Investigation of the Effect of Joint Angle on Muscle Hardness in Static Stretching of the Gastrocnemius

Static stretching is one of the most popular ways to decrease muscle tone. Muscle tone is evaluated by muscle hardness. To evaluate how muscle tone decreases during static stretching, we have proposed a method that involves using a wearable muscle hardness meter. In a previous study on the rectus femoris, we sometimes observed a muscle hardness increase during self-static stretching. We did not consider the degree of elongation of the muscle; however, this does actually affect muscle hardness. In this paper, we investigate the effect of joint angle on muscle hardness in self-static stretching of the gastrocnemius. We measured the muscle hardness of the medial head and the lateral head of the gastrocnemius and the dorsiflexion angle of the ankle joint during static stretching. In some cases, when the joint angle increased during static stretching, muscle hardness tended to increase. This result suggests that we should consider muscle elongation when evaluating muscle hardness during static stretching.