Skeletal muscle has been recognized as an organ that imparts movement to the skeleton by contracting, creating motion and enabling movement. Recently, however, it has become clear that skeletal muscle contraction is linked to physiological functions other than movement, and it is being recognized that the role played by skeletal muscle is broader than previously imagined. Specifically, it covers a wide range of fields, including systemic metabolic regulation including glucose metabolism, the association to the multi-organ via secretions, and self-reconstruction through powerful regenerative ability. In addition, they are highly plastic in changing their own properties and structures according to the environment in which they are placed, which can have positive or negative effects on individual health and disease. We introduce the diverse properties of these skeletal muscles.

This study aimed to analyze the trunk movements of the white-handed gibbon and Japanese macaques to clarify the trunk control mechanism during bipedal walking in non-human primates. Axial rotation : The RoM (Range of motion) of the thoracic rotation relative to the pelvis did not differ between humans and other primates, suggesting that the trunk rotation mechanism is caused by the mechanical requirements of bipedal locomotion. Lateral list : This study revealed different lateral list patterns in the gibbon and Japanese macaques from the chimpanzees, suggesting interspecies differences in the postural control strategy of the trunk. Future anatomical studies using cadavers are needed to clarify its mechanise, although the vertebral coupling motion during bipedal walking was similar between humans and non-human primates.

Following an initial inversion ankle sprain, it is important to preventing the development of chronic ankle instability (CAI) and recurrence of sprains in copers while clarifying the kinematic characteristics of copers are critical. This study examined coordination among the forefoot, midfoot, and rearfoot during walking in coper and CAI groups. Ten participants in the control group, 12 in the coper group and 13 in the CAI group were measured while walking on a treadmill. The coupling angle which is a measure of coordination, was calculated and classified into four coordination patterns. The results showed that the coordination patterns of the coper group significantly decreased (p<0.05) as compared with the other two groups, where the rearfoot eversion motion and midfoot inversion motions were exhibited with rearfoot dominancy during the mid-stance phase. Coordination among the forefoot, midfoot and rearfoot in copers may be a strategy to prevent recurrence of sprains.

Ball play requires predicting the ball’s future location and moving there quickly. We investigated the association among capacities in locomotion, reaction time, approach direction of preschoolers (N=70) for an interception task, and ball-touch numbers in soccer play activities. In the interception task, we asked the children to chase and catch a ball rolling along a left-to-right track immediately after the ball appeared from the left side. The soccer play activity had the children freely kick handmade paper balls (the number of balls was half or a quarter of that of children) in a playroom for two minutes. We found that, for children in the 4-year-old class, correlation coefficients between the number of ball-touches and locomotor skills were significant. In contrast, for children in the 5-year-old class, we found no significant association between the number of ball-touches and locomotor skills ; however, correlation coefficients among the number of ball-touches and variables on the approach direction were statistically significant. Thus, from our data, we conclude that for playing with balls, locomotor skills are decisive for the 4-year-old class children, but the ability to make good decisions about the approach strategy supplants this for the 5-year-old class children.

In the descending limb, where the muscle length is longer than the natural length, isometric force decreases with increasing muscle length. This implies negative stiffness, and the system is theoretically unstable. In vivo, however, stable positional control is achieved. Few studies have explored position control in the descending limb. We herein report a new two-mode Hill-type muscle model created based on the results obtained from physiological experiments of isolated frog semitendinosus muscle. Next, based on the experimental results of the human extensor digitorum communis muscle operating in the descending limb, we show that there exists a motor unit in which the firing frequency is lower during static position control than during isometric force control. By comparing the physiological results of this motor unit with the behavior of the model, we constructed a stable static position control mechanism in the descending limb experimentally and theoretically.

Many of post-stroke individuals have lost their forefoot rocker function during gait. The purpose of this study was to develop and evaluate a device (ROSI : Reverse Omega Shoe Insert) which could assisted forefoot rocker function during single stance of the paretic limb. The ROSI used in this study has an inverted omega shape made of carbon plates, and its apex is placed proximal to the Metatarsal pharangial (MP) joint. Sixteen ROSI patterns were fabricated according to an orthogonal table array, and the optimum shapes and positions of the ROSI were determined based on measurements of a healthy subject wearing a mimic trans femoral prosthesis. To confirm the validity of this ROSI, gaits of 16 patients were measured by a three-dimensional motion analysis system under two conditions, with the ROSI and an ankle foot orthosis under two conditions of the ROSI ancle foot orthosis with and without the dorsiflexion resistance. Results showed that the center of pressure moved more forward in the condition with ROSI and an AFO with dorsiflexion resistance. It was also found that the center of pressure moved distally beyond the ROSI axis, which was located proximal to the MP joint in this condition. This meant that the ROSI and AFO with dorsiflexion resistance facilitated the heel rise in a single stance of the paretic limb during gait of post-stroke individuals.

Maintaining and improving the ability to walk is important for extending a healthy life span. However, it is not easy to improve gait by strength training and gait instruction alone. As a new method to achieve gait improvement, we have developed a shoe that guides the user to achieve a correct gait by applying appropriate dorsiflexion and plantarflexion of the ankle joint torque in accordance with gait timing. An analysis of the gait of younger subjects wearing these shoes showed an increase in the sole angle to floor and peak ankle joint plantar flexion moment. The immediate and residual effects of these shoes on the gait of elderly subjects were next examined. The immediate effects included an improved sole angle to floor and clearance, while the residual effects were observed to be an increase in both the peak sole angle during swing phase and stride. This study is a new finding, showing that gait-guiding shoes can still improve gait in healthy elderly subjects. This finding provides a new guideline for gait-assist devices and is expected to be applied to efforts to extend healthy life span.

To improve the attractiveness of wheelchair athletics itself by enhancing the athletic skills of wheelchair athletes, scientific analysis studies have been conducted. In this study, we report on the development of a system that can be used at actual training scenes by further improving the technology for measuring push power in detail. The sensor system has a 6-axis force sensor, an acceleration sensor, and an angular rate sensor. From the values of the 6-axis force sensor, the position of the center point of application of push pressure on the hand rim and the 3-axis force on the said point were calculated. To convert the calculated values into an absolute coordinate system, the rotation angle of the 6-axis force sensor in relation to the vertical direction was estimated from the acceleration sensor and angular rate sensor values. The estimated results were sectioned for each cycle, and the push power for each cycle was displayed in detail in graphs. Several athletes have already been measured using this system. It took about 60 minutes to prepare for the measurement. Trials lasting about 5 minutes were repeated a certain number of times, and then feedback was given to the athletes and coaches.

Children with intellectual disabilities require communication aids such as communication cards and/or voice-output communication aids (VOCA) to help develop their communication abilities in education. We developed an augmented-reality (AR) -based VOCA, referred to as VCAN/AR, to attract the attention of children with severe intellectual disabilities that have no interest in using conventional tools. The proposed VCAN/AR includes a computer, an LCD, a webcam, loudspeakers, and picture-card markers. When the user’s hand hides one of the picture-card markers, the VCAN/AR system plays a sound corresponding to the marker and simultaneously displays an animated 3DCG symbol overlaid on the marker on the display. We performed an experiment involving one student and three kindergarteners with intellectual disabilities to verify the effectiveness of VCAN/AR on the user’s motivation for accomplishing the given tasks for communication training. The experiment results indicate that the AR-based symbols of VCAN/AR function as rewards that allow the three subjects to accomplish the given tasks. Thus, VCAN/AR can be used to motivate certain types of subjects to perform specific tasks.

Flatfoot is a well-known foot deformity and is generally evaluated by clinical measurements (Foot Posture Index [FPI-6]) and radiographic measurements. However, these measurements have some limitations, such as a dependence on the examiner skill and versatility. We therefore examined whether or not foot shape indexes for assessing flatfoot are more useful than radiographic measurements. A total of 208 feet from 104 adult women with foot diseases were measured by a three-dimensional (3D) foot scanner to evaluate the radiographic appearance. The heel angle, leg heel angle, arch height ratio, medial arch angle, instep angle, medial protrusion area, heel center angle and curve angle were extracted from 3D foot scans and referenced against the FPI-6 to determine foot shape indexes. Foot shape indexes in the sagittal plane were found to have a strong correlation with the radiographic indexes (r=0.558～0.813, p<0.01). The medial arch angle was particularly notable, and a recipient operating characteristic analysis demonstrated that its area under the curve was 0.867 (p<0.01), and its cut-off value with 87.9% sensitivity and 76.7% specificity was 29.66. In addition, significant correlations were confirmed in the frontal and horizontal planes (r=0.216～0.625, p<0.01). These findings led to the conclusion that these eight foot shape indexes were useful scales for assessing flatfoot.

The aim of this study was to clarify the motions and mechanisms of changes in the posture of the kicking foot when kicking a launched ball toward different directions during soccer side-foot kicks. Ten male collegiate soccer players kicked the launched ball toward three targets 7 m away that were placed front of them with 30 degrees intervals. The pelvis showed different rotation through the ball impact between the target directions because the players turned their anterior pelvises toward the target direction. In contrast, there were no differences in the rotation of each joint of the kicking leg between the target directions. These results suggest that players kick the ball toward different directions by adjusting the posture of the pelvic rotation without largely changing the motion of each joint of the kicking leg.

The present study investigated and compared the catching technique of catchers with that of players at other baseball positions, including pitchers, infielders, and outfielders, through sensory evaluations and biomechanical analyses. Eight registered catchers were compared with eight registered players from other positions, where they caught a ball released from a machine at 130 km/h. The study found that sensory evaluations by the pitcher were higher in the catcher group than in the non-catcher group. Moreover, the sound of the catch suggested that the catcher group were able to catch the ball more accurately ; the distance travelled by the mitt after contact was significantly smaller for the catcher group. The mitt velocity suggested that moving the mitt to the left and upwards is crucial for successful catching. The study also revealed that catchers exhibited higher activity in the extensor carpi radialis muscle immediately before ball contact, which was inferred as a preparatory action for pulling up the mitt.

The purpose of this study was to examine the success or failure of the speed-accuracy trade-off relationship in badminton backhand drives and to clarify technical characteristics. The subjects were 10 male college badminton players. Backhand drives performed by the subjects at specified subjective-effort levels were recorded using a three-dimensional motion-capture system and surface electromyography (EMG) ; 500 hitting performances, 200 upper-limb-joint movements, and 180 electromyographic data were selected for analysis. Each drive was divided into takeback and swing phases, and the maximum and minimum values of joint angles, joint angular velocities, and %RMS were calculated and analyzed. With increasing subjective effort, the shuttle velocity increased but accuracy remained constant : there was no observed trade-off between them. Kinematic analysis suggested that the shuttle velocity was increased by increasing the angular velocity of the joints, while the accuracy was maintained by keeping the range of motion of the upper limbs constant as subjective effort increased. The flexor carpal ulnaris muscles may be performing tensile contraction during the take-back phase, as the EMG data showed an increase in its activity during the second half of it.

This study aims to propose a method for estimating the deformation tendency of the foot arch during long-distance running by analyzing the running form. Seventeen men who had regular running habits and experience in running 10 km participated in this study. The trial involved running 10 km on a treadmill with a reflective marker attached directly to the foot using processed shoes. The running motion every 1 km and the static standing posture before and after the 10 km running were measured using a motion capture system. Thus, the arch height at the timing of maximum deformation during the support phase of the running motion could be approximately estimated from the running form. However, the results also suggested that processing the shoes and attaching the reflective marker directly to the foot is necessary to determine the three-dimensional deformation tendency of the foot associated with the disability caused by the extension stress of the tibialis posterior muscle.

We developed and systematized a therapy for motor paralysis based on kinesthetic illusion by visual stimulation. Additionally, we provide evidence on the clinical efficacy of a Passively-induced Kinesthetic Illusion therapy (P-KI therapy) that does not require voluntary effort and can be applied to patients with the most severe upper limb motor paralyses after stroke. Some patients improve motor function after P-KI therapy, but may have difficulty transitioning to the next level of the treatment such as functional electrical stimulation. For this type of patients, we have also developed a Voluntary-controlled Kinesthetic Illusion therapy (V-KI therapy), which is a kinesthetic perception feedback therapy in which the patient plays with a virtual body driven by electromyography. In one patient with upper limb motor paralysis after stroke, V-KI therapy was applied, resulting in improved motor function.

We have continued to study methods for cognitive augmentation of motor function by kinesthetic perception using visual stimulation (kinesthetic illusion induced by visual stimulation : KINVIS), in order to apply it to the treatment of upper-limb motor paralysis that occurs after nerve injury such as stroke and spinal cord injury. In this article, we introduce our previous study that showed that the application of KINVIS for 20 min, which evokes kinesthetic perception, improved their ability to induce motor imagery in post-stroke patients with severe paralysis who were unable to extend their paretic fingers for a prolonged period of time. In addition, we consider the possibility that the improvement of the ability to induce motor imagery represents the potential of the improvement of motor function by repeating the combination approach of KINVIS therapy and conventional therapeutic exercise based on supplementary data.

The vibration-induced kinesthetic illusion has been studied in the fields of rehabilitation and virtual reality to induce the sense of movement in humans. Although the kinesthetic illusion induces an illusory sense of movement in a human, there is a problem in that the occurrence rate of the kinesthetic illusion varies from person to person. Hence, it is necessary to develop a method to increase the occurrence rate of the kinesthetic illusion. In this study, we increased the occurrence rate of the kinesthetic illusion by combining vibration and electrical stimulation. Vibration stimulation was applied to antagonist muscles to generate the kinesthetic illusion, and electrical stimulation was applied to agonist muscles to induce the isometric contraction of a muscle. To investigate the effect of the combined method of vibration and electrical stimulation, we conducted experiments under four conditions. The first condition involved the application of vibration stimulation only, whereas the second, third, and fourth conditions involved the application of vibration and low-, middle-, and high-voltage electrical stimulation. The experimental results were analyzed using statistical models. The statistical analysis suggests that the effect of electrical stimulation on the occurrence rate of the illusion was statistically significant.

This study examined the effect of the observer’s gender on the perception of aesthetic visual impressions due to the combination of body form and gait pattern. A two-way analysis of variance revealed no significant interactions, and significant main effects of gender and trial, respectively. Female observers demonstrated a greater degree of aesthetic evaluation than male observers. Post-hoc test results showed that normal gait in thin mannequins was more aesthetic than that in standard or obese mannequin, and that walk with an anterior tilted pelvis was more aesthetic than walk with a posterior tilted pelvis, regardless of the body form. Motion analysis revealed during walking with posterior pelvis tilted, greater hip flexion and knee flexion angles in the initial phase of stance than walking with anterior and normal pelvis tilted. Moreover, the upper and lower spine flexion angles were larger while walking with posterior tilted pelvis than while walking with normal tilted pelvis. It was suggested that changes in the movement of each body part in conjunction with the type of pelvic alignment may affect the aesthetic visual impression on observers.

In a variety of sports, visual functions in depth are important. Kinetic visual acuity and depth perception, which are existing methods for evaluating visual functions, have been used to reveal the property of visual functions in depth in athletes. However, since the existing methods do not directly reflect eye movements in depth, the property of vergence eye movements, which respond to visual stimuli in depth and are disconjunctive eye movements, in athletes is still uncertain. The existing methods and the ability of vergence eye movements could be independent of each other. Therefore, the purpose of this study was to reveal the differences between visual functions in baseball players and non-athletes using kinetic visual acuity, depth perception and vergence eye movements. The results showed that there was no difference in kinetic visual acuity and depth perception between baseball players and non-athletes. However, our results also showed that the latency and initial acceleration of vergence eye movements in baseball players were superior to those in non-athletes. Therefore, it is suggested that performance supported by the superior visual function in baseball players is associated with the properties of vergence eye movements.