Measurement of aerodynamic force and moment acting on a javelin using a magnetic suspension and balance system.

The rules governing the dimensions of the Javelin were substantially changed in 1986. It was considered that this new design guaranteed there was zero pitching moment at 0° angle of attack and that the pitching moment decreased (became negative) with increasing angle of attack. The objective of this study is to investigate if the pitching moment remains always negative (nose-down rotation). To measure accurate aerodynamic forces acting on a Javelin, the world's largest 1 m magnetic suspension and balance system was used. The magnetic suspension and balance system was able to measure aerodynamic forces without support interference in the wind tunnel. In addition, computational fluid dynamics were carried out to estimate the pitching moment coefficients. It was found that the pitching moment coefficient of a commercially available Javelin becomes positive (nose-up rotation) at lower angles of attack, less than 12°. The pitching moment becomes positive if the upstream side of the center of gravity receives more inflow than the downstream side. This situation can be attained by, for example, increasing the thickness of the upstream side when compared with that of the downstream side.

Motion Analysis Focusing on Rotational Movements of Professional Female Baseball Pitchers: Comparison with Male University Baseball Pitchers.

PURPOSE: The purpose of this study was to compare pitching motion of the professional female baseball pitchers with the male university baseball pitchers focused on the pelvic and thoracic movements. SUBJECTS AND METHODS: The participants were 15 healthy professional female baseball pitchers (11 right-handers and 4 left-handers; age, 21.7 ± 3.2 years; height, 162.5 ± 5.1 cm; weight, 59.0 ± 6.6 kg) and 14 healthy male university baseball pitchers (12 right-handers and 2 left-handers; age, 19.9 ± 0.8 years; height, 176.4 ± 3.0 cm; body mass, 73.1 ± 3.0 kg). Throwing motion was captured by three-dimensional motion analysis system. Kinematic data of the lead hip, pelvis, thorax, and dominant shoulder were collected and the joint angle at maximum external rotation phase and ball release phase were compared. RESULTS: The female baseball pitchers rotated pelvis and thorax more than the male at the maximum external rotation phase and ball release phase (p < 0.05). At the same, the pelvis and thorax of the female baseball pitchers were tilted significantly closer to horizontal plane than the male (p < 0.05). The pelvis and thorax of the male baseball pitchers was tilted to non-dominant lateral side. CONCLUSIONS: The results of this study indicate that the pelvic and thoracic movements of the professional female baseball pitchers was different from male university pitchers.

Motion analysis of operating a balance exercise assist robot system during forward and backward movements.

[Purpose] Stand-and-ride personal mobility devices controlled by movements of the user's center of gravity are used for balance training. We aimed to describe the physical activity required to operate this type of mobility device. [Participants and Methods] Eleven healthy males performed the following tasks: 1) moving their center of gravity forward or backward while standing on the floor (control task) and, 2) moving the mobility device forward or backward by moving their center of gravity (experimental task). [Results] We observed that the displacement of the center of gravity and the center of pressure, as well as angular displacements of the hips and knee joints, and maximum muscle activities of the biceps femoris, the medial head of the gastrocnemius and peroneus longus muscles were lesser during the experimental than during the control task. The distance moved by the device was significantly greater than the displacement of the user's center of gravity during the experimental task. [Conclusion] We observed that moving the device forward or backward required lesser physical activity than that required to shift the user's center of gravity forward or backward while standing on the floor. Additionally, we observed that even a small displacement of the user's center of gravity produced a large displacement of the device. We concluded that during balance training, the greater and more easily perceived movement of the mobility device would provide helpful feedback to the user.

Relationship Between Physical Fitness at the End of Preseason and the Inseason Game Performance in Japanese Female Professional Baseball Players.

Watanabe, Y, Yamada, Y, Yoshida, T, Matsui, T, Seo, K, Azuma, Y, Hiramoto, M, Miura, Y, Fukushima, H, Shimazu, A, Eto, T, Saotome, H, Kida, N, and Morihara, T. Relationship between physical fitness at the end of preseason and the inseason game performance in Japanese female professional baseball players. J Strength Cond Res 33(6): 1580-1588, 2019-This study examined anthropometric and fitness profiles of Japanese female professional baseball players and investigated the relationship between players' physical fitness and inseason game performance. Fifty-seven players who were registered in the Japan Women's Baseball League (JWBL) participated. Height, body mass, grip strength, back strength, knee extension and flexion strength, hamstring extensibility, vertical jump height, and horizontal jump distance were measured at preseason (February and March) in 2013. Game performance during the 2013 season (March-November) was obtained from official JWBL statistics. Vertical jump height showed significant positive correlations with individual performance records (e.g., total bases [r = 0.551], slugging percentage [r = 0.459], and stolen bases [r = 0.442]). Similar relationships were observed between horizontal jump distance and performance statistics in most cases. By contrast, grip, back, and lower-limb strength, as well as hamstring extensibility were not significantly correlated with game performance. Stepwise regression analysis selected vertical jump height as an independent variable, significantly correlating with several game performance measures (e.g., total bases: adjusted R = 0.257). Also, vertical jump height and body mass index were identified as independent variables significantly associated with stolen bases (adjusted R = 0.251). Maximal jump performance, rather than simple isometric muscle strength or flexibility, is a good performance test that can be used at the end of preseason to predict inseason batting and stolen base performance. Our findings demonstrate the importance of constructing preseason training programs to enhance lower-limb muscular power that is linked to successful inseason performance in female baseball players.

Hip, Trunk, and Shoulder Rotational Range of Motion in Healthy Japanese Youth and High-school Baseball Pitchers.

OBJECTIVE: The rotational range of motion (ROM) in the upper extremities, trunk, and lower extremities is important for throwing motion. However, unlike for the shoulders, the differences relating to age and throwing-side in trunk and lower extremity ROMs in baseball pitchers are unknown. This study examined the effects of age and dominance on the ROMs of the trunk and upper and lower extremities. METHODS: The study included 356 young baseball pitchers aged 9-17 years who participated in off-season baseball camps. The subjects comprised 155 youth pitchers (aged 9-14 years) and 201 high-school pitchers (aged 15-17 years) who were able to throw at full force without pain. The neck, shoulder, trunk, and hip rotational ROMs on the dominant and non-dominant side were measured by well-trained physical therapists. The differences between throwing sides and between age groups were examined using two-way analysis of variance. RESULTS: Shoulder external rotation on the dominant side was greater than that on the non-dominant side. Shoulder external and internal rotational ROMs were maintained regardless of age, whereas the trunk rotational ROM significantly increased with age. CONCLUSIONS: The effects of age and dominance on ROMs of the neck, trunk, and upper and lower extremities in Japanese youth and high-school baseball pitchers were clarified. These data could be used as a specific reference and as target values for the rehabilitation of throwing injuries in young athletes.

Visualization of air flow around soccer ball using a particle image velocimetry.

A traditional soccer ball is constructed using 32 pentagonal and hexagonal panels. In recent years, however, the likes of the Teamgeist and Jabulani balls, constructed from 14 and 8 panels, respectively, have entered the field, marking a significant departure from conventionality in terms of shape and design. Moreover, the recently introduced Brazuca ball features a new 6-panel design and has already been adopted by many soccer leagues. However, the shapes of the constituent panels of these balls differ substantially from those of conventional balls. Therefore, this study set out to investigate the flight and aerodynamic characteristics of different orientations of the soccer ball, which is constructed from panels of different shapes. A wind tunnel test showed substantial differences in the aerodynamic forces acting on the ball, depending on its orientation. Substantial differences were also observed in the aerodynamic forces acting on the ball in different directions, corresponding to its orientation and rotation. Moreover, two-dimensional particle image velocimetry (2D-PIV) measurements showed that the boundary separation varies depending on the orientation of the ball. Based on these results, we can conclude that the shape of the panels of a soccer ball substantially affects its flight trajectory.

Sixty six-month follow-up of muscle power and respiratory function in a case with adult-type Pompe disease treated with enzyme replacement therapy.

We report a patient with adult-type Pompe disease treated with enzyme replacement therapy (ERT) for 5.5 years. We evaluated pulmonary function and muscle strength using 6-minute walk test, manual muscle test, and dynamometer-based measurement. The long-term ERT resulted in a substantial improvement in the pulmonary function and a possible stabilization followed by mild deterioration in muscle power measured by dynamometer and 6-minute walk test. Our data may rationalize the long-term use of ERT for adult-type Pompe disease in terms of maintaining pulmonary function.

Aerodynamic drag of modern soccer balls.

Soccer balls such as the Adidas Roteiro that have been used in soccer tournaments thus far had 32 pentagonal and hexagonal panels. Recently, the Adidas Teamgeist II and Adidas Jabulani, respectively having 14 and 8 panels, have been used at tournaments; the aerodynamic characteristics of these balls have not yet been verified. Now, the Adidas Tango 12, having 32 panels, has been developed for use at tournaments; therefore, it is necessary to understand its aerodynamic characteristics. Through a wind tunnel test and ball trajectory simulations, this study shows that the aerodynamic resistance of the new 32-panel soccer ball is larger in the high-speed region and lower in the middle-speed region than that of the previous 14- and 8-panel balls. The critical Reynolds number of the Roteiro, Teamgeist II, Jabulani, and Tango 12 was ~2.2 × 10(5) (drag coefficient, C d ≈ 0.12), ~2.8 × 10(5) (C d ≈ 0.13), ~3.3 × 10(5) (C d ≈ 0.13), and ~2.4 × 10(5) (C d ≈ 0.15), respectively. The flight trajectory simulation suggested that the Tango 12, one of the newest soccer balls, has less air resistance in the medium-speed region than the Jabulani and can thus easily acquire large initial velocity in this region. It is considered that the critical Reynolds number of a soccer ball, as considered within the scope of this experiment, depends on the extended total distance of the panel bonds rather than the small designs on the panel surfaces.

Whole-body and segmental muscle volume are associated with ball velocity in high school baseball pitchers.

The aim of the study was to examine the relationship between pitching ball velocity and segmental (trunk, upper arm, forearm, upper leg, and lower leg) and whole-body muscle volume (MV) in high school baseball pitchers. Forty-seven male high school pitchers (40 right-handers and seven left-handers; age, 16.2 ± 0.7 years; stature, 173.6 ± 4.9 cm; mass, 65.0 ± 6.8 kg, years of baseball experience, 7.5 ± 1.8 years; maximum pitching ball velocity, 119.0 ± 9.0 km/hour) participated in the study. Segmental and whole-body MV were measured using segmental bioelectrical impedance analysis. Maximum ball velocity was measured with a sports radar gun. The MV of the dominant arm was significantly larger than the MV of the non-dominant arm (P < 0.001). There was no difference in MV between the dominant and non-dominant legs. Whole-body MV was significantly correlated with ball velocity (r = 0.412, P < 0.01). Trunk MV was not correlated with ball velocity, but the MV for both lower legs, and the dominant upper leg, upper arm, and forearm were significantly correlated with ball velocity (P < 0.05). The results were not affected by age or years of baseball experience. Whole-body and segmental MV are associated with ball velocity in high school baseball pitchers. However, the contribution of the muscle mass on pitching ball velocity is limited, thus other fundamental factors (ie, pitching skill) are also important.

[Gait disturbances related to dysfunction of the cerebral cortex and basal ganglia].

This review aimed to characterize the gait disturbances in Parkinson disease (PD) and highlight how a rehabilitation program would affect the care of patients with PD. The typical PD gait is a type of hypokinetic gait characterized by reduced stride length and velocity; shortening of the swing phase; and increase in the stance phase, double-limb support duration, and cadence rate. In the advanced phase of PD, start hesitation, shuffling and festinating gait, propulsion, and freezing of gait (FOG) become remarkable. Notably, in PD, attention may influence gait control, and sensory cueing may improve the stride length. Our study on gait impairment in PD by using a three-dimensional motion analysis system revealed that the stride length and walking speed decreased, but there was no change in cadence. The decreased stride length was due to reduction in the range of movement at the leg and pelvic joints. A 4-week physical rehabilitation program for PD improved the stride length and walking speed;this was achieved by increasing the range of movement of at the leg and pelvic joints. We also assessed the effects of a rehabilitation program for patients with PD who experienced FOG. Although the lower limb function was more impaired in patients with PD and FOG than in those with PD without FOG, the rehabilitation program was effective even for patients with PD and FOG. FOG might be associated with functional impairment of the lower limb as well as dysfunction of the fronto-basal ganglia circuit. We also reported 3 cases of camptocormia (bent spine syndrome) with autonomic dysfunction and rapid eye movement (REM) sleep behavior disorders (RBD) and compared their symptoms with those reported elsewhere. We think that the pedunculopontine nuclear area may control the postural muscle tone and locomotion in PD. On the basis of the results of our rehabilitation programs, we speculate that physical modalities may modify synaptic plasticity by utilizing the cerebellar and/or afferent sensory system. These alternative systems are believed to be functionally intact in patients with PD.