This study aimed to assess kinematic and kinetic changes in front crawl with various stroke frequency (SF) conditions to investigate why swimming velocity (SV) does not increase above a certain SF (SFmax). Eight male swimmers performed 20 m front crawl four times. The first trial involved maximal effort, whereas SF was controlled during the next three trials. The instructed SFs were 100 (T100%), 110 (T110%), and 120% (T120%) of the SFmax. Through pressure measurement and underwater motion analysis, hand propulsive force (calculated by the difference between the palm and dorsal pressure value and the hand area) and the angle of attack of the hand were quantified, and differences between trials were assessed by a repeated-measures ANOVA. There was no difference in SV between the conditions, while the angle of attack during the latter half of the underwater stroke at T120% was smaller by 25.7% compared with T100% (p = 0.007). The lower angle of attack induced a lower pressure value on the palm that consequently caused a smaller hand propulsive force at T120% than T100% (p = 0.026).Therefore, the decrease in the angle of attack must be minimised to maintain the hand propulsive force.
The purpose of the two studies was to investigate the relationships among student athletes’ identity and mental health during the COVID-19 pandemic. In addition, this study aimed to clarify the relationship between perceived social support from teammates and mental health in student-athletes. Two studies were conducted to investigate and clarify the mental health states of student-athletes in Japan during the COVID-19 pandemic. In Study 1, conducted in April 2020, the participants were 402 male student-athletes and we examined the relationships among student-athletes’ identity and mental health. The results of correlational analyses indicated significant negative correlations between the degree of student-athletes’ identity and depression and sports helplessness. In Study 2, conducted in March 2021, the participants were 135 male student-athletes and examined the relationship between perceived social support from teammates, student-athletes’ identity, and mental health. The results indicated a significant correlation between social support, student athletes’ identity, and mental health.
Through pressure measurement, this study aimed to clarify the effects of hand paddle use on pressure and force generation around the hand during the front crawl. Eight male swimmers performed two trials of front crawl swimming with maximal effort, once using only their hands and once aided by hand paddles. During trials, pressure sensors and underwater motion capture cameras were used together to analyze hand kinematics and pressure forces acting on the hand. Six pressure sensors were attached to the right hand, and pressure forces acting on the right hand were estimated by multiplying the areas and the pressure differences between the palm side and dorsal side of the hand. Acting directions of pressure forces were analyzed using a normal vector perpendicular to the hand, calculated from coordinates of the right hand. As a result, using hand paddles decreases pressure differences between the palm and dorsal sides of hand related to the magnitude of pressure force. However, no difference was found in the mean value of resultant pressure forces compared with using hands alone, because the large surface area of the hand paddle compensated the decreased pressure differences due to decreased hand velocity. In addition, when hand paddles were used, the component of the pressure force acting in propulsive direction was significantly higher. Thus, the ratio of forces acting in the propulsive direction was higher than without hand paddles. These results suggest that the training loads with hand paddles are not high even if the swimming velocities increase because the power generated by upper limb motion didn't increase.
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