Cardiovascular Responses to Isotonic and Isometric Exercise in Young Subjects

Muscular exercise has long been known to play a vital role in health and maintenance of body fitness.To assess and compare cardiovascular responses to isotonic and isometric exercise in young healthy subjects.Ten apparently healthy male subjects aged16 to 26 years, who were not accustomed to physical exercise, performed different levels of isotonic and isometric exercise. Heart rate (HR), systolic blood pressure (SBP) and diastolic blood pressure (DBP) were determined before and after the exercise. Isotonic (dynamic) exercise was achieved on bicycle ergometer, based on the modified Leeds University method while the two (sub-maximal and maximal) levels of isometric exercise were achieved by lifting loads of varied weights in static position.In maximal isotonic exercise, it was observed that the HR was significantly increased by 67.3 ± 9.0% (p < 0.001). In sub-maximal and maximal levels of isometric exercise, the HR was elevated by 12.3 ± 2.7% (p < 0.05) and 24.4 ± 5.0% (p < 0.001), respectively. In maximal isotonic exercise, the SBP was also increased significantly by 21.8 ± 3.9% (p < 0.01) whereas in sub-maximal isometric exercise, it was slightly elevated by 5.0 ± 1.8% (p > 0.5) but significantly increased in maximal isometric exercise, by 24.4 ± 5.0% (p < 0.001). However, in maximal isotonic exercise, DBP was slightly elevated by 12.4 ± 5.0% (p > 0.5) but significantly increased in sub-maximal and maximal isometric exercise by 20.4 ± 4.0% (p < 0.01) and 30.9 ± 5.0% (p <0.001), respectively. Inisotonic exercise, changes in HR and SBP were found to be greater than that of isometric exercise but changes in DBP was observed to be higher in isometric exercise.

Key Words: Cardiovascular, isotonic, isometric, exercise