The reversal of antagonists facilitates the peak rate of tension development

Objective: The present study was designed to test the effects of the revers al of antagonists on the peak rate of tension development (dF/df(max)) of t he elbow extensors. Design: Experimental, with matched controls. Setting: A biomechanics research laboratory. Participants: Twenty-six healthy women without a history of upper extremity injury or neurologic disorder, randomly assigned to experimental (n = 13) or control (n = 13) groups. Interventions: Two groups of healthy subjects followed identical exercise p rotocols, except that the control group performed maximal isometric contrac tions of the elbow extensors and the experimental group executed a maximal isometric elbow flexion contraction immediately before a maximal elbow exte nsion contraction. Both groups performed 5 cycles of a 2-second contraction with 22-second rest periods between agonist muscle contractions and were e valuated at 4 test sessions spaced 2 weeks apart. Main Outcome Measures: All measurements were done with the shoulder and elb ow at 90 degrees of flexion in the sagittal plane to ensure reproducibility . A load cell was used to measure elbow extension moment and to calculate t he peak rate of tension development (dF/df(max)). Biceps and triceps brachi i surface electromyographic activity was monitored concurrently. The electr omyographic measures were mean spike (peak-to-peak) amplitude and mean spik e frequency of the biceps and triceps brachii activity. Results: Intraclass dF/dt(max) and electromyographic reliability was good ( r greater than or equal to .72) in both groups. Because biceps electromyogr aphic measures were considerably less reliable (r less than or equal to .53 ), they were not included in our analysis. While dF/dt(max), increased quad ratically in both groups (p < .05), the experimental group was on average 3 6.1Nm.s(-1) (63%) greater across sessions 2 to 4 (p < .05). In contrast, tr iceps electromyographic activity did not differ significantly between group s (p > .05). The means averaged across groups exhibited a quadratic increas e from session 1 to session 4:91 muV or 48% for mean spike amplitude (p (.0 5) and 7Hz or 16% for mean spike frequency (p (.05). Conclusions: The greater dF/dt(max) for the experimental group was not asso ciated with increased electromyographic activity. The experimental group ap peared to use the biomechanic properties of the pretensioned extensor muscl e-tendon complex, rather than neurologic biasing, to accomplish its power g ains.