Journal of Physical Fitness and Sports Medicine

Official journal of the Japanese Society Physical Fitness and Sports Medicine

Online First

The Journal of Physical Fitness and Sports Medicine (JPFSM)

[Volume 12, Number 1 January 25, 2023]

Regular Article

Umeoka, S., et al. : Effect of repeated head impacts on the amount of the cervical vertebral translation among university American football players
Received: April 15, 2022 / Accepted: September 5, 2022

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 in collegiate American football players over a one-year period. 22 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 kinematics over a year period and the amount of the cervical vertebral translation as measured by a mouth guard with a 6-axis accelerometer. The total number of head impacts of the 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 university 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 acquire accurate tackle skills even with a tackle with speed. This may result in a decrease in acceleration during head impact, leading to a decrease in the load on the cervical spine.

Yagi, K., et al. : Associations of sedentary time, physical activity, and cardiorespiratory fitness with metabolic syndrome in Japanese industrial workers: The Toyota Motor Corporation Physical Activity and Fitness Study
Received: April 12, 2022 / Accepted: October 18, 2022

Objectives: 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. Methods: 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 (VO2 max) was estimated through the bicycle ergometer-based submaximal aerobic fitness test. Logistic regression models were used to examine the associations of ST, MVPA, and VO2 max with MetS. Results: 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 VO2 max 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 VO2 max did not change materially after mutual adjustment for ST, MVPA, and/or VO2 max. Conclusions: Higher levels of both MVPA and CRF were independently associated with a lower likelihood of MetS among Japanese male industrial workers.

Hiramoto, M., et al. : Range of motion patterning in trunk and upper and lower extremities of high school baseball pitchers
Received: May 6, 2022 / Accepted: October 18, 2022

Introduction: Evaluating different range of motion using several joints is essential for rehabilitating throwing injuries. We used multivariate analysis to elucidate the range of motion patterns in baseball pitchers. Methods: This cross-sectional study measured the 18 variable ranges of motions in the upper extremities, the trunk, and the 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 method). Results: 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 range of motion: 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 range of motion in the trunk, hip rotation, and SLR (Straight Leg Raising) than the other groups. Conclusions: This is the first study to identify the patterns of range of motions in high school baseball pitchers with positive findings. These results are useful for conditioning baseball players.

Okinaka, M., et al. : Evaluation of the performance of key hits using input data, electromyography, and video analysis
Received: June 30, 2022 / Accepted: October 21, 2022

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 the 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. 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 supplely while others hit with unnatural form. Until now, there was only a measure of 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.

[Volume 12, Number 2 March 25, 2023]

Regular Article

Kijima, H., et al. : Characteristics of adolescent athletes with pain during sports activities: Evaluation of flexibility using ultrasound elastography
Received: January 27, 2022 / Accepted: November 22, 2022

Medical checkups for adolescent athletes aim to prevent or detect sports injuries and manage them before they hamper future sports activities and daily life. However, effective items for evaluation, as well as the areas of intervention to prevent sports injuries, remain unclear. We aimed to clarify the checkup items and intervention areas to prevent sports injuries in adolescent athletes. This is a cross-sectional observational study that investigated the presence or absence of pain in adolescent athletes and the associated factors at the time of checkup. We examined 301 junior high school athletes; joint laxity, range of motion, finger-floor distance, heel–buttock distance, straight leg raising angle, too many toes sign, and presence or absence of low back pain during lumbar extension were investigated. Additionally, after confirming the developmental stage of the tibial tuberosity using ultrasonography, ultrasound elastography was used to quantify the elasticity of the quadriceps femoris; items related to pain during sports activities were extracted. Items related to pain included the too many toes sign, low back pain during lumbar extension, and elasticity of the quadriceps femoris. Athletes with a positive ‘too many toes’ sign are less likely to experience pain; conversely, the harder the quadriceps femoris, the more likely they were to experience pain. Medical checkups focusing on these items are effective for adolescent athletes who are prone to knee pain.