Volume 28, Issue 8 (11-2021)                   RJMS 2021, 28(8): 21-32 | Back to browse issues page

Research code: IR.ARUMS.REC.1397.301
Ethics code: IR.ARUMS.REC.1397.301
Clinical trials code: IR.ARUMS.REC.1397.301

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Department of physical education and sport sciences, Faculty of Educational Sciences and Psychology, University of Mohaghegh Ardabili, Ardabil, Iran , ahmad.fasihi@uma.ac.ir
Abstract:   (1379 Views)
Background & Aims: Fatigue can change the biomechanical parameters of movement by Inability to produce enough force to perform a certain motor task (1). Abnormalities in the lower extremities (such as the pronated foot) can adversely affect the biomechanics of human movements (such as walking) and cause unstable symptoms in the joints and lack of co-contraction in the lower extremities (2). In a dynamic position such as walking, from a biomechanical point of view, the simultaneous function of the agonist and antagonist muscles around the joint as well as the loads on the joint are important to maintain the position and stability of the joint (13). Due to structural changes such as increased internal rotation of the tibia and abduction of the anterior leg at the pronated foot and thus reduced impact absorption when running, fatigue may cause more pressure to be applied to the active muscles and structures involved in walking during the stance phase (10). Considering the role of co-contraction of the muscles around the knee in the control and stability of the knee joint during walking, and also due to the lack of sufficient studies on co-contraction while walking, Therefore, a more detailed study of this issue is necessary after fatigue (16). Also, recognizing the effect of fatigue on muscle co-contraction of the muscles around the knee during walking can provide a new perspective for biomechanics and other rehabilitation specialists to better implement the rehabilitation program (15). Therefore, The main purpose of this study was the effect of exhaustive fatigue protocol on knee muscle co-contraction in healthy and pronated foot individuals during walking.
Methods: Fourteen young men with pronated feet With average (age 24.66±3.29 years and height 170.52±11.66 cm and weight 66.56±15.42 kg) and 14 healthy feet With mean (age 25.27±3.14 years and height 173.7±6.2 cm and weight 72.3±4.7 kg), participated in the study. The fatigue protocol of this study was to run at the heart rate deflection point (HRDP) level until fatigue. HRDP is defined as the point of deviation of the heart rate from a straight line in examining the relationship between workload and heart rate, which is used as a criterion for planning the intensity of aerobic exercise (20). Two foot switches were used to record the time characteristics of the stance stage, ie contact of the heel with the ground and separation of the toes from the ground, one of them was installed in the outer part of the posterior part of the heel and the other was installed on the first sole-toe joint. In the classification of different stages of walking from the moment of heel contact with the ground to the moment of toe contact with the ground as the heel contact stage, the time interval between toe contact with the ground to the heel separation as the middle stage of establishment and the time interval between heel separation from the ground and toe separation (23). Electromyography activities of the Rectus femoris (RF), Vastus medialis or VM, Vastus lateralis (VL), Semitendinosus (ST), Biceps femoris (BF), Gastrocnemius medialis (GM), and Tibialis anterior (TA) muscles in two stages before and after fatigue protocol (pre-test and post-test) using (Biometrics Ltd, UK) 8-channel wireless and bipolar surface electrodes Model of surface electrode pairs Bipolar Ag / AgCl (25 mm center-to-center distance, 100 MPa input impedance, Common-mode rejection ratio (CMRR) less than 110 dB at 50 to 60 Hz) were recorded (25).To evaluate the normality of the data, Shapirovilk test was used. To compare the data between the pre-test and post-test stages of the two groups analysis of variance with repeated measures(ANOVA) and Bonferroni post hoc test were used. The statistical analysis was performed using the SPSS software version 25, the significance level was considered(p≤0.05).
Results: The results showed that after fatigue in both pronated and healthy foot groups, during the pre-test and post-test stages of walking, general knee joint co-contraction in the mid-stance phase (p=0.014) and the swing phase (p=0.032) Significantly decreased. and the Flexor/extensor directed co-contraction of the knee joint during the heel contact phase phase in the pronated foot compared to the healthy foot group, during the pre-test and post-test stages, was significantly reduced (p=0.031). and the the internal/external directed co-contraction of the knee joint during the mid-stance phase phase in the pronated foot compared to the healthy foot group, during the pre-test and post-test stages, was significantly reduced (p=0.048).Another part of the results of the present study showed that after fatigue in both pronated and healthy foot groups, during the pre-test and post-test stages of walking, the Vastus medialis / Vastus lateralis directed co-contraction of the knee joint during the push off phase, Significantly increased (p=0.012). The other components did not show any significant differences.
Conclusion: The general knee co-contraction of both pronated and healthy foot groups Significantly decreased. it seems that fatigue that occurs as a result of changes in muscle function, by changing the locomotor system can change the mechanics of movement and joints while running. Therefore, perhaps this difference in muscle activity observed after fatigue is one of the mechanisms for changes in joint mechanics and reduction of general contraction.An increase in directional co-contraction in people with pronated feet indicates an increase in pressure on the internal structures of the ankle. Long-term running may expose the internal structures of the foot to the risk of overload and injury. In general, one of the factors in the change in the degree of stability and loads of the joint can be the contraction of the muscles around the joints (22). This means that if there is a decrease in joint stability, the contraction of the muscles around the joint will change to stabilize the joint. In other words, the change in contraction is a sign of instability in the joint. Therefore, it is suggested that in investigating the effects of fatigue on walking mechanics and the incidence of walking injuries in people with pronated foot, muscle co-contraction in the joints should be considered to determine whether these changes to compensate for traumatic mechanical changes after fatigue created or related to muscle adaptation to long-term activity.
 
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Type of Study: Research | Subject: Exercise Physiology

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