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.
To evaluate the frictional heating effect during ski gliding by temperature measurement, a temperature measurement system was developed and evaluated numerically and experimentally. The portable temperature measurement system with high temperature resolution and accuracy consisted of thermistors and a portable logger with a 24-bit A–D convertor. The thermistors were inserted in a hole in the ski board with thermal conductive adhesive. By using numerical simulation, the difference between the interface temperature and the averaged temperature in the sensing region was evaluated. The temperature difference was proportional to the value of frictional heat generation, and the maximum difference in the experimental range in this study was 0.17 K. To test the developed system, a gliding experiment was conducted at Shinjo Cryospheric Environment Laboratory. Three thermistors were installed in the ski board, and a moving object was constructed on the ski. By pulling the moving object with a guide wire, the moving object was glided, and the interfacial temperature was recorded. In the case of a total weight of 54 kg, which was near the optimal weight, the thermistor installed near the heel position had a large increment of temperature. In addition, similar temperature increments were observed during the acceleration phase of the moving object. After the acceleration phase, the gradient of the temperature increment changed. It was inferred that the variation of gradient was affected by the variation of the force balance on the moving object. This suggests that the local contact condition and friction might be estimated through temperature measurement.
In this study, as part of efforts to assist beginners in sports such as tennis and badminton in selecting the most suitable equipment, an index for objectively evaluating such equipment is proposed. To accomplish this, standard swing trajectory variations are used to create an index from the viewpoint of human motion control. We begin by noting that human body data gained via motion capture are large in number because of the wide variety of equipment types used and due to the significant diversity of human body characteristics. Hence, even though motion capture devices are often used to capture swing motions, the most suitable human body segments for use in equipment evaluations have not yet been clarified. To facilitate this, it is necessary to reduce the overall number of body segments under consideration. In this paper, the method of deriving the feature points in sports motion was examined. More specifically, in order to obtain fundamental findings, tennis stroke and badminton smash motions are used as representative movements, and experiments using a motion capture device are performed. In the motion analysis that follows, we then investigate which markers can most clearly express the relationship between the racket and the human body in order to capture stroke motion characteristics. Then, an index of contribution is adapted to tennis swing and badminton smash motions, the motion feature points in the stroke and smash motion are derived, and the significant markers for motion analysis are identified and discussed.
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.