The mutual effect of fatigue and sole structure on the kinematic characteristics of walking

Master's thesis in the field of physical education and sports sciences, sports biomechanics orientation

Abstract:

Flat feet are among the most common abnormalities. Anatomical anomalies can change the kinematic variables of the leg joints, which results in a different walking pattern. Identifying the quality and quantity of the variables affected by these anomalies is effective in the rehabilitation of people with flat feet. Due to the change in the length-tension relationship in the leg muscles of a person with flat feet, there is a higher possibility of fatigue in these people.  Since there are few studies on the effects of fatigue on the kinematic changes of walking, the results of this study can provide useful information in this field. The aim of this study is to investigate the effects of fatigue on the changes in the kinematic pattern of the lower limbs of people with flat feet compared to healthy people while walking. The number of 10 male students with the average age (24.4 ± 2.16), the average height (177.26 ± 4.31) and weight (93.81 ± 17.43) in the group of people with flat feet, as well as the number of 10 male students with the average age (25.86 ± 2.32), the average height (168.6 ± 27.71), and the average weight (26.93 ± 26) 78/13) were studied in the control group - healthy people. First, people's leg, leg, thigh and pelvis were identified using 16 light-reflecting markers. Then the subjects walked in a calibrated path and using the VICON motion analysis system, the kinematic variables of the wrist, knee and hip joints were measured and analyzed. The size of the markers is 14 mm in diameter and they were installed on the body based on the PLUG-IN-GAIT model. Each subject repeated the walking test 5 times. The subjects were then fatigued using a functional fatigue protocol. Multivariate analysis of variance was used to compare the pre-tests between the two groups and also to check the amount of changes between the groups. Data analysis was done in SPSS 18 with a significance level of p=0.05. After fatigue, the walking test was repeated for each subject.  Statistical analysis showed that during the pre-test, in people with flat soles, the range of motion of the right ankle joints in propulsion (p=0.00), right knee in mid-stance (p=0.007), right thigh in mid-stance (p=0.002) and propulsion (p=0.008), left ankle in mid-stance (p=0.00), left knee in propulsion (p=0.024), left leg thigh in contact with the heel (p=0.001) and middle stance (p=0.05) are more than normal people. Also, in people with flat feet during the pre-test, the range of motion in the right ankle at heel contact (p=0.014) and the right knee in the middle of stance (p=0.02) was lower than normal people. During the pre-test, people with flat feet had a longer stride length than normal people (p=0.02). In normal people, in the post-test, the range of motion of the hip joint of the right leg in mid-stance (p=0.037) and the thigh of the left leg in propulsion (p=0.00) and mid-stance (p=0.00) was more than the pre-test of these people. In people with flat feet, in the post-test, the range of motion of the right thigh in contact with the heel (p=0.039) and mid-stance (p=0.042) and the range of motion of the left leg in contact with the heel (p=0.015) were higher than in the pre-test of these people. The range of motion of the left knee of people with flat feet was higher in the pre-test than in their post-test (p=0.00). People with flat soles in the post-test had faster walking speed in the right leg (p=0.049) and left leg (p=0.049), longer stride length in the left leg (p=0.017) and shorter stride time (p=0.02) compared to the pre-test. The comparison of the joint range of motion between the two groups showed that the range of motion of the joints of normal people in the left thigh, in mid-stance (p=0.00) and in propulsion (p=0.00) is greater than that of people with flat feet, and in the knee joint, people with flat feet have more range of motion in propulsion than normal people (p=0.00)..

Key words: flat feet, fatigue, walking kinematics

-1. Introduction

Today, in equipped biomechanical laboratories, various aspects of influencing factors in controlling posture and walking are discussed in order to gain a better understanding of the effect of these factors on walking parameters. Walking is one of the complex human tasks that requires a combination of skeletal and neuromuscular systems. When the function of these systems is damaged or their coordination is disrupted, they cause changes in the biomechanics of human walking and motor control (Winter, 1991, 1994). Everyone believes that many foot injuries are caused by pasteurian deviations[1], "deviations in the structure of the foot that cause more or less range of motion and subsequently prevent proper stability and mobility when walking". For example, foot structure is often known as a risk factor for the development of some common foot and ankle injuries, stress fractures in the lower limbs, posterior tibial tendinitis, central heel pain, Achilles tendonitis, and plantar fasciitis among other factors. has the The human foot is the only place where the body comes into contact with the ground during movement, and foot posture can play an essential role in how the force of the ground reaction is distributed in the organs. Muscle fatigue occurs during daily work or sports and rehabilitation activities (Cifrek et al, 1999).

The quadriceps muscles are considered to be the largest muscles in the body and during movement activities they play an essential role in producing movement and absorbing contact forces during foot contact with the ground (Hamil & Knutzen, 2009). Deviations from the natural posture have affected the main role of the foot, which is the proper transfer of action and reaction forces between the body and the ground, and can cause foot inefficiency and subsequent damage to the lower limbs. In this research, the researcher aims to determine the kinematics of these traumatic changes by applying fatigue.

1-2. Defining the problem and expressing the main points

Since the foot is the most important means of interaction between the earth and the human body, the structure and type of anatomy of the foot is an influencing factor on walking (Ledoux and Hillstrom, 2002). So that any deviation in the legs transmits its effect in a chain-like manner to the joints and upper limbs. Abnormal alignment of the foot theoretically causes abnormal movement of the foot while walking. Therefore, the occurrence of abnormalities in this area is biomechanically important (Zifchockand, 2008).  One of the most common abnormalities of the foot area is flat feet (Lee, Vanore et al., 2005). Many factors affect the biomechanics of walking, such as neuromuscular diseases, brain-spinal lesions, ligament-joint injuries, and fatigue, which can change kinetics, kinematics, muscle activity patterns, and energy consumption during walking (Winter, 1991; Yoshino, 2004). Movement is one of the main aspects of life, and walking, as a basic skill, is the most part of human daily movement activity (Winter, 1991, 1995). Fatigue is one of the properties of muscles, the result of which is a decrease in the performance of metabolic and neuromuscular systems for the continuation of activity. Fatigue reduces the willpower and functional capacity of muscles, disrupts the simultaneous activation of agonist and antagonist muscles, and ultimately reduces the performance and efficiency of the neuromuscular system. Fatigue of the muscles around a joint (local fatigue) can cause a change in the movement pattern, a change in the contraction of the muscles of that joint, a change in the sense of the state of the joint and, as a result, an increase in the risk of injury Paillard, 2012 (Walsh et al, 2011; Davidson, 2009). These muscles are very important in the production of power of the lower limbs for moving the body and may be exposed to excessive use during various activities and as a result local fatigue (Pincivero et al, 2006; Hamil & Knutzen, 2009). Fatigue of these muscle groups can cause kinetic and kinematic changes of the lower limb during walking (Parijat & Lockhart, 2008). Flat feet is a condition in which the internal longitudinal arch, which covers the entire inner part of the foot, is lost or reduced (Chen, et al., 2010).