Percorrer por autor "Herzog, Walter"
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- Changes in passive and active hamstrings shear modulus are not related after a warmup protocolPublication . Pimenta, Ricardo; Correia, José P.; Vaz, João R.; Veloso, António P.; Herzog, WalterThis study aimed to determine whether changes in hamstrings passive and active shear modulus after a warmup protocol are correlated. Twenty males without a history of hamstring strain injury participated. Muscle shear modulus was assessed using ultrasound-based shear wave elastography at rest and during isometric contractions at 20% of maximal voluntary isometric effort before and immediately after a warmup protocol. Changes in passive shear modulus did not seem to be associated with changes in active shear modulus. The results of this study suggest that changes in passive and active hamstring shear modulus are not associated after a standardized warmup intervention.
- Hamstrings passive and active shear modulus : implications of conventional static stretching and warmupPublication . Pimenta, Ricardo; Correia, José P.; Vaz, João R.; Veloso, António P.; Herzog, WalterPurpose: This study compares the acute effects of a static stretching and a warmup protocol on the active and passive shear modulus of the hamstring muscles. Methods: Muscle shear modulus was assessed at rest and during isometric contractions at 20 % of maximal voluntary isometric contraction (MVIC). Results: After stretching, the passive shear modulus pattern was not altered, while at 20 % MVIC the biceps femoris short head (BFsh) and semimembranosus showed a shear modulus increase and decrease, respectively, which resulted on BFsh-SM pair differences (pre: 3.8 ± 16.8 vs. post: 39.3 ± 25.1 kPa; p < 0.001; d = 1.66) which was accompanied by a decrease of 18.3 % on MVIC. Following the warmup protocol, passive shear modulus remained unchanged, while active shear modulus was decreased for the semitendinosus (pre: 65.3 ± 13.5 vs. post: 60.3 ± 12.3 kPa; p = 0.035; d = 0.4). However, this difference was within the standard error of measurement (10.54 kPa), and did not impact the force production, since it increased only 1.4 % after the warmup. Conclusions: The results of this study suggest that the passive and active shear modulus responses of the individual hamstring muscles to static stretching are muscle-specific and that passive and active hamstring shear modulus are not changed by a standard warmup intervention.