The purpose of this study was to examine weight loss effects on immune function in judo athletes. Six elite male Japanese judo athletes (20.3 ± 0.4 years) were enrolled in this study. They completed usual weight loss programs during 2 weeks preceding an actual competition. Subjects noted the appearance of upper-respiratory tract infection (URTI) symptoms during the study period. Blood samples were obtained at 40 (baseline period: BL) and 3 (weight loss period: WL) days before and 1 day after the competition (AC). The CD3, CD4, CD8, CD56CD3, CD28CD4, CD28CD8, and Toll-like-receptor-4 (TLR-4) CD14 cells were counted by using flow cytometer analysis. The 6 subjects reported 1 headache, 3 runny nose conditions, and 1 coughing instance during the WL. The CD3, CD4, CD8, and CD28CD4 cell counts were significantly lower at WL than at BL (p ≤ 0.05); they reverted to the baseline value at AC. The TLR-4CD14 cells were significantly fewer at WL (p ≤ 0.05); they remained fewer than they had been at BL, even at AC. These results suggest that 2 weeks of weight loss before a competition can impair cell-mediated immune function and induce high susceptibility to URTI in judo athletes. Coaches, support staff, and athletes should monitor athletes' weight loss, hydration status, appearance of URTI symptoms, and immunocompetence such as lymphocytes and monocytes to prevent the physical condition from becoming worse.

The purpose of this study was to extract current issues associated with the understanding of tackling techniques taught by college football coaches in Japan. The goal was to acquire fundamental information for a coaching method that would promote safe and effective tackling techniques. A total of 99 college football coaches from Japan (mean age 36.7±0.5 years) took part in the study. A questionnaire was conducted in order to understand key points that were considered important in their coaching methods. The results and observations can be summarized as follows. 1. Tackling techniques taught by football coaches in Japan often lead to concussions. This is due to coaching methods that focus heavily on tackling techniques with high concussion risks, and placing no importance on HUT-based tackling. In addition, their understanding of the "Hit" phase and "HUT" varies, leading to a greater possibility of teaching tackling with a high risk of concussion. 2. Regardless of factors such as age, the position taken as an active player, the instructor's income, and coaching qualifications, coaches who do not have much player or coach experience have an increased tendency to teach tackling techniques associated with high risks of concussion and injury. 3. In order to prevent concussions and promote safer tackling coaching in Japan, it is crucial for coaches who have little experience in playing or coaching to have access to appropriate information and education opportunities, and for coach certification programs to be improved.

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