RESPIRATORY AND CARDIOVASCULAR-RESPONSES TO STATIC HANDGRIP EXERCISE IN HUMANS

We studied the time course of respiratory and cardiovascular responses by evaluating changes in the breathing pattern, mean blood pressure ( MBP), and heart rate elicited by 3 min of static handgrip at 15, 25, a nd 30% of the maximum voluntary contraction (MVC) in 15 healthy volunt eers. Muscle tension and integrated electromyographic activity remaine d fairly constant during each trial. During 15% MVC bouts, initially o nly mean inspiratory flow increased; then, tidal volume and minute ven tilation (VI) also rose progressively. No significant changes in MBP a nd heart rate were observed. During 25 and 30% MVC bouts, not only did mean inspiratory flow, VT, and VI increase but MBP and heart rate inc reased as well. A slight and delayed rise in respiratory rate was also observed. Unlike 15 and 25% MVC handgrip, 30% MVC handgrip caused a s mall decrease in end-tidal Pco(2). Changes in the pattern of breathing occurred more promptly than those in cardiovascular variables in the majority of subjects. Furthermore, we found a positive correlation bet ween changes in QI and those in cardiovascular variables at the end of 25 and 30% MVC trials. This study indicates that respiratory and card iovascular responses to static handgrip exercise are controlled indepe ndently.