Early detection of exercise-induced muscle damage using elastography

Purpose This study aimed to determine whether an increase in muscle shear modulus measured 30 min after eccentric exercise (30 min) reflects the magnitude of force deficit measured 48-h post-exercise (48 H). Methods A total of 53 healthy participants were distributed in five groups. Four groups performed either repeated eccentric elbow flexions or knee extensions at either a low or high load. A fifth group performed repeated concentric elbow flexions (control load). Results A significant decreased peak torque was found for elbow flexors and knee extensors 48 h after the eccentric exercises (all P values < 0.001). A significant increase in shear modulus was found at 30 min for the elbow flexors for low (+70.5 +/- 44.3%, P < 0.001) and high load (+153.9 +/- 192.4%, P < 0.001). Similarly, the shear modulus of knee extensors increased for low (+26.7 +/- 19.1%, P < 0.001) and high load (+79.4 +/- 67.1%, P < 0.001). The relative increase in shear modulus measured at 30 min was significantly correlated to the relative decrease in peak torque measured at 48 H for both elbow flexors (r = -0.80) and knee extensors (r = -0.82). A further analysis suggested that biceps brachii and rectus femoris were more affected by muscle damage than their synergists. Conclusion This study shows that an increase in muscle shear modulus measured 30 min after a damaging exercise reflects the decrease in peak torque measured at 48 H. Shear modulus may therefore, provide a useful tool for coaches and clinicians to non-invasively estimate the amount of muscle damage induced by a damaging exercise.