The purpose of the present study was to examine characteristics of muscle anatomical cross-sectional area (CSA) for different regions from proximal to distal parts of each muscle of the hamstring muscles in high-level sprinters, and to examine the relationship with those and the sprint performance. The CSA of the semitendinosus (ST), semimembranosus (SM), biceps femoris long head (BFL) and biceps femoris short head (BFS) at the four different region of hamstring muscles for twenty sprinters (SPRINT) and twenty healthy male control subjects (CTRL) were measured by using B-mode ultrasonography. The measured regions were divided into four parts from proximal to distal parts (PRO1, PRO2, DIS2, DIS1). The results clearly showed that absolute CSA values in distal parts for all muscles together with PRO2 in ST were greater in SPRINT than in CTRL. When relative CSA values to the entire hamstrings muscles in each region were compared, only relative CSA at PRO1 in ST was greater in SPRINT than in CTRL, conversely, that at proximal regions in BFL and distal regions in BFS were smaller in SPRINT. In the relationships with sprint performance, the CSAs at PRO1 and PRO2 in ST and at PRO1 in SM were only related negatively. These results suggest that distal parts of hamstring muscles for SPRINT may be characteristics for sprint runners. However, the movements related to the specific hypertrophy (PRO1 and PRO2 in ST, PRO1in SM) may play important roles of the improvement of their sprint performance.
The purpose of this study was to investigate the consciousness among young people (n = 1016) on training body part(s), using a questionnaire-based survey showing participants a picture of a single-joint exercise. The participants were shown a picture of knee-extension exercise (KNEE-EXT), and were asked to identify the body part(s) they felt were being trained. On seeing the picture, more than 90% of the participants felt that KNEE-EXT can train the anterior thigh part. However, more than 90% of the participants who had no experience doing KNEE-EXT felt that the exercise trained not only the anterior thigh part but also other parts, including the trunk, the posterior thigh, and the upper limb. Among those participants who had performed KNEE-EXT without the experience of strength-training under professional supervision, approximately 80% felt that the exercise was appropriate to train not only the anterior thigh but also other parts. These results suggest that performing exercises by referring to only a picture may result in the individuals not properly understanding how the body part(s) should be trained during exercise, even in single-joint exercises. Appropriate supervision is of even greater importance especially for strength-training beginners. Furthermore, even among participants who had an experience of exercise under professional supervision, approximately 60% had a similar response. Therefore, to enhance the benefits of exercises, individuals (even those who have had experience in training under professional supervision) should always be instructed under appropriate supervision on the correct technique and knowledge about the exercises.
The purpose of this study was to clarify the aerobic fitness of triathletes comparing with long-distance runners with the same level of running performance. Thirteen male university endurance athletes were divided into two groups ; long-distance runners and triathletes. The subjects performed maximal and submaximal treadmill running test to assess their maximal oxygen uptake (VO2max) and running economy (RE). The VO2max (ml/kg/min) in triathletes was lower than that in the runners (p = 0.08, d = 1.18). The RE (ml/kg/km) in triathletes was higher than that in the runners (p = 0.05, d = 1.34). This study suggests that the difference of aerobic fitness between two homogeneous groups is caused by running form and the training with preceding exercise.
The purpose of this study was to examine the contribution of the location-tracking information to the energy expenditure during the soccer-based intermittent sprint run. Twenty-four young healthy men participated in the present investigation (1st experiment: 14 men, 2nd experiment 10 men). In the 1st experiment, the sprint runs were 12 times of the 10 m (SS10), or 6 times of the 20 m (SS20), or td 3 times of the 40 m (SS40). In the 2nd experiment, the sprint runs 15 times of the 10 m (SS), or 15 times of the 10 m of the sprint run with change of direction for 90, 135, 180 degrees (CD90, CD135 and CD180). All course of the experiment, the expired gas was analyzed using the portable gas analyzer. The running index including speed, acceleration, distance, were calculated at 15 Hz interval based on the location-tracking information using the portable global positioning system. The intermittent run with the straight sprint run expended significantly larger calorie compared with that without the straight sprint (p < 0.001). The intermittent run with the changes of direction expended significantly larger calorie compared with that without the changes of direction (p < 0.05). A multiple stepwise regression analysis revealed that body weight, the acceleration and the change of direction were significant determinants of the energy expenditure and accounted for 75% of the total variance. These results indicate that the magnitude of the acceleration is significant predictor for the energy expenditure of the intermittent exercise.
In Japan, Nordic walking (NW) has two style walking method. For one thing, the poles are used to push against the ground towards the back of the body (diagonal style: DIA). The other one, the poles put on forward and using like a cane (defensive style: DEF). This study aims to clarify differences between the two Nordic walking (NW) styles. The subjects were 12 community-dwelling middle-aged and older adults (mean age: 62.4 ± 7.8 years). All of subjects were tested to perform NW in both style for 12 minutes walking around the park. Walking distance, speed, heart rate (HR), energy expenditure (EE) and electromyogram (EMG) amplitude of the upper and lower limbs using surface EMG were assessed. A pole with a built-in load cell measured force used to push the pole into the ground (pole force), pole contact time, and pole impulse. Distances and speed in DIA was significantly higher than DEF. Significant difference in muscle activity was observed between DIA and DEF in the triceps brachii only. EE of DEF was significantly higher than DIA. Poling force and pole impulse in DIA was significantly higher than DEF. These results indicate that when prescribing NW for health promotion, it should be done according to each characteristic in DIA or DEF.
Although street dance quickly became popular in Japan, and the population of street dancers is increasing, there is limited information on injuries sustained during street dance in Japan. The purpose of this study was to investigate the epidemiology of injuries in street dancers in Japan. One hundred and ninety-five Japanese street dancers (92 intermediate, 35 advanced, and 68 expert dancers) participated in this study. A questionnaire survey concerning the injuries sustained during dancing was conducted over a 3-month period. The main results were: (1) Sixty-one dancers reported a total of 72 injuries, and injury rate was 0.56 per 1000 players-hours; (2) Ankle injuries accounted for 45.8% of the reported injuries; (3) Dancing proficiency level was related to the occurrence of injury, and the occurrence was significantly higher for the expert dancers; (4) The duration of warm-up was related to the occurrence of pains. These findings provide fundamental information that may contribute to the development of injury prevention in street dance.