Akio Nakagawa

Physical fitness of lower limb amputees.

Chin T, Sawamura S, Fujita H, Nakajima S, Oyabu H, Nagakura Y, Ojima I, Otsuka H, Nakagawa A: Physical fitness of lower limb amputees. Am J Phys Med Rehabil 2002;81:321–325. Objective To investigate the cardiorespiratory endurance of the physical fitness of amputees and able-bodied subjects of the same ages and to demonstrate deterioration of the physical fitness of the amputees. Design The test subjects were 31 amputees. Eighteen able-bodied persons served as controls. The incremental exercise test was performed to evaluate physical fitness. Sixteen of 31 amputees underwent endurance training by using a cycle ergometer driven by the intact leg, and their physical fitness was evaluated after completion of the endurance training program. Results The &OV0312;o2max, anaerobic threshold, and maximum workload for the amputees were significantly lower than those of the able-bodied group. The equivalent values for the endurance training group before exercise treatment were 18.0, 12.1, and 63.9, respectively. After exercise treatment, these values significantly increased, and there was no significant difference from the able-bodied subjects. Conclusions This study showed that the physical fitness of amputees was clearly lower than that of the able-bodied subjects and that the amputees were able to recover from a poorly conditioned status after endurance training.

VO2max as an indicator of prosthetic rehabilitation outcome after dysvascular amputation

In this study, independent ambulation of at least 100 metres with/without a cane was regarded as successful prosthetic rehabilitation. The subjects were classified into two groups according to this criterion at the time of discharge. The successful group attained this performance, the other group failed to reach this level. The successful group included 8 unilateral trans-femoral amputees aged 72.2 ± 2.1 years who underwent amputation at more than 70 years, and succeeded in walking with a prosthesis. The group which failed included 9 unilateral trans-femoral amputees aged 63.2 ± 2.1 years who underwent amputation between the ages of 60–65 years, and had great difficulty in walking with a prosthesis. The purpose of this research was to investigate whether or not %VO2max as an indicator of physical fitness is useful in predicting prosthetic rehabilitation outcome after dysvascular amputation by comparing these two groups. Evaluation of physical fitness was conducted before the subjects began prosthetic rehabilitation. Information about each subject before fitting with a prosthesis was collected retrospectively from clinical charts made during admission. The successful group were capable of strenuous exercise, reaching the intensity of 50% V02max or more. In the group which failed only one reached the intensity of 50% V02max. The working capacity of 50% VO2max or greater would appear to be a valid initial guideline level of physical fitness at which an amputee can expect to succeed in walking with a prosthesis. Apart from physical fitness, a lesser number of comorbidity, good ability to stand on the remaining leg, and a strong will to walk were found to be important factors contributing to successful prosthetic rehabilitation. This study also showed that age alone was not an important factor.

The efficacy of physiological cost index (PCI) measurement of a subject walking with an Intelligent Prosthesis

The Intelligent Prosthesis may enable lower limb amputees to walk faster than with conventionally damped prostheses and as a result the physical burden involved in walking could be expected to be considerably higher. The aim of this study was to investigate whether or not physiological cost index (PCI) is applicable as an indicator for monitoring the amount of exercise load involved in walking with an Intelligent Prosthesis. The method used a treadmill and monitored gas exchange, ventilation and heart rate (HR) in 6 unilateral trans-femoral amputees, ages were between 17 and 34 with an average age of 23.1. The exercise protocol was as follows: for each person speeds at 0.8 times the subjects free level walking speed, 1.0 times, 1.2 times, 1.4 times and for some 1.6 times were applied. In each case the index of correlation between PCI and oxygen uptake in response to walking speed was calculated. A significant correlation was observed between PCI and oxygen uptake in each case, which indicated a close relationship between cardiopulmonary factor and energy consumption while walking. These results suggest that PCI is of use as an indicator for ascertaining the amount of exercise load in walking with an Intelligent Prosthesis.

The efficacy of the one-leg cycling test for determining the anaerobic threshold (AT) of lower limb amputees

The aim of this study was to investigate whether or not the one-leg cycling test driven by the subjects sound leg as the exercise load method is an applicable method for determining the anaerobic threshold (AT) of lower limb amputees. To evaluate physical fitness, a graded exercise test that monitored gas exchange, ventilation and heart rate (HR) was performed in 51 unilateral lower limb amputees. AT was successfully measured for 42 out of 51 subjects, an 82.3% success rate. The average AT was 12.7 ± 2.2 ml/kg/min, and the average HR at AT point was 117.7 ± 16.2 beats/min. The average peak oxygen uptake was 20.1 ± 5.6 ml/kg/min, and the average peak HR was 145.1 ± 22.4 beats/min. The peak HR exceeded the HR at AT by an average 27.4 beats/min, which indicates that a comparatively intense exercise load above the AT level is possible. The average AT was 40.9% of the predicted maximum oxygen uptake, which seems reasonable when compared to the reports of other researchers. These results suggested that the one-leg cycling test driven by the sound limb is of use as a method for determining the AT of lower limb amputees.

Development of Shear Type Compact MR Brake for the Intelligent Ankle-Foot Orthosis and Its Control; Research and Development in NEDO for Practical Application of Human Support Robot

A brake in which the magnetorheologic fluid (MRF) is used has a simple structure and good responsibility. Therefore, MR brake is expected to perform a good adaptability for human-coexistence system. Being applied in an ankle-foot orthosis, however, conventional MR brake is too large to fit. Then, in this study we developed a shear-type MR brake with multi layer disks and minute gaps (50 micrometers) to realize compactness and high performance. This paper describes the development of a shear type compact MR brake and a new controllable ankle-foot orthosis with this brake. Furthermore, we design algorithm to control an ankle. We assist gait of a patient by changing a brake force.

Development of an Intelligent Prosthetic Ankle Joint (3rd Report, Development of the 2nd Prototype with an Intelligent Prosthetic Ankle Joint and Experimental Evaluations)

It is very important to test the intelligent prosthetic ankle joint in various conditions to ensure the usability of the equipment, however, there are some difficulties to evaluate the performance of the first prototype which is controlled by a bulky system adequately for the inferior mobility of the controlling system. In this paper, a prototype with an intelligent prosthetic ankle joint controlled by a mobile system constructed from a notebook computer and a compact and light control unit was developed to enable testing experiments in various environments. Walking experiments with the prototype was carried out and the usability of the intelligent prosthetic ankle joint was confirmed.

Estimation of Lower Limb Muscle Function from Kinematic Gait Analysis and Muscle Tension Model

This article discusses a biomechanical model-based approach toward estimation of muscle function of lower limb by using planer link model and muscle tension model based on kinematic gait analysis. The muscle tension model uses the relation between isometric tension and strain by Kaufman and others, and the relation between the isotonic tension and velocity by Hatze. A link model of four elements is defined for the sagittal plane motion, and regression model by Hawkins and Hull is employed to relate the joint angles and lengths of eight representative muscles. The optimum lengths of muscles are calculated based on a minimization problem by paying attention to the qualitative EMG pattern during the stance phase. The obtained muscle tension pattern had the typical characteristics in stance phase in the case of muscle with a small index of archtecture. As a case study, the function estimation is carried out for a patient with fibula fracture, and the tension calculated by model-based approach with kinematic data of gait analysis showed the reasonable recovering process consistent with that found in the joint moments. This observation encourages the model-based estimation of muscle tension using kinematic data of gait analysis with model improvement.