The purpose of this study was to investigate the influence of tension, contraction time, and joint angle on the cardiovascular responses of isometric exercise.
Twenty-six normotensive male subjects performed isometric contractions of knee extensors at 60%, 80%, 100% maximal voluntary contraction(MVC) for 10 seconds, 80% MVC at three knee joint positions(30°, 45°, 90°) for 10 seconds and 80% MVC for
10
seconds and 20 seconds. Peak torques were measured for each contraction. In addition, blood pressure and heart rate were recorded simultaneously at rest and immediately following each contraction.
The mean isometric peak torques of young age group were significantly higher than those of old age group at all examined joint angles(p<0.05). Blood pressure and heart rate rise were proportional to the percentage of MVC rather than to the
absolute
amount of force produced, but blood pressure and heart rate of the group exercising at 100% of MVC were not significantly higher than those of the group exercising at 80% of MVC(p>0.05).
Blood pressure and heart rate of the group exercising at 20 seconds were significantly higher than those exercising at 10 seconds(p<0.05).
It was concluded that the blood pressure and heart rate changes to isometric exercise were influenced by the percentage of MVC and contraction time, but not by the joint angle.
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