Antigravity Effects of Leg Exercise

Abstract

Rosenhamer, G. Antigravity effects of leg exercise. Acta physiol. scand. 1968. 72. 72–80, To investigate the effects of leg exercise on the overall tolerance to exaggerated gravitational stress, 8 subjects were exposed for 13 min to a threefold increase of the force of gravity in centrifuge experiments (+ 3 Gz) while in the sitting position, both during motionless resting and when exercising at 600 kpm/min on a bicycle ergometer. In all subjects, continuous leg exercise prevented the occurrence of circulatory collapse. which otherwise became imminent in 5 subjects after 5 to 12 min in the resting condition as evidenced by blackout or rapid increase in heart rate. Subjectively, exercise was experienced as less stressful than the resting condition. The improved circulatory stability with exercise was also reflected by uniformity of individual heart rate responses, the group mean value increasing from 152 to 160 beats/min during the 6th to 12th min.

Acceleration Stress and Effects of Propranolol on Cardiovascular Responses

“…The finding that propranolol did not reduce subjective G tolerance is consistent with the observations of Cohen and Brown (1969) who, however, used a considerably smaller dose (5 mg) in their experiments. That visual symptoms did not occur when exposure to ACCELERATION STRESS AND PROPRANOLOL 49 7 3 G was combined with leg exercise is in agreement with earlier observations by Rosenhamer (1967), and is a reflection of he exercise-induced increase in arterial mean pressure that has previously been reported to occur at the 3 G level (Linnarsson and Rosenhamer 1968).…”

“…Cardiac output was determined by the indicator dilution technique using indocyanine green (Cardio-Green@) and a Waters X-100 dichromatic densitometer modified electrically to minimize drift and other disturbances in the centrifuge environment. T o produce dye-dilution curves with the subject in the spinning centrifuge, dye injections as well as the subsequent withdrawal and reinfusion of arterial blood through the densitometer cuvette were made by a remote-controlled injection system described elsewhere (Rosenhamer 1967(Rosenhamer , 1968. T h e amount of dye injected for each determination was 1.00 ml of a 0.5 % aqueous solution of indocyanine dye, and the rate of withdrawal of blood through the cuvette was 20 ml/min.…”