Healthcare · Oct 15, 2026

Cardiorespiratory Fitness Decline After Short-Term Experimental Bed Rest in Older Adults and Ageing-Focused Cohorts Aged 55-65 Years: A Systematic Review

By Vega-Fernández G, Valenzuela-Fuenzalida JJ, Jeria-Pizarro Y et al.

Background/Objectives: Short-term bed rest may reduce cardiorespiratory capacity for mobility and rehabilitation, but gas-exchange-assessed fitness has not been synthesised in older adults. We characterised immediate V.O2peak/V.O2max change, recovery, and countermeasures. Methods: This PROSPERO-registered review (CRD420261431685) searched seven databases and two trial registries through 24 May 2026, with Embase and SPORTDiscus through 26 May. Eligible studies imposed 5-14 days of horizontal bed rest (HBR) or 6° head-down tilt bed rest (HDBR) in cohorts with mean age ≥ 60 years or ageing-focused programmes enrolling adults aged 55-65 years. Reports sharing participants and protocol formed one cohort/protocol unit. Body-mass-normalised V.O2 was primary; absolute V.O2 was separate. Risk of bias was assessed with RoB 2 or the revised JBI tool, and certainty with GRADE. Meta-analysis was not undertaken because three independent, comparable effects were unavailable. Results: Of 1964 records, 15 reports formed six units representing four to six independent participant groups. Across four HBR units (n = 9-19), V.O2peak/V.O2max declined by 4.9-15.3%; two percentages were directly reported, one was calculated from a reported change, and one from unit-adjudicated means (low certainty for direction; very low for magnitude). In one HDBR trial, changes were -13.4% ± 12.5% SD in controls (n = 9) and -3.5% ± 5.2% SD with multimodal exercise (n = 10). Single leucine, approximately 2000 steps/day, and whey comparisons provided insufficient evidence of V.O2 preservation. Recovery evidence from three programmes was heterogeneous and very uncertain; only one small HDBR cohort had approximately four-week follow-up. Conclusions: V.O2peak/V.O2max consistently declined after short-term HBR, but a precise decline, duration-response relationship, specific countermeasure prescription, and universal recovery time are not established. Minimising avoidable immobility is a plausible clinical implication, not a directly tested intervention. No external funding.

doi.org/10.3390/healthcare14203459 Open access PubMed 42940503 Mechanisms