Introduction: We examined the relationship between passive stiffness of posterior hip and thigh muscles and muscle power output before and after normalization of passive stiffness to muscle cross-sectional area (CSA).
Methods: Pearson correlation coefficients (r) were used to assess the relationships between the normalized and non-normalized slopes of the initial (phase 1) and final (phase 2) portions of the angle-torque curve and peak power output (Pmax).
Results: A significant positive relationship was observed between the non-normalized slope of phase 1 and Pmax (r = 0.723; P ≤ 0.001); however, no correlations were observed between the normalized slope of phase 1 and Pmax (r = 0.244; P = 0.299) nor between Pmax and the normalized and non-normalized slopes of phase 2 (r = -0.159-0.418; P = 0.067-0.504).
Conclusions: The findings suggest that muscle size, rather than stiffness, accounted for a significant portion of the variance in muscle power output.
Keywords: musculotendinous unit; normalization; passive stiffness; power; vertical jump performance.
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