Background Basketball is one of the most played sports in the world. However, only a few studies have examined the epidemiology of Japanese collegiate men’s basketball injuries. This study investigated the incidence of injury among Japanese collegiate men’s basketball from the 2013/2014 to the 2019/2020 seasons and identified unique patterns by comparing our data with the National Collegiate Athletic Association (NCAA) men’s basketball data. Methods Data from Japanese collegiate basketball teams of the Kanto Collegiate Basketball Federation Division I League during the 2013/2014 to 2019/2020 academic years (23 team-seasons) were used in this study. Injury rates per 1000 athlete exposures (AEs), injury proportions, and the injury rate ratio (IRR) were calculated according to the events, injury types, body parts, and common injury mechanisms. Injury rates were then compared with that from the time-loss injury data of the NCAA’s previous reports. Results In total, 480 injuries during 97,515 AEs were reported, leading to an injury rate of 4.92 per 1000 AEs (95% CI = 4.48–5.36). The overall injury rate was higher in Japan than in the NCAA ([2009/2010–2014/2015] IRR = 1.55, 95% CI = 1.39–1.73; [2014/2015–2018/2019] IRR = 1.64, 95% CI = 1.48–1.82). Lower extremity injuries occurred most frequently (73.5%). Ankle sprain was the most common injury in Japan, with higher injury rates than in the NCAA (IRR = 2.10; 95% CI = 1.72–2.57). The injury rate of concussion was lower in Japan than in the NCAA (IRR = 0.28; 95% CI = 0.14–0.55). Conclusions The rates of overall injury and ankle sprain were higher and that of concussion was lower in Japan than in the NCAA. These results suggested the existence of international differences in the pattern or features of injuries in basketball players.

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Background This study examines age-related changes in the quadriceps femoris (QF), subdivided into the vastus medialis oblique (VMO), vastus medialis (VM), rectus femoris (RF), vastus intermedius (VI) and vastus lateralis (VL) in basketball players. Subjects Seventy male basketball players were divided into four groups according to age (12-13, 14-15, 16-17, and 18-20 years). Methods Ultrasonography was used to measure muscle architecture of the VMO, VM, RF, VI and VL. We created cubic approximate expressions and calculated inflexion points to evaluate peak growth age of each muscle head. Results Significant interactions were observed for all QF parts (p < 0.01-0.001). Muscle thickness (MT) in all QF parts was significantly lower in 12-13-year olds than in 18-20-year olds (p < 0.01-0.001). Significant differences were recognised between 12-13 and 16-17-year olds in VM (p < 0.001), RF (p < 0.001) and VL (p = 0.007). MT was significantly lower in 14-15-year olds than in 16-17-year olds in the VM (p = 0.007) and RF (p = 0.026) and in 18-20 year olds in the VM (p < 0.001), RF (p = 0.036) and VI (p < 0.001). Peak growth age was estimated for each QF part (VMO, 155.0 months; VM, 187.8 months; RF, 212.2 months, VI, 188.9 months; VL, 181.1 months). Conclusion QF parts have different growth rates due to differing functions in each muscle head.

Abstract:Resisted sprint training (RST) affects sprint speed in the acceleration phase, but there is no research regarding this for in adolescents. This study investigated the effects of RST on sprint speed and ground reaction force (GRF) in high school baseball players. Subjects were assigned to the resisted sprint group (RSG, n=10, loading 20% body mass), or the normal sprint group (NSG, n=9, without loading) and trained three days per week for eight weeks. Sprint speed [0-5, 5-10, 10-15, 15-20 and 0-20 meters (m)] and GRF [peak propulsive/resultant force, (PFpro/ PFres); impulse, (I); and ratio of force applied onto the ground (RF)] measured at the right and left foot at the start, the first step of the left foot (L1st), 5 m and 10m were assessed before and after training. In the RSG, a significant interaction was found for sprint speed at 0-5 m (p=0.028) and increased after training (p<0.0001). The 15-20 m sprint speed increased significantly in the NSG after training (p=0.022). The 0-20 m sprint speed increased significantly in both groups after training (RSG, p=0.001; NSG, p=0.041). Significant interactions were found for PFpro (p=0.015) and RF (p=0.0002) at the L1st in the RSG. PFpro (p=0.005), PFres (p=0.038) and RF (p=0.0002) at L1st increased significantly in the RSG. RST increased sprint speed in the early part of the acceleration phase by improving force production but prevented the improvement of sprint speed over 15 m. Combining RST and sprint training without loading improved sprint speed in the acceleration phase.

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Purpose: To examine differences in resistance exercise-induced hormonal responses among young athletes according to their maturity levels. Materials and Methods: A total of 12 collegiate and 32 junior high school male athletes were enrolled. The junior high school participants were divided into pre–peak height velocity (PHV) and post-PHV groups, according to their PHV ages. The salivary testosterone, cortisol, and human growth hormone levels were analyzed before (pre), immediately after (post), and at 15 minutes after performing body weight resistance exercise. Results: The testosterone levels were higher in the collegiate than in the junior high school group (P < .01) and increased after 15 minutes of exercise (P < .01). A significant decrease in the cortisol levels postexercise in the junior high school groups (P < .01) and an increase in the human growth hormone levels at 15 minutes after exercise in the post-PHV group were observed (P < .01). In the collegiate and post-PHV groups, the testosterone-to-cortisol ratio increased post and at 15 minutes after exercise (P < .01). The testosterone-to-cortisol ratio values were higher in the collegiate than in the post-PHV (at preexercise and at 15 min after [P < .01]) and pre-PHV groups (at all times [P < .01]). Conclusion: Exercise-induced acute hormonal responses to resistance exercise may depend on individuals’ maturity levels, even in those having the same age.

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The change-of-direction speed is an essential physical component in basketball. This study aimed to reveal the relationship between change-of-direction kinematics and the related motor abilities in basketball players. Motor abilities, including squat, sprint speed, vertical jump, and horizontal jump, were measured in 14 male collegiate basketball players. Furthermore, the change-of-direction speed and kinematics during the changeof-direction task, including the trunk lean angle and center-of-gravity height, were evaluated. Correlations between change-of-direction time and kinematics were assessed using the Pearson product-moment correlation coefficient. Once significant correlations were detected, orrelations between motor abilities and change-of-direction kinematics variables related to change-of-direction time were assessed using the Pearson productmoment correlation coefficient. There were significant correlations between change-ofdirection time and center-of-gravity height (r = 0.54), and trunk lean angle (r = -0.74).Moreover, there was a strong correlation (r = -0.53) between the center-of-gravity height and lower body strength. Improving lower muscle strength and change-of-direction kinematics may be necessary to enhance the overall change-of-direction performance.