Masaaki Sugita

Objective: Stress fractures (SF), menstrual dysfunction (MD), and eating disorders (ED) in young athletes are important issues. We conducted this study to determine the frequency of SF, MD, and ED experienced by high school track and field athletes in Japan and to understand the factors associated with them. Materials and Methods: A cross-sectional study of 1199 high level high school track and field athletes (608 males and 591 females) who participated in a selective training camp held by the Japan Association of Athletics Federations. Results: Approximately one in four male and female athletes self-reported SF. Moreover, we identified the length of the practice time per week and the event (sprinting, middle-distance, jumping, and combined) as relevant factors. Approximately one in three female athletes self-reported MD history, with those participating in long-distance events experiencing it significantly more frequently than those participants in sprinting, throwing, and jumping events. Furthermore, we identified ED history and long-distance events as MD history-related factors. ED history was self-reported at low frequency without gender difference, and long-distance was significantly more frequently reported than sprinting and jumping. Conclusions: About a quarter of Japanese high school track and field athletes experience SF, and about a third of the females experience MD. The association of these with athletic events, training time, and ED should be considered.

Sweat contains electrolytes (minerals), therefore, it is necessary to consider its loss through sweat in the fluid replacement strategy in sports. The purpose of this study was to compare the concentration of components in sweat, such as electrolytes (minerals), when endurance exercise is performed in hot and neutral thermal environments. Eight men cycled for 60 min at 55% VO₂peak under two envitonment conditions: a hot environment (WetBulb Globe Temperature (WBGT): 29.0±0.2℃; Heat) and a neutral thermal environment (WBGT: 20.5±0.2℃; Con). During exercise, sweat loss, core temperature, and heart rate (HR) were measured, and sweat from the chest, back, and thigh was collected. The core temperature, sweat loss, and HR increased significantly in Heat. The sweat electrolyte concentration was significantly higher in Heat than in Con only for Na. Regarding the amount of electrolyte loss from sweat, Na and K showed a significantly higher value than Con in Heat in comparison of each region, and the total loss amount of three regions in Cu also had a significantly higher value than Con in Heat. In addition, there was no difference in the concentration of Ca and Cu between the regions, but there was a significant difference in the amount of loss. It was concluded that even if there was no difference in the electrolyte concentration in sweat, the amount of electrolyte loss increased in K and Cu in a hot environment, and that there was a site difference in the amount of loss in Ca and Cu.

The effect of an amino acid mixture on the recovery from muscle fatigue after eccentric exercise (ECEX) training was examined in twenty-two male college students. The administration of 5.6 g of the amino acid mixture twice daily resulted faster recovery of muscle strength than that with a placebo. The oral administration of the amino acid mixture was proved to effective for muscle strength recovery after the eccentric exercise.