Effect of local muscle fatigue on biomechanical and viscoelastic properties of skeletal muscles

The work is devoted to the study of the effect of local muscle fatigue on the biomechanical and viscoelastic properties of skeletal muscles. A device for non-invasive digital palpation MyotonPRO was used to carry out myotonometric measurements. The study involved 13 males and females (6 males and 7 females) aged 32.5 ± 10.6 years. Each volunteer completed two series of exercises that induce local muscle fatigue of the hand muscles. The exercises were performed with a hand grip with a resistance of 20 kg. The first series of exercises was performed until the volunteer developed a subjective fatigue, the second - until his/her refusal to continue due to excessive fatigue of the hand muscles. Testing had 3 stages: before starting strength exercises, after exertion, before subjective fatigue, and after loading with maximal exertion. Local muscle fatigue was objectively confirmed by dynamometry in accordance with the physiology standards. Myotonometry was performed on the cubital and radial flexors of the carpus, and on the abductor thumb muscle. As a result of the statistical analysis of data, it was shown that the myotonometry can be used to diagnose muscle fatigue. A change in active muscles myotometric indicators can be registered even when a subjective fatigue occurs, while local muscle fatigue does not affect the change in the tone of inactive muscles. It was also shown that the location of the measurement point of myotonometric characteristics on the muscle belly of the cubital flexor of the carpus does not affect the results with the condition that the place of application of the device is within the range of ±2 cm from the center of the muscle belly.