Changes in the hardness of the gastrocnemius muscle during a Kendo training camp as determined using ultrasound real-time tissue elastography

Abstract

Kendo is a high load-type sport, especially for the lower leg muscles. The purpose of this study was to evaluate changes in the hardness of the gastrocnemius medialis (GM) using real-time tissue elastography (RTE) during training at a Kendo training camp. Eleven college male Kendo athletes participated in a 5-day Kendo training camp, and the hardness of the GM, the circumference of the lower legs, and the ankle range of motion (ROM) were examined dur- ing the course of training. The strain ratio of the GM to a reference material was used to esti- mate changes in muscle hardness during the training period. The results showed that the strain ratio of the GM significantly increased at days 3, 4, and 5, in comparison to the baseline values obtained prior to training (p < 0.05), indicating that the hardness of the GM increased after high-intensity exercise. Meanwhile, the circumference of the lower leg did not change over the course of training; while the ROM values significantly decreased at days 4 and 5 relative to the baseline, suggesting the increased muscle hardness resulted from increased muscle stiff- ness. These results suggest the muscle hardness of athletes who engage in repetitious high load- type sports are tense on the next day of hard training, and the hardness continues, as in this case, until the last day of camp. In addition, RTE measurements of muscle hardness may allow a more sensitive detection of changes in muscle properties than what is possible with ROM measurements.