In this aging society, the importance of extending healthy life further increases. One of the measures and policies is the evaluation of walking ability based on gait kinematics. The purpose of this study is to obtain useful findings for the evaluation of walking ability in elderly people. 20 observers watched 103 whole body gait motions measured by Kinect v2 and performed subjective assessments on the motions. Influences of individual attributes or subjective assessments on the whole body gait kinematics were discussed. 7 anti-aging factors for apparent age based on the walking posture were selected. Those were faster walking speed, straight back, greater pelvic rotation in transverse plane, smaller toe-out angle, smaller mediolateral difference of knee direction, and smaller head sways in both anterior-posterior and mediolateral directions. Walking speed was an especially important factor for walking ability in not only physical capacity but also physical appearance. The importance of spinal alignment and lower extremity positioning was also discussed. Furthermore, it was suggested that specific factors for apparent age were associated to female-specific motions such as stable head and greater pelvic rotation. These findings could expand possibilities of the evaluation of walking ability applied to health promotion.

Although the motion of the shoulder joint should be analyzed in the motion analysis of the upper extremity, its detailed analysis is quite difficult, because the shoulder is a compound joint. Particularly, the motion of the scapula, which slides on the thorax, cannot easily be measured by using skin markers secured on the characteristic points on the scapula. To solve this problem, we developed a neural network-based method capable of estimating the scapular orientation from the 3D position of the skin markers measured by means of a motion capture system. As training data given to the network, we used the scapular orientation computed by a 2D/3D registration using a 3D model of subject’s scapula reconstructed from CT images and its fluoroscopic image as well as the 3D position of the skin markers measured simultaneously. Accuracy verification experiments employing 5 healthy volunteers demonstrated that the scapular orientation in a lateral elevation of the upper arm can be estimated in an accuracy of less than 3.0 deg in term of average RMS error.

The ability of rapid force development is one of the important factors for improving the physical performance. It has been known that rapid isometric force is controlled by a central motor program to keep the rise time relatively constant independent of force amplitude (pulse height control). The advantage of using pulse height control is to increase rate of force with force amplitude. However, this strategy is thought to be applicable up to about 50-60% of MVC. When the force level increases further, subjects often switch to pulse width control to increase the time to peak force. The purpose of this study was to determine the force level (turning point) at which subjects switch from pulse height control to pulse width control. This turning point was defined as the maximum force produced by pulse height control. We then attempted to examine whether this turning point is different among subjects. Our results showed that a turning point (%MVC) between two strategies was detected in all subjects and the mean values were significantly higher in the sprinter group than that in the control group. Our results suggest that each subject has different limits of force level produced by pulse height control.

In order to elucidate the function of the biarticular muscle described by Lombard’s paradox, the lever arm lengths of the long head of the biceps femoris and the gastrocnemius of a cadaver were investigated. The lever arm length of the long head of the biceps femoris was larger on the hip side than on the knee side even when the angle at the hip and knee joint changed, and became larger as the bending angle of the hip joint increased. The lever arm length of the gastrocnemius was larger on the foot side than on the knee side even when the knee and ankle joint angles changed, and increased as the plantar flexion angle increased. We designed a scaled wooden leg model based on the lower limb bone shape extracted from the cadaver, and attached rubbers imitating the long head of the biceps femoris and gastrocnemius in order to establish whether leg extension occurs. The biceps femoris long head rubber and gastrocnemius rubber both caused leg extension. The knee extension angular velocity of the gastrocnemius rubber was faster. These results suggest that the long head of the biceps femoris and gastrocnemius muscles act on leg extension in the standing position when the feet are fixed. The knee extension action of the gastrocnemius muscle is presumed to be strong based on data obtained on knee joint angular velocity from the wooden leg model.

We have previously reported the cerebral network activation and acute clinical effects of illusion on motor function during kinesthetic illusion induced by visual stimulation (KiNvis). This paper reviews a series of studies that investigated electroencephalographic (EEG) oscillations during KiNvis, as basic knowledge for applying the brain-machine interface using KiNvis in rehabilitation. In the left parietal lobe, the EEG oscillations during KiNvis differed from motor observation in that the EEG decrement in KiNvis showed area dependence. Therefore, the findings of this study suggest that the part that corresponded to the left superior parietal lobe may be an appropriate region for distinction of the difference of EEG oscillation between KiNvis and motor observation. We speculate that this knowledge will prove useful for the development of algorithms that can confirm the intensity of kinesthetic illusion in clinical rehabilitation.

This study aimed to clarify the effect of repetitive rotator cuff exercise on corticospinal tract excitability, which concerning the control of the external rotator muscles during shoulder joint abduction. We examined the corticospinal tract excitability before and after the rotator cuff exercise by using transcranial magnetic stimulation (TMS). The exercise was repeated 100 times every 15 minutes for total of 300 repetitions. The corticospinal tract excitability during shoulder joint abduction was measured by using motor-evoked potentials (MEPs). TMS was applied to induce MEPs in the infraspinatus, middle deltoid, posterior deltoid, and lower trapezius muscles during the isometric shoulder joint abduction. Abduction was performed 20° in the scapular plane. MEPs were measured twice before exercise (pre1, pre2), immediately after each exercise (exercise1, exercise2, exercise3), further, and 30 minutes and 60 minutes after the third exercise ended (post30, post60). The MEP amplitude of the infraspinatus muscle was significantly increased until 60 minutes after the exercise ended in comparison with that measured at pre1, whereas there was no significant difference in the MEP amplitudes of the other muscles. The present study demonstrated that the corticospinal tract excitability of the infraspinatus muscle was increased during shoulder joint abduction after the intervention exercise.

This study investigated the effects of individual differences in the weight of somatosensory inputs from lower extremities on balance control movement while standing on an unstable board. The weight of somatosensory inputs was estimated based on participants’ sensitivity to the perturbation induced by a compliant surface. The unstable board had a narrow support surface width of fifteen mm and was unstable in pitch or roll plane depending on the direction of its support surface setting. Participants were instructed to stand upright on the unstable board as motionlessly as possible for 315 seconds. Coherence analyses were conducted on between kinematics data of participants’ lower and upper body. The results revealed that, in both cases of unstable in pitch and roll plane, participants who put more weight on lower limb somatosensory cues tended to coupled their lower and upper body motions more strongly for balance control.

Many patients with cerebrovascular diseases and the elderly have difficulty ingesting foods because of dysphagia. We hypothesized that repetitive contraction of the suprahyoid muscles via peripheral nerve magnetic stimulation could lead to recovery of swallowing function. The magnetic stimulation coils currently on the market are problematic because not all tissues around the suprahyoid muscles should be affected during magnetic stimulation, such as the alveolar nerve. The problem is due to the wide area covered by magnetic stimulation. With this factor in mind, we designed and fabricated a coil optimized to provide only a narrow range of stimulation. By adopting use of a magnetic core, we ensured that the coil distributes only a local eddy current during stimulation. We confirmed that the magnetic stimulation using this prototype coil could cause large contractions of the suprahyoid muscles without stimulating the alveolar nerve.

Powered prosthetic arm is a necessary device for person with bilateral shoulders disarticulation cause by accident or illness. In recent years, persons with bilateral shoulder disarticulation are challenging to operate multiple Degrees-of-Freedom (DOF) electrically powered artificial arm. However, the multiple DOF electrically powered artificial arms which are tested for practical use has unresolved contradicting fundamental problems on mechanism, DOF, and control. In this research, we propose and are developing hydraulic-electric type powered artificial arms. A wearable-type 5-DOF unit taking advantage of the remaining function of the upper extremity motion and a desktop non-wearable unit with 2-DOF external terminal are composed. Hydraulic Bilateral Servo Actuator, which combines the controllability of electric control and the high output of hydraulic system, are implemented in the powered artificial arm. The system significantly changes the previous design concepts of artificial upper limb by features of 1) highly rigid joint mechanism without using a gear reducer mechanism, 2) a bi-articular muscular hydraulic cylinder actuator that functions as upper arm frame structure and simultaneously and independently drives the shoulder and elbow, and 3) a forearm with rotary-type hydraulic actuators consisting a 3-DOF highly rigid joint mechanism. In addition, each digit on the 5-DOF hand is driven by a electric motor for precise positioning and the variable arch structure palm is capable of adjusting to grasping object shapes by its passive rigidness adapting function.

This research aimed to verify the influence of the function of the ankle joint of prosthetic foot on steady state gait. The index used was the mechanical energy conversion efficiency value. Gait analysis of normal subjects with simulated trans-tibial prosthesis was performed using a three-dimensional motion analysis system. A single-axis prosthetic foot was used, as it allowed for plantar flexion and dorsiflexion of the joint. The mechanical energy conversion efficiency value was calculated using COG data obtained by the system. The conditions of ankle function were compared between the first and the second phase of the stance. As a result, the rising phase, which is the first half of the stance, was greatly affected by dorsiflexion. Walking efficiency improved with increased restriction of dorsiflexion. The second phase, the descent phase, was affected by dorsiflexion and plantar flexion. However, ankle joint fixation produced the best result. In addition, a comparison of Solid Ankle Cushioned Heel (SACH) foot and energy storage and return prosthetic foot resulted in the SACH foot showing closer to normal gait. In conclusion, in the case of prosthetic walking and steady-state gait, abolishing the ankle dorsiflexion function has been suggested.

This study deals with an above-knee prosthesis that allows amputees the ability to ascend and descend stairs with no external energy supply. Our previous study certified that our hydraulic system, which is propelled by antagonistic actions of the knee and ankle joints, enables an individual to ascend and descend stairs as well as walk on flat surfaces. However, the device requires an operations manual of the flow control valve (FCV) of the hydraulic system prior to ascending stairs in order to interlock the knee joint and the ankle joint. Moreover, it has obstacles which deteriorate the walking gait, such as being unable to reproduce a double knee action. This paper discusses a solution for these difficulties as well as subsequent developments to provide amputee a walking gait which is liken to a normal one. We combined a new flow control valve (FCV) into the hydraulic system which is automatically driven while the individual is walking. The walking experiments certified that the new mechanism provides a double knee action that normally appears in healthier persons’ walking gaits, and it also provides a smooth transition from level walking to ascending stairs. However, instabilities were discovered when descending stairs.

This study aimed to analyze the effect of heel lift pads in ankle-foot orthoses on dynamic motion aspects of gait in stroke patients with limited dorsiflexion from the viewpoint of energy conversion efficiency. Fourteen chronic stroke patients who were ambulatory and had lower extremity motor function categorized as Brunnstrom stage Ⅳ participated in the study. A three-dimensional motion analysis system was used to assess the effect of the heel lift pad intervention on dynamic motion gait parameters. This study was a single-system A-B-A design. It was demonstrated that energy conversion efficiency and walking speed increased with the heel lift pad (P<.05). We also conducted a single case study as an external validity test and revealed that the orthosis with the heel lift pad significantly improved the rocker function of the foot-ankle system.

Recently, principal component analysis (PCA) has attracted increasing interest in biomechanical studies because of its usefulness in identifying the movement characteristics of various groups under various conditions using whole data waveforms. However, previous studies using PCA on the matrix constructed from the data of whole trials failed to separate the inter-subject component and the intra-subject component of gait features in their analysis. Therefore, this study proposed a new method to clear this problem and verified its relevance by comparing the gait features of fallers and non-fallers between the proposed method and the ordinary method. As a result of this study, we found that (1) both methods output similar gait features, but (2) the repeatability of proposed method was much higher than the ordinary method.

Proximal femur fractures due to osteoporosis are one of the serious health issues in aging societies. Osteosynthesis employing pin-or screw-type implants is widely used for femoral neck fracture treatment in Japan. Unfortunately, complications such as secondary fractures may occur during the postoperative rehabilitation period. In order to reveal the potential cause of the postoperative fracture from the viewpoint of biomechanics, this study explores and proposes a novel dynamic stress analysis of the treated proximal femur based on finite element (FE) analysis via ABAQUS. A new subject-specific 3D left hip joint FE model was constructed from the CT images of an elderly female volunteer. The model consists of the pelvis, proximal femur, cartilage, and Dual SC Screw (DSCS). Dynamic loading and boundary conditions were applied to the model for simulating gait motion. The time-dependent loading forces acting around the hip joint were obtained by the inverse dynamic analysis of human gait using an in-house lower-limb musculoskeletal model. These loading and boundary conditions for simulating the gait motion are the major technical advantages of the proposed dynamic FE analysis over the conventional static FE analysis. The simulation results successfully demonstrated the detailed time-dependent stress distribution and excessive local stress concentration for the DSCS treatment ; the excessive local stress concentration is the potential cause of subtrochanteric fractures during the postoperative rehabilitation period. The proposed dynamic FE analysis has proved effective in assessing the postoperative fracture risk of osteosynthesis with implants.

The purpose of this study was to propose a simplified foot stiffness evaluation method, and to clarify the influence of the foot stiffness on loading rate at heel contact in the practical running. Thirteen male heel contact strikers participated in this study, and the navicular height and vertical ground reaction force in the seated and standing conditions by using of a motion capture system and a force plate, respectively. Foot Stiffness is calculated as vertical ground reaction force change divided by change of navicular height ratio from seated to standing condition, and Simplified Foot Stiffness is calculated as 38.575 percent body weight, which is calculated as subtracting 11.7% body weight (determinated by segment mass of foot, shank and thigh and mass center position of thigh) form 50% body weight (standing condition), divided by change of navicular height ratio. In addition, maximum loading rate of each subject was measured in the practical running in the speed of 3.3 m/s by use of a force plate. The results are as follows : (1) Simplified Foot Stiffness corresponded to Foot Stiffness and (2) there is significant positive correlation between Simplified Foot Stiffness and maximum loading rate (r=0.889, p<0.01). These results indicate that loading rate in practical running can be predicted by evaluation of change of navicular height without vertical force measurement.

The purpose of this study was to clarify the characteristics of the change in the medial longitudinal arch height occurring inside the shoe during long distance running. The subjects were seven male college students who had experience of running 10 km distance and running habits. Specially modified shoes and socks were worn by the subjects so that reflective markers could be affixed directly to the feet. The trial was done in order of (1) static standing posture, (2) 15 m running on the flat road, (3) 10 km running on the treadmill, (4) 15 m running on the flat road, and (5) static standing posture. The results were summarized as follows : 1) In the static standing posture after long-distance running, the arch height ratio decreased. 2) The medial longitudinal arch during running was gradually deformed. 3) Comparing the arch height at the 0 km point and the 10 km point, the minimum value of the arch height ratio increased in some subjects. 4) Factors that caused the minimum value of the arch height ratio to change were the forefoot segment angle, the lower leg segment angle, and the position of the foot center of gravity relative to the center of gravity.

We aimed to determine the effects of a handrail on reaching distance, moving speed, acceleration, and the time to reach maximum speed during an attack in wheelchair fencing. We enrolled five healthy students and observed their attacks under three conditions : no railing, low railing, and high railing. The performance was photographed and analyzed using a three-dimensional motion analysis device. There was no significant difference in the maximum distance traveled during an attack under the three conditions. Speed and acceleration were significantly faster with the railing. Similarly, the time to reach maximum speed was significantly shorter with the railing. The difference in heights of the handrail did not affect the performance in any item. The handrail increased the speed and shortened the time to reach maximum speed. The handrail is important in wheelchair fencing, which requires quick movements and turnovers with attacks and defenses.