Objective: The present study was designed to test the effects of the reversal of antagonists on the peak rate of tension development (dF/dtmax) of the 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 protocols, except that the control group performed maximal isometric contractions of the elbow extensors and the experimental group executed a maximal isometric elbow flexion contraction immediately before a maximal elbow extension contraction. Both groups performed 5 cycles of a 2-second contraction with 22-second rest periods between agonist muscle contractions and were evaluated at 4 test sessions spaced 2 weeks apart. Main Outcome Measures: All measurements were done with the shoulder and elbow at 90° of flexion in the sagittal plane to ensure reproducibility. A load cell was used to measure elbow extension moment and to calculate the peak rate of tension development (dF/dtmax). Biceps and triceps brachii surface electromyographic activity was monitored concurrently. The electromyographic measures were mean spike (peak-to-peak) amplitude and mean spike frequency of the biceps and triceps brachii activity. Results: Intraclass dF/dtmax and electromyographic reliability was good (r ≥ .72) in both groups. Because biceps electromyographic measures were considerably less reliable (r ≤ .53), they were not included in our analysis. While dF/dtmax increased quadratically in both groups (p < .05), the experimental group was on average 36.1Nm · s-1 (63%) greater across sessions 2 to 4 (p < .05). In contrast, triceps electromyographic activity did not differ significantly between groups (p > .05). The means averaged across groups exhibited a quadratic increase from session 1 to session 4: 91μV or 48% for mean spike amplitude (p < .05) and 7Hz or 16% for mean spike frequency (p < .05). Conclusions: The greater dF/dtmax for the experimental group was not associated with increased electromyographic activity. The experimental group appeared to use the biomechanic properties of the pretensioned extensor muscle-tendon complex, rather than neurologic biasing, to accomplish its power gains.
- Isometric contraction
ASJC Scopus subject areas
- Physical Therapy, Sports Therapy and Rehabilitation