Cardiovascular Responses to Isometric Handgrip Exercise

ABSTRACT

Isometric contractions of muscles in upper extremities occur frequently during ordinary daily activities. The isometric handgrip exercise can be one of the best methods for the evaluation and treatment of patients with disability of upper extremity. However these isometric contractions can impose sudden and significant high stresses to the cardiovascular system. The purpose of this study was to document the torque patterns and cardiovascular responses of subjects by the isometric handgrip exercises and hopefully to provide a guidance for the safe evaluations and prescriptions of isometric exercises. Eighty healthy male subjects from 21 to 60 years of age performed isometric handgrip exercises using a Baltimore therapeutic equipment work simulator. The peak torque, time to peak torque, and torque at each second were measured by a six-second isometric strength trial program. The blood pressure and heart rate were measured simultaneously at rest and at each minute during isometric exercises at 30%, 50%, and 70% of the peak torque. There were no differences in the peak torque, time to peak torque, and torque at each second between age groups(p>0.05). After the onset of peak torque, the torque gradually decreased and recorded 72.8% of the peak torque at 6 seconds. The mean arterial pressure and heart rate increased significantly during exercise(p<0.001), but returned to the resting state immediately when the exercise stopped. The mean arterial pressures were significantly different when the duration of exercise prolonged at 50% and 70% of the peak torque(p<0.05). And also the mean arterial pressures increased significantly when the strength of exercise increased as well(p<0.001). We have concluded that attentions should be given to patient's cardiovascular state, and duration and strengh of exercise when the isometric handgrip exercises are prescribed for the evaluation and treatment of patients.