[in Japanese]

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[in Japanese]

View full abstract

[in Japanese]

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[in Japanese]

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[in Japanese]

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In the early 21st century, Japan will become a super-elderly society with approximately 25% of the population over 65 years old. It is expected that the advanced technologies such as robotics and mechatronics will be applied to the medical, rehabilitation, and healthcare areas as a means of improving the cost performance of rehabilitation. Strokes have been one of the most serious diseases in Japan affecting 1.47 million people, the elderly making up a large proportion of this number. Recovering walking function is an important goal in the rehabilitation process for stroke patients. Therefore we have developed a rehabilitation system for the lower extremities of stroke patients from 1999 to 2003. This rehabilitation system aims at the rehabilitation of the elderly, handicapped and/or patients with central nervous system disorder. This system facilitates recovery of lower extremity functions of the patients during the period from lying on bed to standing positions, decreases the work load of therapists and other care staff, and quantitatively evaluates the training efforts and recovery levels. The key technologies of the system are the safety mechanism to support the lower leg, the measurement and evaluation of lower extremity functions, various training pattern for patient, and the feedback functions to assist the leg motion and to feedback the information of the patient's conditions. In this paper, we described this system, fitting and gait results of some stroke patients, and clinical trial test results to recover walking function of them. As preliminary experimental results, walking functions of stroke patients were found to have a tendency to recover.

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Recent studies have shown that gait variability is increased in frail older adults and patients with neurologic disease. We examined the variability in stance duration among 70 female patients who had unilateral osteoarthritis of the hip (hip OA) and 33 age- and gender-matched normal controls. Stance duration was determined from trunk acceleration during walking along a corridor. There was not a significant difference in the coefficient of variance (CV) between the unaffected side of patients and control subjects. However, in patients, the CV of the affected side was significantly higher than that of the unaffected side. Furthermore, the CV of the affected side was negatively correlated with the root mean square (RMS) of acceleration, an index of trunk sway. These results may suggest that gait variability is altered in patients with hip OA. The relationship of gait variability to trunk sway may indicate that gait variability reflects disability of environmental adaptation.

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Swimming is a suitable sport for physically disabled, since the gravity is canceled by buoyancy in water and the whole body can be trained through it. However, physical disability may worsen swimming form and body balance. In this paper, the effect of amputation of the upper limb on the front crawl swimming was first analyzed by simulation, since the front crawl swimming is the most common swimming stroke and its thrust is mainly generated by the upper limb motion. Next, a swimming orthosis which compensates for the effect of amputation was designed by an optimization method for the above-elbow amputation. Finally, the swimming orthosis was manufactured based on the result of optimization and its validity was confirmed by subjective experiment.

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It is well known that neurons in the sensorimotor cortex of primates tend to synchronously activate and generate a pulsating motor command, and such rhythmic cortical drive induces voluntary contraction of muscles. Using frequency analysis, numerous experimental data have revealed that even a single neuron in the motor system transmits a rhythmic signal with a frequency much higher than its own spike rate, although this seems odd when we consider the sampling theorem. To prove such physiological findings, we investigated the transmission mechanism of a neural signal using both mathematical and simulation approaches. For the mathematical consideration, we sampled an analytical signal as both an evenly spaced and unevenly spaced time series in order to simulate regularly and irregularly spiking neurons. The results of the discrete Fourier transform suggest that only data sampled at irregular intervals contained the exact spectrum of the input signal under the condition where the sampling rate was even lower than the input frequency. By observing the signal structure, we concluded that harmonics-cancellation was achieved due to irregular sampling intervals. We also simulated both regularly and irregularly spiking neurons using Hodgkin. Huxley's neural membrane model. When we applied sinusoidal current inflow of 135.0 Hz to the neuron, the neuron spiked with constant intervals (this case is comparable to the regularly sampled data). In this case, the spectrum did not reflect the input signal. However, in the case of sinusoidal input with frequency of 132.0 Hz, the spectrum showed the input frequency content. The neural spike rate (that is, the output frequency), was much lower than that of the input frequency. From these results, we concluded that fluctuation of spiking in neural output might play an important role for transmitting information in the input signal.

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The purpose of this study was to develop a portable digital muscle hardness meter using indentation method. The developed hardness meter comprised a potentiometer, a force sensor, a liquid crystal display (LCD), and a compact flash card. The index of muscle hardness was estimated from all of data during indentation by the least square method using a proposed model. In the first experiment, performance of the developed muscle hardness meter was evaluated. The six operators (5 male, 1 female) measured the same subject with the developed hardness meter. There is not a signiflcant difference among the operators (P>0.05). In the second experiment, the muscle hardness of the trapezius muscle and the biceps brachii were measured. There is not a signiflcant difference between the two conditions, with/without T-shirt (P>0.05). The index of the trapezius muscle and the biceps brachii increased as the contractile level increased. In conclusion, the developed muscle hardness meter had good repeatability not depending on operator's skill. And the developed hardness meter detected the muscle hardness due to the different contractile level in the biceps brachii and trapezius muscles.

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[in Japanese]

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