American football is associated with a high risk of cervical injuries. In order to prevent these injuries, head acceleration during head impacts is currently being studied, but no studies have examined the effects on the neck. We aimed to examine the effects of head impact kinematics (the number of head impacts, maximum head linear acceleration [LA], and maximum head angular acceleration [AA]) on cervical vertebral translation (VT) in collegiate American football players over a one-year period. Twenty-two players (5 linemen and 17 skill players) who belonged to T university in the Kantoh Collegiate American Football Association Division 2. We examined the relationship between the total number of head impact kinematics over a 1-year period and the amount of cervical vertebral translation as measured by a mouth guard with a 6-axis accelerometer. The total number of head impacts of subjects was 12,368. For skill players, the 4th cervical vertebral movement distance was significantly correlated with the maximum AA (r = 0.49, P = 0.04) and also with the maximum LA (r = 0.48, P = 0.05). In Japanese collegiate American football players, it was suggested that the repeated head impacts with large maximum LA and AA generated in the head affected the amount of the 4th cervical vertebral translation. In particular, skill players were affected, so they need to develop safer tackle skills even when tackling at high speed. This may result in a decrease in acceleration during head impact, leading to a decrease in the load on the cervical spine.

This cross-sectional study aimed to examine the independent associations of objectively measured moderate-to-vigorous physical activity (MVPA), sedentary time (ST), and cardiorespiratory fitness (CRF) with metabolic syndrome (MetS) among industrial workers. A total of 536 Japanese male industrial workers aged 35–59 years were included in the study. MetS was defined using the 2009 Joint Interim Statement definitions. ST and MVPA were measured using a triaxial accelerometer. Maximal oxygen uptake (VO₂max) was estimated through the bicycle ergometer-based submaximal aerobic fitness test. Logistic regression models were used to examine the associations of ST, MVPA, and VO₂max with MetS. The mean age was 48.6 (8.1) years, and the prevalence of MetS was 12.7%. After adjusting for covariates, the odds ratios (OR) and 95% confidence intervals (CI) of prevalent MetS for the highest and middle tertiles of MVPA were 0.22 (95% CI 0.09–0.53) and 0.89 (95% CI 0.51–1.57), respectively. The OR of the prevalent MetS for the highest and middle tertiles of VO₂max were 0.23 (95% CI 0.11–0.49) and 0.49 (95% CI 0.27–0.90), respectively. However, no significant association was found between ST and prevalence of MetS. The associations for MVPA and VO₂max did not change materially after mutual adjustment for ST, MVPA, and/or VO₂max. In conclusion, higher levels of both MVPA and CRF were independently associated with a lower likelihood of MetS among Japanese male industrial workers.

Evaluating range of motion (ROM) using several joints is essential for rehabilitating throwing injuries. We used multivariate analysis to elucidate the ROM patterns in baseball pitchers. This cross-sectional study measured the variable ROM in the upper extremities, trunk, and lower extremities. High school baseball pitchers participated (N = 121). Factor analysis of ROM was performed using the maximum likelihood method. We analyzed the characteristics of pitchers with positive findings by classifying all players using cluster analysis (Ward’s method). Factor analysis showed a seven-factor solution was shown to be appropriate. Cluster analysis indicated that we could divide the players into three clusters that we named according to their characteristics and ROM: Cluster A: “Low flexibility” type, Cluster B: “High rotation” type, and Cluster C: “Poor rotation” type. The results indicated that most positive players were in Cluster A (46.4%). Players in Cluster A had lower ROM in the trunk, hip rotation, and SLR (straight leg raise) test than the other groups. This is the first study to identify the patterns of ROM in high school baseball pitchers with positive findings. These results are useful for conditioning baseball players.

Esports players often use the fingers on their left hand to produce quick key hits on keyboards. It is unknown whether such hits can be a burden on fingers or cause overuse injuries. Numerous studies have focused on key hits; however, those studies have primarily focused on speed. Therefore, in this study, we evaluate rapid key hits using a combination of input data, video data, and surface electromyography (EMG) for fingers that are not accustomed to moving rapidly. Ten male subjects were asked to repeatedly hit the same key on a keyboard quickly using their left ring finger for 30 s. The results indicated that the input speed of a continuous single hit (6.48 Hz for 0–5 s) decreased over time (5.02 Hz for 25–30 s). Matching input and surface EMG data revealed movement with muscle activity, but without an input, that is, a miss-hit. Video results demonstrated that some subjects hit in a flexible manner, while others hit with unnatural form. Until now, there was only data on whether the speed was fast or slow for rapid key hits. A combined analysis of input data, EMG data, and video data can be used to evaluate miss-hits and hitting form.