HOW ARE TONIC AND PHASIC CARDIOVASCULAR CHANGES RELATED TO CENTRAL MOTOR COMMAND

We examined the influence of central motor command on heart rate, resp iration, and peripheral vascular activity. Central command was enhance d or reduced using tendon vibration. Muscle tension was held constant permitting the examination of variation in central command. Experiment 1 demonstrated in 13 college-aged males an enhancement of heart rate and vascular responses to an isometric, extensor contraction when vibr ation of the flexor tendon was added. Experiment 2 asked whether chang es in central command interacted with phasic cardiovascular changes su ch as stimulus-linked anticipatory cardiac deceleration. Twenty colleg e-aged males performed either an isometric flexor or extensor contract ion with or without flexor tendon vibration. As expected, vibration en hanced cardiovascular change with extensor contraction more than with flexor contraction. Relative to control contractions, however, the fle xor change was not an absolute decrease in cardiovascular change. More importantly, tendon vibration failed to alter phasic cardiovascular c hanges. Force and central commands for force induce cardiovascular cha nge, but this change seems independent of phasic changes induced by th e anticipation and processing of environmental stimuli.