Features of Supporting the Stability of the Postural Control of Young Taekwon-Do Sportsmen with Flat-Footedness

Danyshchuk, A. T.

Vasyl Stefanyk Precarpathian National University, Department of physical therapy, ergotherapy, Ukraine

*Correspondence to: Dr. Danyshchuk, A. T., Vasyl Stefanyk Precarpathian National University, Department of physical therapy, ergotherapy, Ukraine.

Copyright © 2019 Dr. Danyshchuk, A. T. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Introduction
Maintaining balance in a vertical posture, under normal conditions, is mainly due to the regulation of the tone of the muscles of the legs, torso and neck, the contribution of the muscles of the shoulder girdle to this system is less significant [1]. The equilibrium function can be significantly impaired under the influence of the general [2] and local [3] physical load on posturally significant muscles, which is especially important for athletes. One of the main reasons for the decline in balance after exercise is physical fatigue. Fatigue can alter both peripheral proprioceptive sensitivity and central integration of sensory information, as well as the generation of muscle tension [4,5]. Thus, physical fatigue is important in regulating the equilibrium function in athletes, however, the magnitude of the changes and the rate of recovery of changes in the equilibrium indices after the same physical load on the muscles involved and not participating in maintaining balance remain little studied.

The Aim of the Research is to determine the degree of imbalance under the influence of submaximal aerobic exercise on posturally significant muscles of the lower extremities in athletes 7-14 years old with flat-footedness.

The Methods and the Organization of the Research. 50 young athletes aged 7-14 years were examined: the main group (MG) of athletes with flat-footedness - 25 people involved in taekwon-do, the control group (CG) - 25 people, athletes-taekwon-up without signs of violation of the joint apparatus of the foot (JAF). Anthropometric indicators: standing height (cm) and sitting height (cm) were determined using a medical stadiometer. The girth of the chest (cm), clinical base (cm) - as the distance between the anteroposterior pelvis in the frontal plane, leg length (cm) - as the average between the indicators for the right and left legs, from the anterior superior iliac spine to the inner ankle in the position standing was determined by measuring tape. Body weight - on electronic scales “TANITA BF-541” (Japan). The characteristic of the anthropometric parameters of the foot was carried out according to the scheme Streeter [1]. To determine the electrophysiological properties of the muscles of the leg and foot, electromyography of the anterior, minor, and posterior tibial muscles, the extensor muscles and the flexor of the big toe was performed. A set of muscles was determined by their involvement in the anterior and posterior kinematic chains of the lower limb [4], which affect the correct position of the foot relative to the longitudinal axis of the lower limb and which affect the degree of flattening of the arches of the foot. The regulation of the vertical posture was studied on the stabilographic complex “DIERS FAMUS” (“Germany”) by analyzing the oscillations of the pressure center (PC) in the static-dynamic test (Fig. 1).

Athletes were asked to stand still in the main stand on the stabilometric platform for 6 minutes in the mode: 10 s - “test” closed eyes (CE) and 10 s - “rest”: open eyes (OE). For the analysis used the linear average speed (LAS) fluctuations in the center of pressure in the rack with CE. Previously, they trained to stand in this mode for 6 minutes for the effect of learning, reducing the impact of novelty, and for determining the conditional individual norm of stabilometric indicators. The results of the last 10 s in the “test” mode of the 6-minute test were taken as the individual norm. The visual target - the white circle - was located at a distance of 1.5m from the patient at eye level. Exercise was given to “postural” muscles (bicycle ergometry). The subjects performed a stepwise increasing load on the Kettler bicycle ergometer (Germany) until the heart rate at the end of the stage reached 170 beats / min. The heart rate during operation (at 59-60 from each stage) was recorded using a POLAR S180 heart rate monitor (Finland). The load on the first stage was 50W (duration 2 min) and increased by 30W on subsequent steps with a duration of 2 min. The load mode was chosen so that the duration of the tests was the same (9-12 min). At the end of the last stage, the subjects immediately got up on the stabiloplatform, tested the equilibrium for 6 minutes in a similar mode, 10 s - “test”: CE, 10 s - “rest”: OE.

The next series of studies was carried out while lifting the body to the “toe” on the leg with more pronounced flat-footedness. After that, stabilography was performed according to the above-described protocol.

Differences in the degree of change in performance after the PWC170 test between groups were determined using ANOVA for repeated measurements in the Statistica 6 program.

Results of the Research and Their Discussion
The LAS of oscillation of the center of pressure is a fairly reliable parameter reflecting the stability of the vertical posture and the degree of stress of the equilibrium regulation function [5]. Prior to physical exertion, LSS did not differ between EG and CG. Elevated values of LSS in both groups immediately after submaximal load indicates a decrease in the stability of equilibrium under the influence of physical fatigue that develops in the muscles of the leg, which belong to the postural muscle group (Fig. 2).

The degree of increase in LSS in the groups after the load was the same, however, the duration of recovery of the stability of the vertical posture was significantly shorter for athletes of the CG (within 1 min) than in the exhaust gas (for 3 min 30 s). During the entire test, in general, athletes’ MG LAS was significantly higher than in the CG (p <0.05), which is consistent with other previously published data [6].

Ergometry with one foot also caused a significant increase in LAS immediately after exercise (Fig. 3).

Comparing the LAS values immediately after working with two legs on a bicycle ergometer and one foot when performing the “lifting to toe” exercise to failure, we can say that the degree of increase in this parameter after submaximal work was the same in both groups.

However, the recovery rate when working with one foot was significantly lower in the MG than in the CG. The period of elevated values of LAS in the MG after the load was 3 minutes after working with the legs and 4 minutes and 15 seconds after working on one leg. Thus, it can be concluded that submaximal aerobic exercise on both legs and one leg causes a decrease in the stability of the vertical posture approximately equally in each group separately.

At the same time, a comparative intergroup analysis showed that CG athletes have the best performance in terms of both LAS and recovery time after testing general endurance. Comparison of the period of recovery of postural stability after submaximal load on one leg in athletes MG with a CG showed (Fig. 4) that at the CG it is much shorter (20 s) than in the MG (1 min 40 s).

The fact of imbalance after submaximal load is associated with the development of peripheral fatigue [2- 6], and with increased activity of the cardio-respiratory system [7]. Violation of the stability of the vertical posture after the load on different muscle groups can be caused by both general mechanisms and specific ones related to the functional purpose of the muscles.

The general mechanism is probably due to the increased work of the respiratory muscles immediately after work [7], which causes an increase in body vibrations, as well as the possible general localization of fatigue in the central nervous system when working with one and two legs [8].

Also, we believe that peripheral fatigue in any muscle regions affects the central integration and analysis of incoming sensory information, which leads to a decrease in the stability of the vertical posture.

The specific mechanisms of fatigue are probably associated with the accumulation of metabolic factors of fatigue in the working muscles, which violates the sensitivity of the proprioceptive system in these muscles and, in general, postural regulation [3,4].

Explaining the decrease in the stability of the vertical posture after exertion on one leg, it should be noted that we probably could not completely eliminate fatigue in postural muscles, for example, neck and back muscles when working with one leg, because they still participated in the work and involved in maintaining balance. Consequently, part of the imbalance after exertion on one leg is also due to fatigue in postural muscles located in the upstream part of the body.

This is confirmed by electromyography data, according to which young athletes of exhaust gases experience an imbalance of electrical excitability in the muscles belonging to different myo-fascial kinematic chains within the same kinematic segment of the human body, in our case it is the calf muscles (Fig. 5).

The athlete CG electrophysiological activity in both muscles is the same, because the frequency-amplitude characteristics do not have a difference between the muscles of the anterior and posterior myo-fascial kinematic chain (see. Fig. 5.1 a, b). Conversely, in the MG athlete, there is not only a decrease in the total activity in both muscles, but also an imbalance in muscle activity between the anterior (see Fig. 5. 2 a) and back (see Fig. 5. 2) myo-fascial kinematic chain.

Such an imbalance, according to some authors [3], can serve as a foundation for the violation of the CAC and the development of flatfoot.

Conclusion
Thus, after the standard intensity of submaximal load, both on one and on two legs, the stability of the vertical posture of young athletes with flat-footedness decreases to the same extent, regardless of the degree of their participation in the postural system, however, the recovery time for stability of the vertical posture is less after work on the bicycle ergometer. The recovery rate of postural stability impairment in athletes taekwon- up without disturbing the foot apparatus after a load on a bicycle ergometer is 4 times, and after working on one leg more than three times higher than that of young athletes with flat- footedness.

Such studies are of practical importance, because in different sports, simulators are used for endurance training. Therefore, knowledge of the laws of recovery of the body will allow them to be taken into account when planning training modes.

A call for future research. The following studies will be devoted to determining the possibility of correction of flatfoot taekwon-up exercises.

Conflict of Interest
The authors state that there is no conflict of interest.

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