The present study focused on freestyle swimming by swimmers with unilateral transradial deficiency. It has not been clarified yet whether the deficient limb should move so as to match the tempo of the intact upper limb, or if it should move as fast as possible to produce thrust by itself. The objective of this study was to solve the theoretically ideal deficient limb's strokes in freestyle for a swimmer with unilateral transradial deficiency by using the optimizing simulation. The method of the optimizing simulation of arm strokes considering muscle strength characteristics was developed in a previous study. This method was utilized to solve the deficient limbs' strokes in the present study. Actual swimming by a participant was reproduced by simulation first. Since the resultant swimming speed of the simulation was in the range of the experimental speed, the validity of the simulation was confirmed. Next, optimizing simulations were conducted for the case of maximum shoulder joint torque multiplied by 1.0, 0.85 and 0.72. From these results, a significant increase in the swimming speed was found for the optimized cases. It was also suggested that the contribution by the deficient limb to propulsion can be increased by up to 15% of the intact limb. The optimized stroke was found to have a later timing and faster motion than the original stroke. This motion was realized by the principle that more joint torque can be exhibited in adduction than in flexion when the joint angular velocity was high.

Keywords

Swimming, Optimization, Freestyle, Unilateral transradial deficiency, Physical disability, Sports engineering

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[Advance Publication] (Proper information for citation will be announced after formal publication)

Sports prosthesis for lower-extremity amputees has a mechanical structure similar to flat springs, and its elastic energy is expected to improve sports performance. However, it is quite challenging to represent the mechanical phenomena during the takeoff action with sports prosthesis because the contact point to the ground moves based on the direction and deformation of the prosthesis. The purpose of this study is to propose a parametric model of sports prosthesis based on the flat spring design formulas to represent the deformation and rolling contact with the ground with a reasonable computational cost. The shape of the prosthesis is modeled as serial elements, and it can easily be changed by using design parameters, such as the curvature and length of each element. The curvature of each element of the prosthesis is modified by the deflection angle of the flat spring model, and the contact point to the ground is calculated by considering the deformation and rolling contact. The spring properties obtained from the proposed model well agreed with the result of a finite element analysis. Moreover, simulation results revealed that the deformed shape of the prosthesis and the takeoff action in the long jump qualitatively agreed with the actual phenomena. As future research, the proposed model, coupled with the human body model, will be applied to a computer simulation system to optimize the shape of the prosthesis in order to improve sports performance.

Keywords

Human dynamics, Simulation, Rolling contact, Ground reaction force, Long jump

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[Advance Publication] (Proper information for citation will be announced after formal publication)

The rapid increase in the aging population of Japan is becoming a serious social concern, and the number of elderly individuals with dementia is also increasing. The Ministry of Health, Labour and Welfare of Japan has reported that the elderly account for 4.62 million individuals, of which approximately 4 million have mild cognitive impairment (MCI). However, monofunctional disorders, such as those in individuals with MCI, can be treated, with patients recovering 44% of their abilities 2 years after treatment, thereby suggesting that early detection and treatment of dementia is important. It has been reported that individuals who walk slowly or have experienced a significant decline in walking speed with age have a higher risk of developing dementia. In this study, to study movement in individuals aged ≥ 60 years, we focused on walking, a basic activity of daily living. We proposed and evaluated novel methods to estimate cognitive function. Acceleration and angular velocity sensors were attached to the waists of 20 elderly participants who were asked to walk outdoors ordinarily for 5-10 min, during which acceleration and angular velocity were measured. The similarity, standard deviation, and period of the stride were determined from the acceleration waveform and angular velocity waveform during walking. These were used as independent variables, and multiple regression analysis was performed using the Mini-Mental State Examination (MMSE) score as a dependent variable. An MMSE score estimation equation was constructed. The relationship between the estimation formula and the actual test value was R² = 0.773 (P <0.01), which was good. As a result of cross-validation, the root mean square (RMS) error is low and the error is neither fixed nor proportional. Using the body acceleration and angular velocity information when walking outdoors, we built a very accurate formula for estimating the MMSE score.

Keywords

Dementia, Walking, Elderly, Mild cognitive impairment (MCI), Motoric cognitive risk (MCR), Mini-Mental State Examination (MMSE)

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[Advance Publication] (Proper information for citation will be announced after formal publication)

Until now, numerous studies on the effects of electrical stimulation on nerve cell activation in a cell culture have been conducted. However, there are very few studies that have used the three-dimensional (3D) culture system to investigate nerve cell axonal extension. In this study, we developed a novel 3D direct current electric field (DCEF) stimulation bioreactor, which can uniformly stimulate cultured nerve cells for a long period. We observed the morphogenesis of PC12 cells using a multi photon excitation fluorescence microscope (MPM) and evaluated DCEF stimulation effects on PC12 cells axonal outgrowth. First, a DCEF stimulation bioreactor was designed using finite element analysis for uniform electric field. We, then, validated the uniform stimulation of PC12 cells using this bioreactor for 24 h. Second, we determined the optimal stimulation condition using the response surface method and adopting objective functions, such as axonal length, the ratio of axonal orientation towards the anode, and design parameters, such as the electric field strength and the duration of the stimulation. We found the optimal condition to be 43 mV/mm and 6.2 h/day for axonal length enhancement. An increase of 20.1% against the condition for the control group (Mann-Whitney's U test, p<0.05) was obtained. In addition, the 92 % of PC12 cells were oriented toward the anode with 90 mV/mm, 24 h/day condition. However, the axonal formation was suppressed depending on the stimulation duration. Finally, we found the optimal conditions of 70 mV/mm and 7.9 h/day for achieving the enhancement of axonal extension and orientation, simultaneously.

Keywords

DCEF stimulation, 3D culture, Bioreactor, Axonal outgrowth and orientation control, Optimized stimulation

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[Advance Publication] (Proper information for citation will be announced after formal publication)