EFFECTS OF ISOKINETIC, ISOTONIC AND ISOMETRIC SUBMAXIMAL EXERCISE ON HEART-RATE AND BLOOD-PRESSURE

The purpose of the present study was to compare arterial pressure (AP) and heart rate (HR) responses to submaximal isokinetic, isotonic and isometric exercises currently employed in physical rehabilitation ther apy in terms of both magnitude and time-course. To this aim AP and HR were continuously and noninvasively measured in ten healthy subjects p erforming isokinetic, isotonic and isometric exercises at the same rel ative intensity. Isokinetic and isotonic exercises consisted of 30 kne e extension/flexion repetitions at 40% of maximal effort. Isokinetic s peed was set at 180 degrees . s(-1). Isometric exercise consisted of a 60-s knee extension at 40% maximal voluntary contraction. The AP show ed a rapid and marked increase from the onset of all types of exercise progressing throughout the exercises. Peak systolic (SAP) and diastol ic (DAP) arterial pressure were 190.7 (SEM 8.9) and 121.6 (SEM 7.8) mm Hg during isokinetic and 197.6 (SEM 11.2) and 128.3 (SEM 7.7) mmHg dur ing isotonic exercise, respectively. During isometric exercise peak SA P and DAP were 168.1 (SEM 6.3) and 102.1 (SEM 3.7) mmHg, respectively [both lower compared to isokinetic and isotonic exercise (P < 0.05)]. The HR rose abruptly and after five isokinetic and isotonic repetition s it had already increased by about 30 beats . min(-1), continuing to rise throughout the exercises. The HR response to isometric exercise w as significantly less (P < 0.05) at all times. An immediate fall in AP , undershooting resting levels; was observed at the cessation of all t ypes of exercise, being more marked after isokinetic and isotonic exer cise. These results indicate that submaximal exercise of a dynamic typ e induces greater AP responses than intensity-matched isometric exerci se and that even submaximal endurance-type rehabilitation exercise yie lds an elevated functional stress on the cardiovascular system which c ould precipitate hazardous events particularly in subjects with unreco gnized cardiac diseases.