Effects of strict prolonged bed rest on cardiorespiratory fitness: Systematic review and meta-analysis

Mathias Ried-Larsen, Hugo M. Aarts, Michael Joseph Joyner

Research output: Contribution to journalReview article

5 Scopus citations

Abstract

The aim of this systematic review and meta-analysis [International Prospective Register of Systematic Reviews (PROSPERO) CRD42017055619] was to assess the effects of strict prolonged bed rest (without countermeasures) on maximal oxygen uptake (V.O2max) and to explore sources of variation therein. Since 1949, 80 studies with a total of 949 participants (±90% men) have been published with data on strict bed rest and V.O2max. The studies were conducted mainly in young participants [median age (interquartile range) 24.5 (22.4-34.0) yr]. The duration of bed rest ranged from 1 to 90 days. V.O2max declined linearly across bed rest duration. No statistical difference in the decline among studies reporting V.O2max as l/min (<0.3% per day) compared with studies reporting V.O2max normalized to body weight (ml•kg<1•min<1; <0.43% per day) was observed. Although both total body weight and lean body mass declined in response to bed rest, we did not see any associations with the decline in V.O2max. However, 15-26% of the variation in the decline in V.O2max was explained by the pre-bed-rest V.O2max levels, independent of the duration of bed rest (i.e., higher pre-bed-rest V.O2max levels were associated with larger declines in V.O2max). Furthermore, the systematic review revealed a gap in the knowledge about the cardiovascular response to extreme physical inactivity, particularly in older subjects and women of any age group. In addition to its relevance to spaceflight, this lack of data has significant translational implications because younger women sometimes undergo prolonged periods of bed rest associated with the complications of pregnancy and the incidence of hospitalization including prolonged periods of bed rest increases with age. NEW &NOTEWORTHY Large interindividual responses of maximal oxygen uptake (V.O2max) to aerobic exercise training exist. However, less is known about the variability in the response of V.O2max to prolonged bed rest. This systematic review and metaanalysis showed that pre-bed-rest V.O2max values were inversely associated with the change in V.O2max independent of the duration of bed rest. Moreover, we identified a large knowledge gap about the causes of decline in V.O2max, particularly in postmenopausal women, which may have clinical implications.

Original languageEnglish (US)
Pages (from-to)790-799
Number of pages10
JournalJournal of Applied Physiology
Volume123
Issue number4
DOIs
StatePublished - Oct 1 2017

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Keywords

  • Bed rest
  • Cardiorespiratory fitness
  • Exercise test
  • Microgravity
  • Spaceflight

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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