Comfortable condition of individual sitting was measured with a newly developed experimental chair and the reasons of differences in the individual conditions were analyzed. The chair system is able to adjust freely in the size, angle, cushion, and surface curve. Backrest and seat are divided into 10 and 6 units respectively. Normal and shear forces acted on supporting plate in each unit, and its sinking depth were easily measured, while sitting. The backrest block and the seat block can be inclined independently with hydraulic jacks attached on both sides of the chair. The height of seat is adjusted relatively with the elevation of floor level on which a force plate is mounted. There is no difference in sitting feeling that is confirmed by alternative sitting test. As an example, comfortable distribution of cushion in automobile back-seat was analyzed. The results show that the taste on the distribution of cushion hardness correlates with the individual flexibility of hip and lumbar flexion, and the suitable and permissive distribution of backrest cushion is the partial hard type supported at hip and lumbar parts.

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This study examines the effects of visual feedback's discreteness on fine positioning tasks. An experiment is performed in which computer's mouse is positioned under human's eye-hand coordination. In the experiment the following three factors were examined; a form of visual feedback, i.e. analog and digital, a Control/Display ratio and a cycle time of visual feedback. Results are summarized as follows. Movement Time (MT) becomes larger for the digital feedback and with the cycle time because of the discreteness of the visual feedback. In case that the cycle time is smaller than 240msec, however, no improvement of the performance is observed, because human's reaction can't catch up with the feedback cycle. The value of 240msec is well coincident with the simple reaction time for the Model Human Processor proposed by Card et al. These results are useful to design a Man-Machine-Interface and manage its priority under a multitask environment.

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Classification of body form is needed to design an industrial product that fits to human body shape. The conventional methods using principal component analysis or cluster analysis do not provide enough information for designing product shape. In the present study, a new method is proposed to analyze human body shape. By the procedure that each point of data of an individual body anatomically corresponds to that of another individual body, a human body shape is automatically deformed to coincide with another body shape using the Free Form Deformation method. The inter-individual distance is defined by using the FFD deformation function. The obtained deformation function can also be applied to a product shape. For example, 3D foot shapes of 17 adult females are analyzed using the present method. The distance matrix is analyzed by multidimensional scaling. The variation of foot shape is well described by the two principal axes contrasting the narrow-wide difference and the flat foot-high arched foot variation. The FFD deformation function from a foot of average width into a very wide foot is applied to a shoe last of average width. The obtained last reflects the differences in proportion between the narrow and wide feet of the same foot length better than the existing wide last.

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Heart rate variability (HRV) involves harmonic components and fractal components which are inversely proportional to their frequencies. The harmonic components with high frequency above 0.15Hz are associated with the respiratory cycle and reflect solely the parasympathetic activity, whereas the low frequency components below 0.15Hz are related to the baroreceptor reflex and are both sympathetically and parasympathetically mediated. The fractal components seem to have significant implication in the cardiovascular control center in the brain. However, their presence would result in the obscure harmonic components. Yamamoto and Hughson developed a useful spectral estimation method named the “Coarse-Graining Spectral Analysis (CGSA)” to selectively eliminate the fractal components. However, the CGSA method includes several incorrect processes in its algorithm. The present investigation proposes a corrected algorithm for eliminating the fractal components from HRV that is referred to as the “Fractal Decomposition of Power Spectrum (FDPS)”. It is clarified that the FDPS method is more sensitive to determine the harmonic components in HRV spectrum compared with the general spectral analysis. The proposed spectral analysis seems to be a useful way to assess the cardiovascular function particularly in elderly persons and patients with autonomic dysfunction whose HRV is reduced.

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Pain threshold measurements have been tried as the dosed energy density or the duration of stimulation time with a variety of thermal dolorimeters. However, the combination of a low-output Ar laser and a thermography enables to stimulate without contact and to measure the thresholds by skin temperatures. This paper propose the thermal pain threshold measurement system by this principle. We measure temperature thresholds on three subjects. As the results, the coefficients of variation in this technique are much smaller than ones in the traditional thermal dolorimeters and then it is suggested that the method in this study have a high reliability.
Additionally, the 2-dimensional heat transfer simulations are executed to estimate temperature on the surface and in the deeper part of the skin. The simulated results on the surface temperature fit well to the experimental value, and the results of deeper part of skin represent the efficiency of Ar laser in comparison with the case of CO₂ laser stimulation.

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