Introduction: It has been shown that joint power at the hip and knee contributes to pedaling power (Elmer et al. 2011), suggesting that muscles around the two joints are the major power source of a pedaling motion. However, detailed knowledge of cycling traininginduced muscular hypertrophy is scarce. Our study (Ema et al. in press) suggested that the training with simultaneous extensions of the knee and hip joints induces muscle-specific hypertrophy of the quadriceps femoris (vasti increase in volume whereas the rectus femoris does not). A similar hypertrophic response associated with the difference in the anatomical features (biarticular or monoarticular nature) has been observed among the triceps brachii as a result of multijoint dumbbell press training (Wakahara et al. 2013). Based on these findings, it was hypothesized that 1) regular training of competitive cycling induces muscle-specific hypertrophy of hip and knee synergistic muscles, and 2) the muscle-specificity in hypertrophic responses is related to the difference in the anatomical features of these muscles. We tested these hypotheses with a longitudinal observation of competitive cyclists. Methods: T1-weighted magnetic resonance images (slice thickness: 1 cm) of the trunk and thigh were obtained from 12 varsity cyclists (10 males, 2 females; experience: 0.1 - 10.7 yr) twice (6 months in-between; cycling training: 15 hours per week on average). From the images, the volumes of each muscle of the quadriceps femoris, hamstring and psoas major were determined. Results and Discussion: A two-way analysis of variance showed a significant time x muscle interaction for the muscle volume (P < 0.001). The regular training of competitive cycling induced significant gains in the volumes of the vastus lateralis (4.0 ± 2.4%), vastus medialis (2.9 ± 1.9%), vastus intermedius (3.2 ± 2.8%), biceps femoris short head (3.1 ± 3.1%), semitendinosus (3.0 ± 3.5%) and psoas major (4.8 ± 2.8%). On the other hand, the volumes of the rectus femoris, biceps femoris long head and semimembranosus remained unchanged. These results support the first and partly the second hypothesis. It is suggested that the muscle-specificity in hypertrophic responses to the competitive cycling training is linked to the differences in the number of joints that the muscles cross, with one exception in the hamstring.
© Copyright 2014 19th Annual Congress of the European College of Sport Science (ECSS), Amsterdam, 2. - 5. July 2014. Published by VU University Amsterdam. All rights reserved.