Recent studies have reported that resistance training increases the cross-sectional areas (CSAs) of tendons; however, this finding has not been consistently observed across different studies. If tendon CSA increases through resistance training, resistance-trained individuals should have larger tendon CSAs as compared with untrained individuals. Therefore, in the current study, we aimed to investigate whether resistance training increases tendon CSAs by comparing resistance-trained and untrained individuals. Sixteen males, who were either body builders or rugby players, were recruited as the training group, and 11 males, who did not participate in regular resistance training, were recruited into the control group. Tendon CSAs and muscle volumes of the triceps brachii, quadriceps femoris, and triceps surae were calculated from images obtained by using magnetic resonance imaging. The volumes of the 3 muscles were significantly higher in the training group than in the control group (P < .001 for all muscles). However, a significant difference in tendon CSAs was found only for the distal portion of the triceps surae tendon (P = .041). These findings indicate that tendon CSA is not associated with muscle volume, suggesting that resistance training does not increase tendon CSA.
Atsuki Fukutani and Toshiyuki Kurihara
Mitsuo Otsuka, Jae Kun Shim, Toshiyuki Kurihara, Shinsuke Yoshioka, Makoto Nokata and Tadao Isaka
In sprinters with different levels of block acceleration, we investigated differences in their three-dimensional force application in terms of the magnitude, direction, and impulse of the ground reaction force (GRF) during the starting block phase and subsequent two steps. Twenty-nine participants were divided into three groups (well-trained, trained, and nontrained sprinters) based on their mean anteroposterior block acceleration and experience with a block start. The participants sprinted 10 m from a block start with maximum effort. Although the mean net resultant GRF magnitude did not differ between the well-trained and trained sprinters, the net sagittal GRF vector of the well-trained sprinters was leaned significantly further forward than that of the trained and nontrained sprinters during the starting block phase. In contrast, during the starting block phase and the subsequent steps, the transverse GRF vectors which cause the anteroposterior and mediolateral acceleration of the whole-body was directed toward the anterior direction more in the well-trained sprinters as compared with the other sprinters. Therefore, a more forward-leaning GRF vector and a greater anteroposterior GRF may particularly allow well-trained sprinters to generate a greater mean anteroposterior block acceleration than trained and nontrained sprinters.