عنوان مقاله [English]
Background and Aim: One of the most important parts of the spine is the lumbar arch. Due to the close connection of the lumbar vertebrae with the pelvic, especially through the sacrum, any change in the position of the pelvic leads to a change in the amount of this arch, and subsequently, any increase or decrease in the amount of the angle of this arch affects the balance. It affects the body and causes various abnormalities in the lumbar-pelvic area. Controlling posture or maintaining balance is one of the key components of success in daily activities and sports activities. It is a dynamic process that acts as a closed-loop system to maintain the position of the center of gravity above the support surface, resulting in postural sway within this range. It requires continuous examination of sensory inputs from different parts, their processing in the central nervous system and appropriate motor response in order to establish a balance between stabilizing and confusing forces. Postural sway is evaluated according to shifting the center of body pressure which affects the body's center of gravity position and directly is in the relationship with body control and balance. Several factors are involved in proper controlling of postural sway and consequently in maintaining balance that among the most important of them can be noted to core stability. This area has many muscles that stabilize the pelvic girdle, establish the movement of the organs and provide the optimal control of the movements with the proper transfer of force, change of weight direction and pressure distribution. According to the research results, the strength of the core muscles in women is less than men. Weakness of core muscles cause an interruption in the transfer of energy from the trunk and limbs to each other and this leads to decrease athletic performance and increase the possibility of injury. Postural abnormalities, increased lumbar lordosis, can change the alignment of the lumbar-pelvic region and cause changes in muscle activity patterns and the occurrence of muscle imbalances, which may cause dysfunction of the core muscles. Therefore, the proper ability to control the posture is necessary and important for physical performance and many sports activities, and the efficiency in controlling the posture can guarantee the successful performance. In some sports, including taekwondo, this transmission is of great importance. Because in taekwondo, many movements are performed in an open kinetic chain. Also, in the background literature, increased lumbar lordosis has been mentioned as one of the most common abnormalities in young women and taekwondo athletes. Kim et al. (2011) stated that kicks in taekwondo include hip flexion and knee extension, as a result of continuous use of quadriceps muscles and also psoas in these movements leads to an increase in strength in these muscles ,that is the reason for increasing lumbar lordosis in taekwondo athletes compared to non-athletes.The negative influencing factors on the performance of the core muscles in the Taekwondo player are the occurrence of muscle imbalances following the presence of postural abnormalities. The aim of the present study is to answer to this question that is there any difference in level of Postural sway and core muscle endurance in taekwondo female athletes with or without hyper lordosis.
Materials and Methods: The target society was professional Iranian female taekwondo athletes among whom 60 athletes were purposefully selected and divided into two groups of 30 members: with hyper-lordosis (age: 22.17±2.35, height: 166±3.95, weight: 55.37±5.53) and without hyper-lordosis (age: 20.63±2.38, height: 165±4.23, weight: 53.7±4.91). Postural sway was measured by means of force distribution for single leg, core muscle strength was measured by testing core stability McGill. In this research, a 30 cm ruler was used to measure lumbar lordosis. Independent t-test was used for comparison results and confidence interval and P-value were 95% and 0.05.
Results: Independent t-test results showed that there is a significant difference between the two groups only in endurance of abdominal flexor muscles (p=0/013) but there was no significant difference between the other tests of core muscle endurance (P=0.76), postural sway based on two factors of length (P=0.30) and area (P=0.16) displacement in two groups.
Conclusion: The aim of this study was to compare the endurance of core muscles and postural sway in taekwondo female athletes with and without increased lumbar lordosis. The analysis of the research findings showed that the only significant difference between two groups was seen in trunk flexor muscle endurance and the other research variables were not significantly different in the two groups with and without increased lumbar lordosis. Based on the background of the research, it was expected that due to the changes in the curvature of the spine in the lumbar-pelvic region (increased lumbar lordosis), the pattern of muscle activity in this region would change and with the occurrence of muscle imbalances, the endurance of the core muscles and the stability of the this region in two groups with and without Increased lumbar lordosis is different. According to the results of this study, the endurance of the abdominal flexor muscles in taekwondo female athletes with hyperlordosis is weakened and there is a difference in the endurance of the flexor muscles and the possibility that more changes may be made in the muscles of the core region of the body in the future based on the muscle chains, it seems that a follow-up research is necessary. And the investigation should be done over a longer period of time on this group of people. But currently, it is not possible to say with certainty whether increased lordosis abnormality has a negative effect on the amount of core muscle endurance factors and posture sway in athletes or not. Therefore, there is a need for more research in this regard. Given that musculoskeletal disorders may affect other areas of the body over time, it is recommended that long-term, follow-up research be used.
Research limitation: In the present research, the samples were from three different areas of Tehran clubs, there were many problems in order to coordinate for the subject to participate in the test, that's why the testing was done at different hours of the day.