Prediction models of the oxygen uptake (VO₂) from electromyograms (EMG) of the lower limb and respiratory muscles during an incremental exercise test were examined. Healthy male adults (n=15) underwent an incremental exercise test using a cycle ergometer. To predict the patterns of VO₂, we used a type of recurrent neural network, the long short-term memory. The measured patterns of VO₂ were used as training data for deep learning, and two prediction models as input values were set: a lower limb muscle model and a respiratory muscle model. In the lower limb muscle model, EMGs of the rectus femoris and vastus lateralis were input. In the respiratory muscle model, EMGs of the sternocleidomastoid and inspiratory time were input. The patterns of both the measured VO₂ and predicted VO₂ increased during the exercise test. The histogram showed a peak difference between the measured and predicted VO₂ of 0 and 0.5 mL/kg/min. The Bland-Altman plots for both models demonstrated that most of the data were distributed within the range of agreement. The root mean square error (RMSE) during the exercise period was 2.1 ± 0.7 mL/kg/min for the lower limb muscle model and 2.8 ± 1.1 mL/kg/min for the respiratory muscle model, and the RMSE increased with the increasing course of time. In the cycle ergometer task, each model enable the estimation of the pattern of the VO₂. Mild to moderate exercise intensity was suitable for the prediction of VO₂ patterns by electromyography.

Hyperkyphosis is one of the risk factors for medial elbow injuries in baseball players. The purpose of this study was to determine the prevalence of hyperkyphosis in high school baseball players (Experiment 1) and to investigate the acute effects of spine mat usage in improving hyperkyphosis in high school baseball players (Experiment 2). Experiment 1: A study of 142 high school baseball players was conducted. A Spinal Mouse® was used to measure the thoracic kyphosis angle (TKA) with participants in an upright position. Hyperkyphosis was defined as a TKA of >40° in this study. The results showed that the prevalence of hyperkyphosis was 20.4% (29/142). Experiment 2: The participants were 56 high-school baseball players. For the intervention, the participant was placed in a supine position on a bed, and a spine mat was inserted such that it adhered to the thoracic spine. The primary outcome variable was TKA measured in the upright position using a spinal mouse before and after intervention with a spine mat. Based on this evaluation, we assigned the participants to two groups: hyperkyphotic (n =18) and non-hyperkyphotic (n=38). There were significant differences in pre- and post-test TKA in both groups (hyperkyphotic group: pre-test 44.4±3.8°, post-test 39.9±4.6°, P < 0.01; non-hyperkyphotic: pre-test 31.8±5.7°, post-test 29.2±7.8°, P < 0.01). The results of this study indicate a high prevalence of hyperkyphosis in high school baseball players. In addition, using a spine mat may lead to an acute improvement in hyperkyphosis in high school baseball players.

The purpose of this study is to clarify psychological factors related to recovery from sports injuries in judo and track and field. A questionnaire survey was conducted with male and female university judo players (n=944) and track and field athletes (n=645), who were identified using the snowball sampling. The questionnaire included the following items; the state of sports injuries, individual traits, coping resources, health related issues, stress responses and emotional supports. The questionnaire was conducted twice within a one year interval. Responses of participants with sports injuries were analyzed in the first survey (judo: n=190, track and field: n=111). Psychological factors in the recovery group and the non-recovery group were compared between the first and second survey and between groups by a two-way repeated measures ANOVA. In judo, there was a main effect between the groups of interpersonal dependency, stress responses “irritability-anger” and health management confidence (p< .05). In addition, there was an interaction effect between acquired resilience and emotional support from coaches (p< .05). In track and field, there was a main effect between the groups of stress responses “depression-anxiety” and “helplessness”, and between the time point of interpersonal dependency (p< .05). The results of this study suggested that while there were similarities in psychological factors between judo and track and field, the effects differed based on the type of sport, and that measures appropriate to the type of sport were required for psychological support when returning to the sport.

It would be interesting to examine how characterize relationship among physical activity (PA), physical fitness (PF), and skeletal muscle (SM) characteristics in adolescents; however, it is not well understood how those parameters are related each other. The purpose of this study was to elucidate relationship among PA, PF, or SM in adolescents. Fifty-five male and female students (13.1 ± 0.8 years) engaged in this study and PA, PF, and SM characteristics were measured. Muscle thickness (MT) and echo intensity (EI) of the quadriceps femoris were measured based on transverse images of B-mode ultrasonography. PF tests consisted of 9 different tests such as hand grip strength, sit-ups or side-to-side jump, developed by the Ministry of Education, Culture, Sports, Science and Technology, were used to estimate functional properties of the students. Significant correlations were found between moderate and vigorous intensity PA time and the PF test score (r=0.61 to 0.64, p<0.01), and VPA and MT (r=0.47, p<0.05) or EI (r=-0.52, p<0.05) in boys. We also found significant correlations between VPA and hand grip strengt (r=0.36, p<0.05) and MT (r=0.57, p<0.001) in girls. These results suggest that longer moderate and vigorous intensity PA time a day may help development of physical fitness and skeletal muscle size in adolescents, especially, in boys.

This study aimed to discuss the relationship between the change of trunk muscle thickness and the stability of landing movement of volleyball players with jumper’s knee. We studied a total of 14 women volleyball players. They were classified into the JK group consisting of 7 players with jumper’s knee and the CON group consisting of 7 players without jumper’s knee. We measured the transverse abdominis (TrA), internal oblique (IO), and external oblique (EO) both at rest and in the plank position (PL) of the subjects, and figured out change rates of their muscle thicknesses by dividing the muscle thickness in the plank position by that at rest. We also measured flexion angle of trunk, hip, and knee at landing. We found that change rates of IO were significantly lower in the JK group than in the CON group (p<0.01), and that flexion angles of trunk was significantly greater in the JK group than in the CON group (p<0.01). In conclusion, our study clarified that players in the JK group have a lower change rate of trunk muscle contraction and increase the flexion angle. It also clarified that they make a compensatory movement by flexing knee joint and body truck to reduce the burden on knee joint.