When participating in sports, athletes must display their motor and cognitive abilities simultaneously. The integration of these abilities influences their sports performance. Therefore, a dual task that combines a motor task with a cognitive task may allow us to observe the subtle differences in sports skills at the expert level. In this study, to estimate sports skills experimentally, we developed a real-world dual task comprising a motor task and cognitive task that athletes typically complete during competition. Soccer and baseball players who participate in university-level competitions were recruited for the experiment, and the difference between regular and semi-regular level players was investigated. The results indicate that in the dual task, the performance of the semi-regular group deteriorated but that of the regular group did not. Moreover, it is suggested that the factor that distinguished both groups was the difference in their cognitive abilities. We concluded that the dual task was successful in allowing us to observe the subtle differences in the sports skills of athletes who have the same level of fundamental motor skills. The findings of this study will be useful for managers or head coaches who need to select regular players.

In this study, we investigated the influence of kinematics and electromyographic variability on a ball-bouncing task under different speed conditions. Expert and novice subjects carried out ball-bouncing tasks at three speed conditions, and we examined the differences between expert and novice subjects’ bouncing movements in terms of the amplitude of the angular displacement of the upper limb and the muscle activity. Subjects were instructed to synchronize their ball-bouncing movements with three speeds (Slow, Prefer, Fast) via an external audio signal. The angular variations of the three joint angles of the upper limb and electromyograms (EMGs) were recorded, and the cocontraction index (CI) of agonist and antagonist muscle activity for each joint was calculated. The amplitude of angular displacement and the EMG of each muscle were varied by increasing the bouncing speed, which mainly increased the activity of the elbow and wrist muscles. The CI for an expert’s wrist in the fast-speed condition was less than that of a novice. Moreover, the relationship between elbow angle and the corresponding CI of the elbow was different for an expert and a novice subject. The results of this study indicate that experts bounce a ball with less joint stiffness and perform more efficiently in fast-speed conditions.

This paper deals with two gymnastic maneuvers on the high bar, the kip movement and the giant swing backward movement, as a task under a second-order nonholonomic constraint. Since the movements in such a system are highly restricted by the constraint, imagining to what extent redundancy exists between an initial and a final configuration that defines the task is difficult. Thus, we study the redundancy underlying high bar movement tasks by constructing a simple dynamical model of the high bar movement. The time histories of the angles of the actuated joints are parameterized by a spline function or a Fourier series, whose movements are confirmed to be approximately consistent with the measured movement of an expert gymnast.Using this model, we propose a systematic method to calculate a set of spline/Fourier parameters that achieves a task. The redundancy part underlying the kip and giant swing backward movements is concretely illustrated. Moreover, we discuss the possible optimization criteria that explain the high bar movements of the expert gymnast using the calculated parameter set.

We investigated the effects of long-term motor practice on peripheral and central nervous systems (CNS) by measuring motor nerve conduction velocity (MCV), as well as by measuring movement-related cortical potentials (MRCP) associated with self-paced right (dominant) and left (non-dominant) brisk handgrip movements with a 20% maximal voluntary contraction via electrodes placed on the scalp of elite kendo players and healthy young adults (control). In experiment 1, MCV was measured from the ulnar nerve in the forearm of all subjects. The MCV of both dominant and non-dominant limbs in athletes were significantly faster than those in controls. In experiment 2, three components (Bereitschaftspotential: BP, negative slope: NS’, and motor potential: MP) of MRCP were obtained from all subjects. The BP latency for the non-dominant handgrip task was significantly longer in the controls than in the kendo players. BP onset time appeared significantly earlier preceding the non-dominant handgrip task as compared with the dominant handgrip task only in the controls. Moreover, MP amplitudes in the kendo players were significantly larger than those in the controls. These findings suggest that long-term motor practice induces practice dependent changes in kendo players’ brain activities, especially in the non-dominant hand movement, compared to that in the dominant hand. In conclusion, long-term motor practice may exert adaptive changes not only on the peripheral nervous system but also on the CNS in humans.

For the quantitative evaluation of soccer skills, a camera system that allows 3-D motion analysis has been used to date. In the quantitative analysis of kick motions, the movements of lower extremities are evaluated. In order to understand the kick motion in detail, it is necessary to evaluate not only the movements of the lower extremities but also those of the lumbar region. The aim of this study is to evaluate the difference in the movements of the lumbar region with respect to the instep kick motion between skilled players and beginners. The measurements of kick motion were obtained using a state-of-the-art motion capture system. The comparison revealed that the movements of the lumbar region play a role in the sharp movement of the thorax, transfer of energy from the lumbar region to the lower extremities, and posture stability.

Most of women are interested in not only their bodies but also their walking postures. In this study, we developed a pantyhose to improve the gait motion focusing on the toe-out-gait. We measured deformation of the hip and thigh surface, and found the areas that were and were not extended by hip and knee flexions during walking. Therefore, we proposed placing elastic belts spirally around the legs to generate internal-rotation forces only during walking. To evaluate the proposed pantyhose, we tested it on five toe-out-gait female subjects. Wearing the pantyhose, improved the walking postures of all the subjects. In addition, the pantyhose did no increase knee abductions nor prevent the subjects taking a seating position.

Pumps, one of the most popular types of ladies’ shoes, have a good appearance. However, they sometimes slip off from the heel in walking due to their short insteps. In this study, we attempted to mitigate the slippage of pumps by applying dynamic foot deformation to make them fit better during walking. From the results of gait analyses, we found that the slippage occurred before heel-off. In this period, because the plantar arch is extended, the navicular bone is bulged and the length around the ball-jointed girth is stretched. Therefore, we propose a mechanism for decreasing the slippage using a stiff line, which can fasten the topline of the pumps by applying the stretch of the ball-jointed girth. We tested this by arranging a line between the inner and outer leathers of the pumps, starting from the ball-jointed girth to the topline like a figure-of-α. Using a prototype with of line mechanism, we measured the slippage for 10 feet of 9 female subjects. As a result, for all subjects, the slippage significantly decreased approximately 23% at 50% of the gait cycle. Furthermore we confirmed endurance of the effect after daily use.

We have tried to develop a mouthpiece type remote controller for severely disabled people such as those with cervical cord injuries and/or muscular dystrophies. This remote controller would be inserted into the user’s mouth and be operated by tongue movement. Tongue movement is one of the voluntary functions that usually retains its function, even in the case of cervical cord injury. The specification of the mouthpiece type remote controller is explained. The performance and operativeness are evaluated in this paper.

 We developed a 4 channel remote controller to operate a powered wheelchair; forward, right, left and backward. This controller has four passive RFID (Radio Frequency IDentification) transponders. Each transponder generates electric power by itself, so it can work without a battery. The MCR (Maximum Communication Range [mm]) was evaluated in three conditions of atmosphere, water and meat. The MCR was 110 mm or more in every condition. In the case of the remote controller being inserted into the participant’s mouth, the performance of the MCR satisfies the design specification. With this system, we succeeded in operating an electric powered wheelchair on the market.

Using an electric powered wheelchair for children with severe disabilities at an early stage has been described as beneficial for developing their mobility. However, their scope of potential is limited compared with healthy children because when they move using a powered wheelchair, their line of sight is lower, their arms are required for the operation and their body never masters the ability to balance. The purpose of this study is to develop a powered wheelchair for children with severe disabilities to encourage their development. A new powered wheelchair with a body sensation equal to “two-legged locomotion” was thus produced. The developed prototype function is equipped with “A half standing positioning mechanism,” “An operation system with lower limbs” and “A swaying seat function.” The basic system function was evaluated by a healthy participant, while the required functions were evaluated by a participant child. Consequently, it was confirmed that a line of sight equivalent in height to that of a healthy child was achieved by the half standing position mechanism, the drive of the wheelchair and the workspace expansion of the upper arm by the lower limb operation system and the activation of muscle activity by the swaying seat. Accordingly, it was suggested that the powered wheelchair developed showed the potential to encourage child development.

In this paper, we describe a passive power assist system for the lower limb rehabilitation. The proposed system is composed of a mechanical gravity compensation system and a mechanical stiffness control system. By employing the clutch mechanisms, the proposed mechanical stiffness control system can present the desired stiffness around the tip of the system for arbitral postures. On the other hand, the gravity compensation system in the proposed system can produce the large gravity compensation force by amplifying the restoring force of the spring by a gear with high gear ratio. The system is safer than the previous ones because the total system is embedded within the link bodies. Thus, it will be preferable for wearable rehabilitation systems. The good performance of the proposed system as a gravity compensation system and a linear stiffness presentation system were verified through some experiments.

Tactile sense is the third most important sense after visual sense and hearing sense. Recently, cognitive psychology studies on tactile illusions have gained attention because of the potential applications of such sensations in tactile displays and interfaces. In this study, we focused on a unique and interesting sensation called “velvet tactile illusion,” and we examined the possibility of creating this illusion by passive touch. We investigated the relationship between some factors related to the creation of this illusion and the percentage of creating the illusion by passive touch. We then developed a device to evaluate the creation of this illusion by passive touch. This device can control factors such as line movement velocity, line diameter, and line distance that influence the creation of the velvet tactile illusion. Using this device, we conducted exhaustive tests for different values of these factors. In addition, we conducted an experiment to examine the influence of some factors on the creation of velvet tactile illusion by passive touch. The relationship between some factors related to the creation of this illusion and condition of creating the illusion was found. These data will be helpful data when we develop the new tactile display regarding velvet tactile illusion.

This paper describes decision processes of the system concept of an electric diary for promoting self-enhancement of persons with mild dementia. These persons need to be supported with their psychological situation, for example; anxiety stemming from their memory loss, depression from their cognitive impairment or other causes. Development of assistive products to directly support the psychological situation has been very difficult. In this project, we propose guidelines for the development of the kind of assistive products that have four features. 1) Psychological intervention model of the products, 2) Psychological confirmation of main functions of the products, 3) Psychological efficacy of the main functions of the products, 4) System concept of the products. The concept of the electric diary system was proposed according to these guidelines. It can select the contents related to the experiences promoting self-enhancement from all of the contents that the user has recorded, and then show them to the user. The investigation with 98 Japanese adults showed that these experiences categorize into achievement experiences and inter-personal experiences. And the experiment with a person with front-temporal dementia suggested the psychological efficacy of this system. This decision process supported the effectiveness of the proposed guidelines for development of the assistive products supporting the psychological situation of persons with mild dementia.

Due to the importance of understanding the scientific basis in the succession of handwork skills, this study aims to clarify human factors contributing to the basis of handwork skills by examining glass grinding work. The glass grinding load manually added by workers was measured with a handmade force sensor. Four workers participated in this experiment : one novice, one intermediate, and two skilled workers. Two important force parameters, the intensity of load (IL) and the center of load (CL), were analyzed. With respect to IL, the novice worker maintained a high load level with weak intensity changes, whereas the skilled workers used a clear force rhythm with large intensity changes. Because the novice maintained a high load (vertical pushing force), he had to apply a strong muscle force against the grinding force (horizontal resistance force). Therefore, the novice’s method was tiresome. In addition, the results indicate that the CL patterns did not converge into a single mode among workers. However, based on a simulation, the CL patterns for intermediate and skilled workers were less influenced by force fluctuations compared to that of the novice. The results demonstrate that handwork skill compensates for human weakness; that is, handwork skill reduces fatigue and compensates for force instability.

In order to deeply understand the human jaw-movement mechanism, we have been developing an autonomous jaw-movement simulator, JSN, with a life-like design in anatomical structure as well as in control scheme. In this study, we equipped JSN/3A with the following three functions: 1) periodontal masseteric reflex, 2) detection of food elasticity and 3) feedforward control advancing the onset of masseter and internal-pterygoid activities after food detection, all of which are believed to be effective for efficient mastication. Simulation results suggested that the initial inhibitory phase of periodontal masseteric reflex has a role of reducing a sharp rise of the bite force immediately after tooth contact, whereas the following excitatory phase has a role of increasing the bite force. Food stiffness could be estimated by using two different sensory data of the wire length of the anterior temporalis actuator and the bite force applied to the upper first molar. The feedforward control was efficient to simulate a natural and effective bite driven primarily by masseter and internal pterygoid muscles.

Finger Braille is one of the communication methods utilized by deafblind individuals. In one-handed Finger Braille, a sender dots the left part of the Braille code on the distal interphalangeal (DIP) joints of the index, middle and ring fingers of a receiver, and subsequently dots the right part of the Braille code on the proximal interphalangeal (PIP) joints of the same fingers. Since there is a limited number of non-disabled people who are skilled in Finger Braille, deafblind individuals communicate only through interpreters. To assist communication between deafblind individuals and non-disabled people, we have developed a Finger Braille recognition system. In the present study, we analyzed the shock accelerations from the dotting of one-handed Finger Braille. The receiver wore small piezoelectric accelerometers on the bases of the index, middle and ring fingers. Each accelerometer measured the acceleration attributed to the dotting of the sensor-mounted finger (self dotting) and the acceleration from the dotting of the other fingers (cross talk). We analyzed the shock accelerations from self dotting and cross talk and then derived an algorithm for the recognition of dotted fingers. The estimated recognition accuracy of dotted fingers was 92.9%, when the sender and the receiver sat side by side. We also derived an algorithm for the recognition of the dotted position (DIP and PIP joints). The estimated recognition accuracy for the dotted positions was 81.9% in the identical seating position.

The purpose of this study was to develop a musculoskeletal model considering both central and peripheral muscle fatigues in order to evaluate the muscle fatigue during body motions quantitatively and circumstantially. Considering mechanical properties from motor intention to generation of the muscle force, a single muscle model including central and peripheral fatigue properties was first formulated from a computational point of view. The central and peripheral fatigue models were characterized by dynamics with a combination of fatigue and recovery, and the peripheral model was also influenced by the activation level of the muscle. A musculoskeletal model with the muscle fatigue models was constructed after considering the parameters identification method and optimization method with a cost function minimizing the muscle fatigue. The proposed fatigue model was compared with the experimental results from the previous studies. In order to evaluate the musculoskeletal model, pedaling motions on a bicycle ergometer were measured, and the computed muscle forces were compared with those from the previous model. It was found that the proposed model was more accurate than the previous model.

Many simulation studies of human gait have been conducted in the field of biomechanics. The theoretical methods in robotics have been applied for the motor control mechanisms with the musculo-skeletel model. An essential difference between the two-joint link systems in human extremities and conventional robots is the existence of the muscle coordination system with the three pairs of antagonistic muscles. These three pairs of antagonistic muscles in human extremities consist of one antagonistic pair of bi-articular muscles and two antagonistic pairs of mono-articular muscles. The existence of a muscle coordinate system contributes to force and compliance control at the end point, and the three pairs of antagonistic muscles show muscular coordination control patterns during limb push and pull isometric movements. This study describes the gait form based on the muscular coordination control pattern with the muscle coordinate system in terms of robotics simulation and electromyographic kinesiology. The results obtained herein demonstrate that the muscular coordination control pattern contributes to controlling dynamic trajectory at the endpoint, and that activities of only three muscles with a submaximal muscular coordination control pattern achieved a human-like gait.

The fusion index (FI) measured by muscle force is an index that can evaluate the tetanic progression of the skeletal muscles. The relationship between the FI and stimulation frequency is named a Fusion index - Frequency Curve (FFC). The FFC is expressed by the sigmoid function composed of two parameters (k and h). However, there are no reports of the FFC-equation applied by displacement MMG. In this study, FFCs of displacement MMG in gastrocnemius, vastus intermedius and soleus muscles of rats were measured, and FFC-equation was applied. As a result, the FFC waveforms of the displacement MMG resembled those of muscle force. FFC-equation can be applied to FFC of displacement MMG. The k parameter was affected by fiber compositions. In addition, k and h parameters can be easily estimated by the twitch. The k parameter of the displacement MMG may evaluate the change of fiber compositions caused by the muscle training, aging, disuse of muscle, and rehabilitation therapy.

The present study investigated the muscle activity characteristics of scapular muscles, mainly the rhomboid muscle, during shoulder movement. The study population comprised 6 male college students with no history of shoulder injury. We recorded the EMG of some scapular muscles during shoulder abduction : the rhomboid major and minor muscles were tested using a wire electrode; the serratus anterior and the middle trapezius, by a surface electorode. It was found that with the increase in the shoulder angle and load, the muscle activity of each scapular muscle increased significantly. In particular, the muscle activity differed between rhomboid minor and major muscles, and it was believed that the muscle activity of the rhomboid minor and serratus anterior increased with load. Therefore, it was thought that the rhomboid minor and serratus anterior muscles show load dependence, and the possibility that the coordinated movement between the muscles plays a role in the maintenance of the scaplothoratic joint during shoulder abduction was suggested.

Recently, so-called “core training” which focuses on muscles in the body trunk has attracted much attention. When discussing the stability of the body trunk, both Local muscles and Global muscles should be considered, but the importance of Local muscles has been studied more. Instructing a person verbally to halt urination is thought to prompt contraction of the transversus abdominis, one of the Local muscles. However, there has been no research that shows if this method is appropriate to prompt contraction of the transversus abdominis or what position is most effective. The purpose of this study was to investigate the appropriateness of this method and to determine what position is most effective to induce contraction. The participants were 61 male students (average age 18.1±1.8). They were instructed to halt urination in both supine and standing positions, and the thickness of the transversus abdominis were measured using an ultrasonograph. The thickness of those muscles at rest in both positions was also measured. The results showed that instructing a person to halt urination in order to prompt contraction of deep muscles in the body trunk was in fact effective to voluntary contraction of the transversus abdominis and adliquus internus abdominis, and the supine position was more effective. The result also showed that the standing position is effective to induce contraction of the transversus abdominis if it cannot be achieved voluntarily because when standing these muscles contract unconsciously.

The present study aimed to introduce a new index of muscle cross-sectional area (CSA) and to examine the relationship between the muscle CSA index determined during isometric maximal voluntary contraction (MVC) and muscle strength. As a result of the quantification of cross-sections of elbow flexor muscles at rest and during a low-intensity contraction using magnetic resonance imaging (MRI), the product of muscle thickness and circumference of a limb (MT×C) was shown to be appropriate to assess muscle CSA. In young adults, MT×C during MVC is similarly or more closely related to muscle strength than that at rest. On the other hand, in middle-aged and elderly individuals, MT×C during MVC is more closely related to muscle strength than that at rest. Thus, the age-related difference in the relationship between MT×C and muscle strength was found. Muscle deformation induced by MVC for middle-aged and elderly men is suggested to be greater than that for young men, and it would have affected the above age-related discrepancy. The present findings indicate that MT×C during isometric MVC is able to more accurately examine one’s ability to exert force than that at rest.