收集肌肉活检样本，以测量肌肉结缔蛋白合成率和关键细胞外基质蛋白（胶原蛋白 I、胶原蛋白 III）、糖蛋白（纤连蛋白）的 mRNA 表达。 、生腱蛋白-C) 和蛋白聚糖（纤维调节蛋白和核心蛋白聚糖）。使用双向重复测量（时间 x 腿）方差分析来比较固定和恢复期间肌肉结缔蛋白合成率的变化。结果 固定期间，固定腿的肌肉结缔蛋白合成率 (1.07 ± 0.30 %/d) 低于非固定腿 (1.48 ± 0.44 %/d；P < 0.01)。与固定期相比，固定腿的结缔蛋白合成率在随后的恢复过程中有所增加（1.48 ± 0.64 %/d；P < 0.01）。恢复后，与固定后时间点相比，骨骼肌胶原蛋白 I、胶原蛋白 III、纤连蛋白、纤维调节蛋白和核心蛋白聚糖 mRNA 表达增加（所有 P < 0.001）。结论 腿部固定一周会降低肌肉结缔蛋白合成率。在随后的移动恢复过程中，肌肉结缔蛋白合成率增加，同时关键细胞外基质蛋白的 mRNA 表达增加。