ObjectivesThere is notable sex difference in the manner of locomotion, but researchers are yet to obtain the comprehensive information about the biomechanical difference in gait pattern between males and females. The present study aimed to investigate sex differences in plantar pressure distribution during self-paced walking using a cluster-based permutation approach.MethodPlantar pressure data were collected from 24 healthy males and 68 healthy females using a pressure-sensor footplate. Group comparisons were conducted for basic gait parameters as well as pressure-related metrics, including maximum force, peak pressure, and contact area size. Additionally, time-series characteristics of total force were compared between sexes. A cluster-based permutation test was used to identify spatial and temporal regions with significant sex differences in plantar pressure distribution at high resolution.ResultsAnalyses revealed that females exhibited shorter step durations and higher cadence compared to males, attributable in part to differences in the duration of the late stance phase. Females also demonstrated higher weight-normalized plantar pressures across most of the stance phase. Sex-specific differences in plantar pressure distribution were localized to the calcaneal and second metatarsal regions.ConclusionSpatially localized pattern of sex difference in the plantar pressure indicates that biomechanical factors may contribute to the sex difference in the incidence rates of clinical conditions such as stress fracture. There was also a hitherto unreported pattern of sex difference in the time-series of total force, that may be related to sex-specific strategy to keep a self-preferred walking speed.

Background/Objectives: In pole vaulting, the capacity to store elastic energy within the pole (E-pole) significantly influences performance. This study investigated the characteristics of E-pole storage by analyzing the box reaction force and vector angle. Methods: Eight male pole vaulters, including World Championships participants, were examined. A motion capture system (VICON) and force plates (Kistler) were used to measure the vector angle (angle between the compression force (CF) and box reaction force vectors) and horizontal velocity of the center of gravity (COG) (Vcogh). E-pole was calculated as the integral of the CF (estimated from the box reaction forces), and pole bending displacement. The relationships between each variable and the peak height of COG (HP) were assessed using Pearson's product-moment correlation coefficients. Results: HP correlated with Vcogh in the pole plant (PP) (r = 0.82) and E-pole (r = 0.94). Vaulters with a higher HP maintained a vector angle < 2 degrees between 20% and 80% of the pole bending phase, indicating closer directional alignment between the box reaction force vector and pole chord direction, whereas vaulters with lower HP exhibited larger vector angles (4-8 degrees), associated with a relative reduction in the axial component of force transmitted to the pole. Conclusions: A smaller vector angle effectively enhanced the CF, thereby increasing pole bending and promoting greater accumulation of E-pole. Therefore, maintaining a small vector angle may enable more effective force transmission along the pole chord, and vector angle characteristics and PP horizontal velocity may assist appropriate pole selection and training strategies to enhance elastic energy storage and performance.

OBJECTIVES This study compared the mechanical outputs and lower joint kinematics during rowing motion using fixed and slide-type rowing ergometers to clarify the slide type's characteristics. METHODS Junior rowers performed a simulated 2000m race pace under two ergometer conditions. Rowing motion was filmed by a high-speed video camera (200 fps) from right angles beside the subject and changes in Hip and knee joint angles were measured. Spatiotemporal parameters as well as force output from the handle and stretcher and joint angle kinematics at 500m spot calculated. RESULTS In the 2000m time trial, the two conditions showed no significant difference. However, significant differences were observed in the maximum stretcher force, with the slide-type rowing ergometer showing higher values than the fixed-type rowing ergometer. On the other hand, greater values in handle force were found for the fixed-type rowing ergometer than slide-type rowing ergometer greater. Greater rate of force development for the handle and stretcher were observed in the slide-type rowing ergometer condition. No significant differences were observed in angular changes between the two conditions, but knee and hip maximum angular accelerations were significantly higher in the slide-type rowing ergometer condition. Higher stretcher force in slide-type rowing ergometer at the beginning of the stroke is characterized as the influence of maximal angular acceleration in both knee and hip joint extensions, causing high rate of force development of handle and stretcher forces in the initial phase of the drive. As a result, the muscle groups including the biarticular muscles around hip and knee joints may work in coordination to exert significant force, a defining characteristic of the slide-type rowing ergometer. CONCLUSIONS The fix-type rowing can be used effectively to strengthen the maximum handle pull strength, mainly upper extremity. On the other hand, slide-type rowing can be used effectively to strengthen the maximum stretcher force as well as it’s rate of force development, which might be similar force output of lower extremity as performed during on-water rowing.

Background: Estimating race times for open-water swimming based on pool swimming times could be useful for talent identification and training optimisation. We aimed to compare the swimming speeds of the world’s top and other swimmers in the 2023 Aquatics Championship men’s 10 km OWS race. Methods: Sixty-five swimmers were divided into four groups: G1 (1st–10th positions), G2 (11st–30th positions), G3 (31st–47th positions), and G4 (48th–65th positions). Swimming speed, stroke frequency (SF), and stroke length (SL) for each lap (laps 1–6) were recorded. Critical speed (CS) was calculated from each participant’s personal best times in the 400, 800, and 1500 m freestyle events in the pool. Swimming speed against CS was calculated (%CS). Results: The top performance group (G1) maintained their swimming speed from beginning (lap 1, 1.53 m/s) to end (lap 6, 1.50 m/s), at 92.7 ± 1.9% of CS, characterised by longer SL (1.26 m) and lower SF (72.86 rpm). G3 and G4 were unable to maintain their swimming speed, which decreased from G3: 97.64 ± 1.62% and G4: 96.10 ± 1.96% of CS at lap 1 to G3: 88.39 ± 3.78% and G4: 85.13 ± 5.04% at lap 6. This reduction in swimming speed is consistent with the increased reliance on anaerobic metabolism reported in previous studies under similar conditions. Conclusions: Race pacing for maintaining speeds of 92%CS throughout the race could be an important resilient index in open-water swimming. %CS might be a useful index for estimating the athletic performance level in open-water swimming.

[Purpose] The purpose of this study was to examine the characteristics of standing posture with turnout in children. [Participants and Methods] Ten female preschool children and thirteen skilled female adult ballet dancers participated in the study. The standing postures in the parallel and the turnout in the sagittal plane were photographed, and the posture angle, ear-neck angle, and horizontal distance from the vertical line to the anatomical measurement point were measured. [Results] Compared to dancers, children showed larger posture angles and forward movement of the torso in the turnout position. [Conclusion] In the turnout position, the children exhibited postural forward tilt and large forward movement of the torso region, which was different from the adult dancers who showed a decrease in postural forward tilt angle and cervical extension. The results suggest that preschool children have difficulty in achieving a vertical posture due to weak muscle strength in the trunk and lower limbs.

[Purpose] The purpose of this study was to examine the effect of turnout on the standing and plier postures in the introductory stage of classical ballet instruction. [Participants and Methods] Thirteen female ballet dancers and thirteen females with no dance experience participated in this study. The standing and plier postures in parallel and turnout position were photographed in the sagittal plane, and the posture angle, ear-neck angle, pelvic angle, and horizontal distance from the vertical line to the anatomical measurement point were measured. [Results] Ballet dancers had more posterior tilt, cervical extension, and anterior aspect of the xiphoid process in the plier posture than non-dancers. [Conclusion] The results suggest that ballet dancers maintain vertical posture by segmental movement of the spine during turnout; therefore, we consider it effective to teach ballet dance beginners to improve spinal mobility and pelvic tilt movement.

Background] Recently, the effectiveness of hyperbaric oxygen exposure has been reported in various studies, there are also possible disadvantages associated with higher oxygen concentrations.One such disadvantage is the possibility of an increase in reactive oxygen species (ROS), which are believed to be involved in the development of oxygen toxicity.However, the details of biological reactions involving ROS induced by hyperbaric oxygen exposure are not yet clear.[Purpose] The purpose of this study was to investigate the effects of hyperbaric oxygen exposure under 1.3, 1.5, 1.7, and 1.9 absolute atmospheric pressure conditions on oxidation and antioxidant markers.[Methods] The subjects were six healthy young.The stayed room was a pressure-resistant unit.The set pressure conditions were 1.3, 1.5, 1.7, and 1.9 atmospheres.The time spent in the pressure-resistant unit consisted of pressurization duration + set pressure duration + decompression duration.The duration of stay at the setting pressure was 60 minutes.The items measured in this study were the d-ROMs test as an oxidative stress marker and the BAP test as an antioxidant marker.[Results and Discussion] As a result of hyperbaric oxygen exposure at 4 atmospheric pressure conditions, there were no statistically significant differences in oxidative stress marker values and antioxidant stress marker values pre-vs post-exposure.These results suggest that hyperbaric oxygen exposure under the conditions of this study has no effect on oxidative stress and antioxidant stress.

To verify the reliability of the precision of TRACKMAN measurements, we analyzed 3 types of serves (flat, slice, kick) and compared the results to values obtained with the 3D motion capture system (VICON). Positive linear strong correlations were observed in velocity calculated with TRACKMAN(x) and VICON(y) ; (r = 0.996, p<0.01), as well as number of ball spin; (r = 0.978, p<0.01). This suggests that ball velocity and the number of ball spin values calculated with TRACKMAN, can provide immediate feedback and is provides sufficient reliability and would be useful in training situations.

Biomechanical features of the handstand, one of the most fundamental skills required for artistic gymnastics events, have not been well documented. The purpose of this study was to clarify the kinematics and joint moment profiles during straight arm press to handstand in different highly skilled male gymnasts. Fifty-nine male gymnasts performed a straight arm press to handstand on a force platform and were judged on their performance by experienced certified judges. Subjects were divided into two groups (highly-skilled and less-skilled). Kinematic data were obtained using a video camera synchronized with force platform. Joint moments (wrist, shoulder, hip) during each straight arm press to handstand were calculated using the inverse dynamics solution. Larger shoulder flexion moments were observed in less-skilled compared with highly- skilled performers (at 3–59%, p < 0.001) while larger hip flexion moments were observed in highly- skilled performers at 52% ( p = 0.045) and 56% ( p = 0.048) and normalized time of straight arm press to handstand. Major differences between highly-skilled and less-skilled performers were observed in hip joint moment production as it shifted from extension to flexion from the leg horizontal position to the handstand position in highly-skilled gymnasts. Successful straight arm press to handstand techniques observed in highly-skilled performers were characterized as a more acute pike position at toe-off as well as hip flexor moments at latter phase of the straight arm press to handstand.

The purpose of this study was to create a standard motion model of a basketball set shot. Twenty-one male collegiate basketball players participated in three-dimensional data collection session (Vicon MX+, 250Hz), and the method proposed by Ae, et al. (2007) was used to create a standard motion model. The set shot motion in the standard motion model started with the shoulder flexion and hip extension in the downward phase, followed by the sequential motions of the knee, ankle, shoulder, elbow and wrist joints in the upward phase. Immediately before the ball release, the elbow and wrist joints were abruptly extended. The motion variation in the wrist, elbow and shoulder joints just before the ball release were small, implying there must be some commonality in these joint motions.

The aim of this study was to investigate the developmental characteristics of change of direction ability in junior and youth male soccer players from13-18 age, and to determine the influence of the basic abilities that constitute change of direction running in each age groups. Change of direction running was measured by laser measuring instrument system. First, based on the 0 m position, participant started to run from-10 m position, turned the change of direction at cutting line(5 m passed from 0 m position)and ran back to the 0 m position again. The results showed that the change of direction running time for 15-16 and 17-18 groups was significantly faster than 13-14 groups, but that the difference was other than cutting phase. Furthermore, the basic abilities that comprise change of direction running were found to differ with age. That is, sprint ability had a strong influence on change of direction running for 13-14 groups;however, as players grew older, cutting ability also came to have a strong influence in addition to sprint ability.

Weightlifters experiences high mechanical stresses in their lumbar region. The intervertebral disks act as shock absorbers between each of the vertebrae in the spinal column. The disks of weightlifters may be injured by repetitive overload during weightlifting maneuvers. Previous studies have shown that excessive trunk rotation is a major risk factor for lumbar intervertebral disk degeneration (LIDD) in athletes. Although trunk rotation is not included in most weightlifting maneuvers, we hypothesized that there would be a high incidence of LIDD in collegiate weightlifters. PURPOSE: The purpose of this study was to examine the prevalence of LIDD in collegiate weightlifters. We also investigated possible risk factors for LIDD, except for excessive trunk rotation. METHODS: Forty Japanese collegiate weightlifters (25 men and 15 women; age, 19.6±1.1years; starting age, 15.1±0.9years; height, 164.7±8.0cm; weight, 71.9±14.kg). LIDD were evaluated using T2-weighted magnetic resonance images. Pfirrmann’s classification was used to define LIDD and classify the subjects into either the LIDD group or the non-LIDD group. We also investigated physical characteristics such as body composition (height, weight, muscle mass, fat mass), joint range of motion (thoracic, lumbar, and hip), and lumbosacral alignment (lumbar angle, sacral angle, and lumbosacral angle). Student’s t-test and logistic regression were used for statistical analyses. RESULTS: The prevalence of LIDD among weightlifters was 55.0%(22/40). Weight(77.3±16.40 vs. 65.7±10.24, p=0.02), fat mass(18.5±8.07 vs. 12.5±4.15, p=0.07), and body mass index(27.7±4.78 vs. 24.71±2.10, p=0.02) in the LIDD group were significantly higher than those in the non-LIDD group. Hip flexion angle (left: 121.5±10.10 vs. 126.9±6.15, p=0.05; right: 121.9±8.00 vs.127.9±7.06, p=0.04) and lumbar angle(18.3±6.04 vs. 24.2±4.65, p=0.01) were lower in the LIDD group compared to the non-LIDD group. By using logistic regression analysis including sex differences, lumbar angle was found to be a significant independent variable for LIDD (odds ratio, 1.34; 95%confidence interval 1.08-1.67, p=0.01). CONCLUSION: A high incidence of LIDD was observed in Japanese collegiate weightlifters. Lumbar angle is a possible risk factor.

Para verificar la confiabilidad de la precisión de las mediciones realizadas con TRACKMAN analizamos 3 tipos de servicio (Plano, Cortado, con Kick), y comparamos los resultados con los valores obtenidos con el sistema de captura del movimiento en 3D (VICON). Se observaron fuertes correlaciones lineales positivas en velocidad, calculadas con TRACKMAN (x) y VICON (y); (r = 0.996, p<0.01), igual que la cantidad de efecto de la pelota; (r = 0.978, p<0.01). Esto sugiere que la velocidad y la cantidad de los valores de efecto de la pelota calculados con TRACKMAN, que permiten proporcionar retroalimentación inmediata, son suficientes para la confiabilidad y serían útiles en situaciones de entrenamiento.