Assessment of muscle fatigue by NIRS

Abstract

Recently, evaluation of muscular fatigue and the fatigue recovery level is needed in the fields of medical treatment, welfare and work place, etc. In order to prevent bodily damage resulting from working and improve the efficiency of rehabilitation for occupational injured people, an accurate and simple method of evaluation of muscular fatigue is preferred. There is also a need for assessing the effectiveness of physical training treatment for physically handicapped people by analysing the data of muscular fatigue. Besides the personal needs of individuals, many companies in labor-intensive industry find it is essential to apply the assessment of muscular fatigue for manual workers during production to prevent economic loss and the reduction of labour force occurred by occupational diseases. However, there are no method nor apparatus which measure the muscular fatigue precisely and easily so far. The most commonly used method for the assessment of muscular fatigue is detecting the frequency transition of electromyogram (EMG), but it has certain drawbacks of being complicated and less efficient. Moreover, the fatigue may not be detected in isotonic contraction using the current method. In this study, a new method of measuring the muscular fatigue is investigated. We propose to apply near-infrared spectroscopy (NIRS) to measure the amount of oxygenated hemoglobin and deoxygenated hemoglobin and define the result data as a new index, ΔHbt, for evaluating the muscle fatigue. The validity of measuring ΔHbt to assess the muscular fatigue is shown by comparing the experimental results of using EMG and NIRS evaluations.