The Effect of Exhaustive Protocol on Knee Muscle Co-contraction in Healthy People and with a Pronated Foot during Running

Background and Aim: Fatigue and abnormalities in the lower extremities, such as the pronated foot, can adversely affect the biomechanics of human movements such as running, leading to a lack of muscle contraction and unstable symptoms in the joints of the lower extremities (knees). Therefore, the main purpose of this study was to investigate the effect of exhaustive protocol on knee muscle co-contraction in pronated and healthy individuals while running. Methods: Fourteen young men with pronated feet and 14 healthy feet participated in the study. Electromyography activities of the selected muscles before and after fatigue protocol were recorded. The statistical analysis was performed using the SPSS software and repeated measures analysis of variance (ANOVA) (P ≤0.05). Results: Findings in the pronated foot compared with the healthy foot group showed that the knee general co-contraction during the mid-stance phase (P = 0.026, d = 0.81) and swing (P = 0.046, d = 0.81) and Vastuslateralis/vastusmedialis directed co-contraction of the knee was significantly lower during the heel contact phase (P = 0.049, d = 0.81). Flexural/extensor directed co-contraction in comparison of pretest to posttest during heel propulsion phase in both groups of pronated foot (P = 0.037, d = 0.81) and healthy foot (P = 0.037, 0.81 = d) decreased significantly. The other components did not show any significant differences. Conclusion: The co-contraction of the examined muscles in the knee joint has decreased in pronated foot in different stages of stance compared to the healthy foot group. This may be due to the over-activity of a group of muscles to overcome the instability of the knee and to prevent the extra movements of this joint when fatigue occurs, and it is also possible that this over-activity of a group of muscles has affected the running mechanics of individual with pronated foot and at different stages of the running cycle caused additional pressure on the knee joint and the musculoskeletal system in the knee joint loses its ability to properly absorb shock when running, increasing joint looseness and the risk of joint damage due to fatigue Increase.