Repeatability and sensitivity of passive mechanical stiffness measurements in the triceps surae muscle-tendon complex

Platelet-rich plasma enhances remodeling of combined gastrocnemius muscle and Achilles tendon injuries in rat model: Reducing fibrosis, modulating gene (MMP9, Bax, HMGB1, and IGF) expression, and restoring histopathological and ultrastructural changes

Muscle and tendon injuries are prevalent occurrences during sports activities. Platelet-rich plasma (PRP) is known for its rich content of factors essential for wound healing, inflammation reduction, and tissue repair. Despite its recognized benefits, limited information is available regarding PRP's effectiveness in addressing combined surgical injuries to the gastrocnemius muscle and Achilles tendon. The effects of PRP on muscle and tendon injury in rats were assessed through a set of biochemical markers, histopathological examinations, and immunohistochemistry analyses of muscular myogenin, desmin, and tendinous type I collagen. Additionally, mRNA expression levels of Matrix metalloproteinase-9 (MMP-9), Pro-apoptotic Bcl-2 Associated-X-protein (BAX), Insulin-like growth factor (IGF), and High mobility group box 1 protein (HMGB1) genes were evaluated. Induction of muscle and tendon injuries was associated with elevated levels of serum biomarkers such as C-reactive protein (CRP), Aspartate aminotransferase (AST), Lactate dehydrogenase A (LDH), and Creatine Kinase MB (CK-MB), delayed collagen fiber remodeling, and structural abnormalities in myofibrils. Furthermore, there was overexpression of MMP9, Bax, and HMGB1 genes, along with decreased expression of the IGF gene in this group. Treatment with PRP resulted in significant improvement of these reported findings, including enhanced collagen fiber remodeling, elevated levels of desmin and myogenin in muscle tissues, and increased expression of collagen type I in tendons. Additionally, PRP treatment led to reduced expression levels of MMP9, Bax, and HMGB1 genes, while the expression of the IGF gene increased. Overall, PRP treatment demonstrated substantial enhancement of the healing process in both muscle and tendon tissues in a surgical model of gastrocnemius skeletal muscle and Achilles tendon-induced injury. These findings suggest that PRP therapy may offer advantages in the treatment of physical-related injuries.

The effects of eccentric exercise on passive hamstring muscle stiffness: Comparison of shear-wave elastography and passive knee torque outcomes

The aim of our study was to assess eccentric-exercise-induced changes in passive knee joint torque, passive knee joint stiffness and shear modulus at of the hamstring muscles. We hypothesized that eccentric exercise would elicit an increase in all outcomes. Fourteen healthy volunteers (age = 25.5±4.7 years) performed eccentric exercise protocol. Before and after 0h, 1h, 24h and 48h, we measured the shear modulus of hamstring muscles using shear-wave elastography and passive knee joint stiffness on isokinetic dynamometer. After eccentric exercise, the shear modulus of biceps femoris increased after 0h (22.4 ± 34.1 %; p = 0.021) and for semitendinosus after 0h (14.5 ± 4.9 %), 1h (16.2 ± 6.5 %) and 24h (16.6 ± 8.3 %) (p = 0.005-0.015). There were no changes for semimembranosus and no changes in passive knee joint moment measures. There were also no correlations between the two methods. Eccentric exercise increased shear modulus of hamstring muscles, while passive joint torque was not affected. This suggests that shear-wave elastography could be more sensitive than torque measures to intra-muscular changes induced by eccentric exercise.