Evaluating changes in lower leg muscle hardness after running assessed by ultrasound strain elastography

Abstract

Running injuries often occur due to muscle overuse among runners. Repetitive mechanical loading of the foot and lower leg contributes to an increased load, which results in muscle damage and changes in muscle tis sue and hardness. However, the extent of changes in muscle hardness during running remains unclear. Therefore,this study aimed to assess and compare the muscle hardness of the lower leg muscle using strain elastography be fore and after a running task. Thirteen healthy men were included as study participants. After assessing their foot alignment, we measured the lower leg muscle hardness using an ultrasound imaging system with strain elastogra phy at three time points: pre, post, and 24h after (24-h) the 30-minutes running task. We then examined the changes in muscle hardness and the relationship between the changes in muscle hardness and foot alignment. As a result, the muscle hardness of the tibialis anterior muscle significantly increased between post and 24-h assess ments. Moreover, the increase in muscle hardness of the medial head of the gastrocnemius and flexor digitorum longus muscles between the pre and 24-h assessments were positively correlated with navicular drop and height,respectively. Therefore, these findings suggest the need to approach the ankle plantar flexors when addressing running injuries.