Effect of clinical bed rest for seven days on physical performance.

Twenty-two healthy men were confined to bed in a hospital ward (clinical bed rest) for one week. Variables related to physical fitness were measured before and immediately after the bed rest period, as well as one and three months thereafter. As a result of bed rest, maximal oxygen uptake, W170 and total Hb decreased to 94%, and calculated blood volume to 93% of the initial value. Hb concentration and Hct were unaltered. Thus, red cell and plasma volumes were proportionately reduced. No significant orthostatic dysfunction developed. The blood lactate peak at maximum work remained unchanged (14.0 mM/l). The resting exertion of noradrenaline decreased moderately during the bed rest period, whilst that of adrenaline was unchanged. Body weight decreased by a mean of 0.7 kg.