This study examined the influence of regular training in competitive cycling on individual muscle volume of the thigh and psoas major cross-sectionally and longitudinally. T1-weighted magnetic resonance (MR) images of the trunk and right thigh were obtained from eight experienced varsity male cyclists (experience: > 4 years) and 10 untrained men (experiment 1), and from 12 (10 males, two females) varsity cyclists before and after competitive cycling training for 6 months (experiment 2). From the MR images, the volumes of each of the quadriceps femoris and hamstrings, total adductors, gracilis, sartorius, and psoas major were determined. The volumes of the monoarticular thigh muscles, semitendinosus, and psoas major muscles were significantly greater in the experienced cyclists than in the untrained men (experiment 1), and increased significantly after the competitive training for 6 months (experiment 2). In contrast, the volumes of the other biarticular thigh muscles were similar among the experienced cyclists and untrained men (experiment 1), and did not change by competitive cycling training (experiment 2). The results indicate that competitive cycling training induces muscle-specific hypertrophy of the synergistic muscles, especially between the monoarticular and biarticular muscles, leading to quantitative profiles of the musculature in experienced cyclists.
Purpose: This study aimed to investigate the level of muscle activity during sprint running using T2-weighted magnetic resonance imaging. Methods: Fourteen male sprinters (age 21.2 [4.0] y; height 171.8 [4.2] cm, weight 65.5 [5.3] kg, 100-m personal record 11.01 [0.41] s; mean [SD]) performed 3 sets of three 60-m round-trip sprints. Before and after the round-trip sprints, 3 T magnetic resonance imaging scans were performed to obtain the T2 values of the 14 athletes’ lower-extremity muscles. Results: After the 60-m round-trip sprints, the T2 value of the gluteus maximus, long head of biceps femoris, semitendinosus, semimembranosus, adductor brevis, adductor longus, adductor magnus, and gracilis increased significantly. The rate of change in the T2 values before and after the 60-m round-trip sprints was notably higher in the semitendinosus and gluteus maximus than in the other muscles. Conclusions: These findings demonstrate the specific physiological metabolism of the lower-extremity muscles during fast sprinting. There are particularly high levels of muscle activity in the gluteus maximus and semitendinosus during sprint performance.
This study was designed to clarify the relationships between the muscle cross-sectional area of the trunk and thigh and 400-m hurdle time in 12 young adult male athletes include a bronze medalist in the world championships (height 175.4 ± 6.0 cm, body mass 67.9 ± 5.8 kg, 400-m hurdle time 47.89-55.41 s). Crosssectional images from the origin to insertion of the trunk and thigh muscles were obtained using magnetic resonance imaging (MRI). These images were used to calculate the absolute cross-sectional areas of each muscle as indices of muscularity. Stepwise multiple regression analysis was performed to examine the association between the indices and 400-m hurdle time. This analysis produced an equation (adjusted R2 = .868) with the semitendinosus (β = −0.611, P = .001), quadratus lumborum (β = −0.300, P = .044) and adductor brevis (β = −0.395, P = .014) as the explanatory variables. It was concluded that individual differences in 400-m hurdle performance can be explained by the semitendinosus, quadratus lumborum and adductor brevis.
谷中 拓哉 1) 中里 浩介 1)2) 藤田 善也 3)4) 石毛 勇介 1) クロスカントリースキー競技における平昌オリンピックのコース プロフィール取得とプレ大会の公式記録からみるレースの展望: 男子 15km+15km スキーアスロン種目を対象として 1) 国立スポーツ科学センター 〒 115-0056 東京都北区西が丘 3-15-1 2) 青森県スポーツ科学センター 〒 039-3505 青森県青森市大字宮田宇高瀬 22-2 3) 早稲田大学スポーツ科学学術院 〒 359-1192 埼玉県所沢市三ヶ島 2-579-15 4) 公益財団法人全日本スキー連盟 〒 150-0041 東京都渋谷区神南 1-1-1 連絡先 谷中拓哉
Mechanical factors determining the rolling speed in baseball batting. Japan J. Phys. Educ. Hlth. Sport Sci. 62: 33 48, June, 2017 AbstractA wide range of topspin rotation of a bat around the long-axis, referred to as``rolling'', has been observed in baseball batting, but the mechanical reasons for the large variability among individual batters has not been examined. The purpose of this study was to investigate the factors determining this variability in rolling velocity among professional baseball players. Twenty-nine professional batters each performed 8``free-batting'' trials. An electromagnetic tracking device was used to measure the 3-dimensional rotational motion of the bat in each trial. The rolling velocity was 678±376°/s, comprised a negative contribution attributable to the batter's eŠort of exerting torque (Mechanism 1: -1144± 488°/s) and a positive contribution attributable to the gyroscopic eŠect (Mechanism 2: 1808±339°/s). A signiˆcant positive correlation (r=0.67, p<0.05) was found between the rolling velocity and the negative contribution of Mechanism 1. These results indicate that (a) the torque exerted by the batter resists the rolling and that (b) a higher rolling velocity is attained by batters who exert a smaller resistive torque on the bat than those who exert a larger torque. On the other hand, no correlation (r=0.09) was found between the rolling velocity and positive contribution of mechanism 2. Theseˆndings suggest that the batter makes an active eŠort to resist rolling, and that the amount of resistive torque exerted by the batter is the primary reason for the inter-individual diŠerence in rolling velocity attained at the instant of ball impact. As the resistive torque is likely to be exerted by the nobside hand in the form of pronation torque (Ae et al. 2014) and the pronation causes lowering of the bat-head (increasing nutation angle), a reduction of the pronation torque should decrease the resistive torque acting on the bat, helping to attain a high rolling velocity. In fact, we observed a greater deceleration of nutation velocity in the fast-rolling group than in the slowrolling group (p<0.05). To attain the high rolling velocity, therefore, we suggest that batters should aim to build up the nutation velocity of the bat until about 50 ms before ball impact, and then vigorously decelerate it immediately before ball impact.
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