HEART-RATE AND BLOOD-PRESSURE RESPONSES TO ISOMETRIC-EXERCISE IN YOUNG AND OLDER MEN

The aim of this study was to examine the isometric endurance response and the heart rate and blood pressure responses to isometric exercise in two muscle groups in ten young (age 23-29 years) and seven older (a ge 54-59 years) physically active men with similar estimated forearm a nd thigh muscle masses. Isometric contractions were held until fatigue using the finger flexor muscles (handgrip) and with the quadriceps mu scle (one-legged knee extension) at 20%, 40%, and 60% of the maximal v oluntary contraction (MVC). Heart rate and arterial pressure were rela ted to the the individual's contraction times. The isometric endurance response was longer with handgrip than with one-legged knee extension , but no significant difference was observed between the age groups. T he isometric endurance response averaged 542 (SEM 57), 153 (SEM 14), a nd 59 (SEM 5) s for the handgrip, and 276 (SEM 35), 94 (SEM 10) and 48 (SEM 5) s for the knee extension at the three MVC levels, respectivel y. Heart rate and blood pressure became higher during one-legged knee extension than during handgrip, and with increasing level of contracti on. The older subjects had a lower heart rate and a higher blood press ure response than their younger counterparts, and the differences were more apparent at a higher force level. The results would indicate tha t increasing age is associated with an altered heart rate and blood pr essure response to isometric exercise although it does not affect isom etric endurance.