Effects of Grip-Load Force and Muscle Fatigue on fNIRS Signal during Handgrip Voluntary Contraction Task

The studies of grip-load force and muscle fatigue characteristics are of great significance in rehabilitation and sports medicine. Functional near-infrared spectroscopy (fNIRS) is generally used to investigate cerebral oxygenation changes during a motor task. In this study, the effects of force load and muscle fatigue on fNIRS signal features during a handgrip voluntary contraction task were quantitatively investigated. Twenty-four healthy subjects performed isometric grasping contractions at the conditions of 30% and 50% of the maximal voluntary contraction (MVC) with his/ her dominant or non-dominant hand. Experimental results showed that the average change rate of oxygenated hemoglobin (HbO(2)) concentrations at the condition of 30% MVC hand muscle strength was significantly smaller than that at the condition of 50% MVC hand muscle strength. However, the total change of HbO(2) concentration in conditions of the 30% and 50% MVC hand muscle strength were in good agreement. The total change of HbO(2) concentration and the average change rate of HbO(2) concentration were not significantly different between the dominant and non-dominant hands.