Individual assessment of muscle fatigue and its relation to the N-repetition maximum

The main focus of this paper comprises the assessment of muscle fatigue by means of time-domain and frequency-domain parameters. Based on a simple biomechanical model time-domain parameters can be computed using measurement data recorded with an isometric muscle contraction experiment of the knee extensor muscles. Frequency-domain parameters are computed from surface electromyographic recordings. Both time-domain parameters and frequency-domain parameters are compared to the experimentally determined individual N-repetition maximum of healthy subjects. In contrast to the change of the median frequency it turns out that fatigue time is able to quantify muscle fatigue and can be considered as a good predictor for the individual N-repetition maximum.