Effects of moderate physical exercise during four weeks of bed rest on circulatory functions in man.

Various effects on circulatory functions of light to moderate physical exercise during 4 weeks of bed rest were studied in 6 subjects. During exercise narrow cuffs inflated to 60 ram. Hg were worn on the upper thighs. Changes in plasma volume during and after bed rest paralleled those characteristic of simple bed rest. In contrast to simple bed rest, the major loss of red cell mass was noted at the end of bed rest and not during ambulation following bed rest. The mean resting heart rate for all subjects increased 15 beats per minute during bed rest. The degree of postural intolerance after bed rest appeared as marked as that observed after absolute bed rest. Physical endurance on the treadmill was decreased after bed rest.