A decrease in the responsiveness of heart muscle that sometimes occurs after long periods of weightlessness and may be marked by decrease in blood volume and pooling of the blood in the legs upon return to normal conditions.
Classic Signs: Fatigue, weakness, breathlessness, pain.
An overview of the issues: physiological effects of bed rest and restricted physical activity.
Convertino VA, Bloomfield SA, Greenleaf JE.
Physiology Research Branch, Clinical Sciences Division, Brooks Air Force Base, TX 78235, USA.
Medicine and Science in Sports and Exercise 1997 Feb;29(2):187-90.
Reduction of exercise capacity with confinement to bed rest is well recognized. Underlying physiological mechanisms include dramatic reductions in maximal stroke volume, cardiac output, and oxygen uptake. However, bed rest by itself does not appear to contribute to cardiac dysfunction. Increased muscle fatigue is associated with reduced muscle blood flow, red cell volume, capillarization and oxidative enzymes. Loss of muscle mass and bone density may be reflected by reduced muscle strength and higher risk for injury to bones and joints. The resultant deconditioning caused by bed rest can be independent of the primary disease and physically debilitating in patients who attempt to reambulate to normal active living and working. A challenge to clinicians and health care specialists has been the identification of appropriate and effective methods to restore physical capacity of patients during or after restricted physical activity associated with prolonged bed rest. The examination of physiological responses to bed rest deconditioning and exercise training in healthy subjects has provided significant information to develop effective rehabilitation treatments. The successful application of acute exercise to enhance orthostatic stability, daily endurance exercise to maintain aerobic capacity, or specific resistance exercises to maintain musculoskeletal integrity rather than the use of surgical, pharmacological, and other medical treatments for clinical conditions has been enhanced by investigation and understanding of underlying mechanisms that distinguish physical deconditioning from the disease. This symposium presents an overview of cardiovascular and musculoskeletal deconditioning associated with reduced physical work capacity following prolonged bed rest and exercise training regimens that have proven successful in ameliorating or reversing these adverse effects.
Updated on: Apr. 18, 2013