Engineering topics
Publications and source records attributed to Popp, Richard L..
Cardiovascular deconditioning from prolonged bed rest not counteracted by mild exercise and requires at least 3 weeks for recovery, report contends. Involves more than simple decrease in volume of plasma; neurohumoral mechanisms, loss of mass of skeletal muscles, and general decrease of body's metabolic needs seem to be major contributors.
The effects of three 2-week periods of bed rest (with and without isometric/aerobic exercise, and separated by 3-week ambulatory recovery periods) on hemodynamic responses to stepwise application of LBNP (-20 to -40 mm Hg) are investigated experimentally in seven physically active male subjects aged 19-21 years. The data are presented in extensive tables and graphs and characterized in detail. It is found that bed rest produces significant changes in the responses of heart rate and end-diastolic volume index which (1) are greater than can be accounted for by lowered plasma volume, (2) persist during the recovery periods, and (3) do not respond to the exercises employed to prevent deconditioning.