The effect of bed rest, unilateral limb immobilization and head‐down tilt on muscle protein synthesis: A systematic review and meta‐analysis

Prokopidis, Konstantinos ORCID: https://orcid.org/0000-0002-6264-9388, Morgan, Paul T ORCID: https://orcid.org/0000-0001-7254-4507, Deane, Colleen S ORCID: https://orcid.org/0000-0002-2281-6479, Witard, Oliver C ORCID: https://orcid.org/0000-0002-5875-8397 and Church, David D (2025) The effect of bed rest, unilateral limb immobilization and head‐down tilt on muscle protein synthesis: A systematic review and meta‐analysis. Experimental Physiology. ISSN 0958-0670

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Abstract

Muscle disuse leads to muscle atrophy and a decrease in muscle function that is primarily driven by reduced muscle protein synthesis (MPS). The aim of this systematic review and meta‐analysis was to examine the effect of different models of muscle disuse on rates of MPS. A literature search was conducted in PubMed, Web of Science, Scopus and Cochrane Library. Eligible randomized and non‐randomized controlled trials compared the effect of bed rest (BR), unilateral lower limb immobilization (ULLI), and 6° head‐down tilt (HDT) on pre–post muscle disuse changes in MPS in adults. Using the random and fixed effects inverse‐variance model, we calculated the mean difference (MD) in the effect of BR on mixed MPS and ULLI on myofibrillar MPS (MyoPS) (both expressed as fractional synthetic rate,%/h). The effect of HDT on MPS was examined through a narrative synthesis of data. A total of 16 studies were included in the systematic review and 13 in the meta‐analysis. A significant reduction in mixed MPS was observed after BR (k = 4; MD: −0.017%/h, 95% CI: −0.023 to −0.011, I2 = 24%, P < 0.01) and a significant reduction in MyoPS was observed after ULLI (k = 9; MD: −0.015%/h, 95% CI: −0.021 to −0.008, I2 = 94%, P < 0.01). HDT led to reductions in both mixed MPS and MyoPS. A comparable reduction in mixed MPS and MyoPS was observed between different models of muscle disuse.