Author(s): SCHWIETE, C., BROICH, H., MESTER, J., BEHRINGER, M., Institution: GOETHE UNIVERSITY, Country: GERMANY, Abstract-ID: 473

INTRODUCTION:
Shear-wave elastography is an increasingly used method to evaluate muscle stiffness after exercise-induced muscle damage [1]. Research indicates that shear-wave speed variations are not uniform across a muscle group, with notable differences between [2] and even within muscle heads [3]. This study aimed to explore the uniformity of muscle stiffness changes across and within muscle heads following maximal eccentric exercise.

METHODS:
Fourteen trained male participants (26.6 ± 3.1 years, 81.8 ± 8.2 kg, 180.5 ± 7.3 cm) underwent muscle stiffness evaluation at six distinct sites within the hamstring muscle utilizing shear-wave elastography. Subjects performed 5 x 15 maximal eccentric leg curls at 210°/s on an isokinetic dynamometer and muscle stiffness was assessed before, immediately after training, and on the consecutive four days (24 h – 96 h post).

RESULTS:
There was no time-by-point interaction for shear-wave elastography (F25, 360 = 0.60, p = 0.93). The main effects of time (F4.01, 288.9 = 2.98, p = 0.02) revealed a significant increase in muscle stiffness from pre (2.04 ± 0.15 m/s) to post (2.11 ± 0.14 m/s) and 24 h post (2.11 ± 0.14 m/s). A significant main effect was also observed for the specific points of measurement (F5, 72 = 4.85, p = 0.0007).

CONCLUSION:
Maximal eccentric exercise induced an immediate and sustained increase in hamstring muscle stiffness, observable up to 24 hours post-exercise. The findings suggest spatial heterogeneity in stiffness changes across the different hamstring measurement locations, possibly due to non-uniform muscle damage [4] or fiber activation [5].

References:
[1] Licen, U; Kozinc, Z. (2022). Using Shear-Wave Elastography to Assess Exercise-Induced Muscle Damage: A Review. Sensors, 22, 7574. https://doi.org/10.3390/s22197574
[2] Kawama, R; Yanase, K; Hojo, T; Wakahara, T. (2022). Acute changes in passive stiffness of the individual hamstring muscles induced by resistance exercise: effects of contraction mode and range of motion. European Journal of Applied Physiology, 122: 2071-2083. https://doi.org/10.1007/s00421-022-04976-6
[3] Kisilewicz A, Madeleine P, Ignasiak Z, Ciszek B, Kawczynski A, Larsen R. (2020) Eccentric Exercise Reduces Upper Trapezius Muscle Stiffness Assessed by Shear Wave Elastography and Myotonometry. Frontiers in Bioengineering and Biotechnology 8: 928. https://doi.org/10.3389/fbioe.2020.00928
[4] Green, M; Sinkus, R; Gandevia, S; Herbert, R; Bilston, L. (2012). Measuring changes in muscle stiffness after eccentric exercise using elastography. NMR Biomed, 25, 852-858. doi: 10.1002/nbm.1801
[5] Kinugasa, R; Kawakami, Y; Fukanaga, T. (2006). Quantiative assessment of skeletal muscle activation using functional MRI. Magn. Reson. Imaging, 24, 639-644. doi: 10.1016/j.mri.2006.01.002