Comparison of two modalities when exerting isometric contractions.

In order to verify whether the method employed to obtain an isometric contraction has any effects on the time for which the contraction can be sustained as well as the consequent cardiocirculatory responses, nine male subjects, from 23 to 42 years of age, carried out isometric contractions of the elbow flexor muscles against either a suspended weight (W) or a fixed strain gauge (SG). The maximum voluntary contraction (MVC) appears to be identical in both instances; and, for a given percentage of MVC, the limit-time of the isometric contraction and its accompanying heart rate changes reveal no significant differences in the two cases.