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

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 (Vo2max) 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 Vo2max. 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. Vo2max declined linearly across bed rest duration. No statistical difference in the decline among studies reporting Vo2max as l/min (–0.3% per day) compared with studies reporting Vo2max 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 Vo2max. However, 15–26% of the variation in the decline in Vo2max was explained by the pre-bed-rest Vo2max levels, independent of the duration of bed rest (i.e., higher pre-bed-rest Vo2max levels were associated with larger declines in Vo2max). 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 relevan...
Source: Journal of Applied Physiology - Category: Physiology Authors: Tags: RESEARCH ARTICLE Source Type: research