Daniel A. GartenƗ1, Adam Bruengerǂ1, Thomas Lowderǂ1, Michael Gallagherǂ1 1University of Central Arkansas, Conway, Arkansas

Limited research has investigated the effects of stretching of antagonist musculature on agonist muscle activity and functional performance. The results of two previous studies have shown that stretching of the hip flexors prior to countermovement jumps increased average jump height. PURPOSE: The primary purpose of this study was to determine if hip flexor stretching prior to countermovement jumps causes acute changes in antagonist and agonist muscle activity. The second purpose was to evaluate the relationship between muscle activity and the changes in vertical jump height and power. METHODS: Nine physically trained participants (Male; age: 23yr ± 4yr; ht: 69.4in ± 3.6in; wt: 78.2kg ± 12.5kg; body fat%: 8.7% ± 1.9%) performed testing in a single session. Participants performed three vertical jumps on a force platform prior to and after performing three 1-minute stretches of the iliopsoas per leg. Muscle activity of the dominant leg gluteus maximus, biceps femoris, iliopsoas, and erector spinae were recorded via electromyography and normalized to maximal voluntary isometric contraction muscle activity. RESULTS: Results showed no significant change (p > 0.05) in muscle activity of the erector spinae group, gluteus maximus, biceps femoris, or iliopsoas. Significant increases were found in passive hip extension range of motion (t (8) = -2.53, p = 0.03), and significant decreases found in subsequent jump height (t (8) = 2.73, p = 0.02), peak power (t (8) = 2.73, p = 0.02), and mean power (t (8) = 2.72, p = 0.02). CONLUSION: These results contradict previous research and indicate that further research needs to be performed to determine the effects of antagonist stretching prior to power performance. These contradictions in results can potentially be attributed to small sample size, differences in stretch duration compared to previous studies, or timing of pre- and post-testing.

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