Effect of thigh muscle fatigue on the biomechanical factors of the lower limbs when walking in a squatted position

[Purpose] The purpose of this study was to compare and analyze the effects of thigh muscle fatigue caused by walking in a squatted position on biomechanical factors, to evaluate the risk of a job performed sitting in a squatted position for a long period of time. [Subjects and Methods] Eighteen right foot dominant women without any injuries in their joints and body in the last 6 months were selected. They walked in a squatted position, and then muscle fatigue was induced by using an isokinetic muscular function measuring device (CSMI, USA). After the CSMI measurement, the participants performed walking in a squatted position again. [Results] After inducing thigh muscle fatigue, the knee joint maximum adduction moment significantly increased and the required duration was reduced. The muscle fatigue index was positively correlated with adduction moment and negatively with the duration. It influenced the changes of maximum adduction moment; 55.0% of the adduction moment change was explained by the degree of fatigue. [Conclusion] A quantitative analysis of working in a squatted position was performed. The thigh muscle fatigue index negatively the knee joint during walking in a squatted position. Therefore, this experiment can be used as an ergonomic analysis tool of general farm work.