Muscle Damage Indicated by Maximal Voluntary Contraction Strength Changes From Immediately to 1 Day After Eccentric Exercise of the Knee Extensors

Instrument-assisted soft tissue mobilization in healthy adults acutely changes the tissue stiffness

This study clarified whether instrument-assisted soft tissue mobilization (IASTM) on the plantar surface changes abductor hallucis and plantar fascia stiffness at rest and medial longitudinal arch height under low- and high-loading conditions. IASTM was performed to one foot of the twenty-eight young men (IASTM condition), and the other foot of them was assigned to the control condition. Using ultrasonography, the resting shear wave propagation velocity of the abductor hallucis and plantar fascia and navicular height in a seated posture were determined. The foot contact area during quiet standing was measured using a foot-scan system. The shear wave propagation velocity of the plantar fascia significantly decreased by 10.8% in the IASTM condition but did not change significantly in the control condition. The magnitude of change in the shear wave propagation velocity of the plantar fascia was negatively correlated (r=- 0.660) with the shear wave propagation velocity of the plantar fascia before IASTM. The interaction of time and condition was not significant for the shear wave propagation velocity of the abductor hallucis, navicular height, or foot contact area. The current study revealed that IASTM on the plantar surface affected tissue stiffness but did not change the structure of the foot.

Mild to moderate damage in knee extensor muscles accumulates after two bouts of maximal eccentric contractions

PURPOSE

This study aimed to determine whether mild to moderate muscle damage accumulates on the knee extensors after two bouts of maximal eccentric contractions performed over two consecutive days.

METHODS

Thirty participants performed an initial bout of maximal eccentric contractions of knee extensors during the first day of the protocol (ECC1). Then, they were separated in two groups. The Experimental (EXP) group repeated the eccentric bout 24 h later (ECC2) while the Control (CON) group did not. Indirect markers of muscle damage (i.e., strength loss, muscle soreness, and shear modulus) were measured to quantify the amount of muscle damage and its time course.

RESULTS

Two days after the initial eccentric session, participants from EXP had a higher strength deficit (- 14.5 ± 10.6%) than CON (- 6.6 ± 8.7%) (P = 0.017, d = 0.9). Although both groups exhibited an increase in knee extensors shear modulus after ECC1, we found a significant increase in muscle shear modulus (+ 13.3 ± 22.7%; P < 0.01; d = 0.5) after ECC2 for the EXP group, despite the presence of mild to moderate muscle damage (i.e., strength deficit about 16%).

CONCLUSION

Although the markers of muscle damage used in the current study were indirect, they suggest that the repetition of two bouts of maximal eccentric contractions with 24 h apart induces additional muscle damage in the knee extensors in presence of mild to moderate muscle damage.

Using Shear-Wave Elastography to Assess Exercise-Induced Muscle Damage: A Review

Shear-wave elastography is a method that is increasingly used to assess muscle stiffness in clinical practice and human health research. Recently, shear-wave elastography has been suggested and used to assess exercise-induced muscle damage. This review aimed to summarize the current knowledge of the utility of shear-wave elastography for assessment of muscle damage. In general, the literature supports the shear-wave elastography as a promising method for assessment of muscle damage. Increases in shear modulus are reported immediately and up to several days after eccentric exercise, while studies using shear-wave elastography during and after endurance events are showing mixed results. Moreover, it seems that shear modulus increases are related to the decline in voluntary strength loss. We recommend that shear modulus is measured at multiple muscles within a muscle group and preferably at longer muscle lengths. While further studies are needed to confirm this, the disruption of calcium homeostasis seems to be the primary candidate for the underlying mechanism explaining the increases in shear modulus observed after eccentric exercise. It remains to be investigated how well the changes in shear modulus correlate with directly assessed amount of muscle damage (biopsy).