Test of exercise experiments proposed for the MIR '92 mission

During exercise, heart rate and blood pressure drives can be elicited by receptors situated in the interstitial space of the muscle. It was recently shown that these receptors are sensitive to the local state of hydration: Increased reflex responses during dehydration were shown in rat preparates as well as in humans during dynamic and static exercise. Weightlessness could affect these receptor mechanisms through the redistribution of body fluids and through secondary changes in the interstitial structure. To investigate such effects we suggested to determine heart rate and blood pressure responses to light isometric calf exercise at different calf volumes during the MIR '92 mission (experiment ISX). The First North Sea Parabolic Flight campaign provided an opportunity to test the setup and some operational aspects of this experiment. The experience of this campaign led to some modifications of the original setup.