Correlation between Passive and Active Shear Moduli after a Fatigue Task

Objectives: The purpose of this study was to determine whether hamstrings’ passive and active shear moduli measured before and after a fatigue task are correlated. Studying the correlation between passive and active shear moduli is important because, if correlated, passive SWE could provide a quicker assessment without requiring fatigue-inducing voluntary contractions. Methods: Forty-seven football players with no history of hamstring strain injury participated. Muscle shear modulus was assessed only in the dominant lower-limb (dominance defined as the preferred kicking limb) using ultrasound-based shear wave elastography at rest and during isometric contractions at 20% of maximal voluntary isometric effort before and immediately after a 10 × 30 m repeated sprint protocol. Results: Regarding sprint performance, a significant decrease of 8.3% was seen between the first and the last sprints (first: 7.14 ± 0.27 m/s; last: 6.60 ± 0.31 m/s; p < 0.001; dz = 1.88 [1.40–2.35]). In relation to the peak torque normalized to bodyweight, a significant decrease of 9.2% was seen between pre and post (pre: 1.98 ± 0.30 Nm/kg; post: 1.83 ± 0.31 Nm/kg; p < 0.001; dz = 0.89 [0.78–0.95]). Regarding the correlation analysis, none of the passive and active shear moduli measures was significantly correlated in any condition (Bonferroni correction for multiple comparisons, significance threshold set at p < 0.004). Conclusions: The results suggest that the hamstrings’ passive and active shear moduli are not correlated after a fatigue task.