Cerebral palsy is one of the most common neurological disorders caused by non-progressive brain lesion influences the abilities of the children to stand and walk (4, 5). The ability of children with CP to stand and keep their COM within the base of support decreases compared to normal subjects (7, 20). One of the exercises used to improve the stability of CP patients is core stability test. There is no evidence regarding the effects of this exercise on stability of subjects with CP. Therefore, the aim of this study was to evaluate the influence of this exercise on stability of CP patients.
The results of this research study showed that the mean value of ApEn of the patients was significantly less that of normal subjects. Based on the results of various research studies lower value of approximate entropy associated with decrease in complexity. This represents that the system is too rigid and too unstable. Therefore, it can be concluded that higher value of approximate entropy in CP patients compared to normal subjects represents unstability of CP children. It means that their neuromuscular system had a lower adaptability and is too rigid. The main reason related to spasms of lower extremity musculature.
Although in most of research studies on stability of CP patients, the stability was measured by use of berg balance scale or by use of force plate based on linear approach, however most of them confirm that the CP subjects are more unstable than normal subjects. The impairment in gait and stability of CP subjects may be due to changes in mechanical properties of muscle tendon system, impairment muscles activation, loss of selectivity in neuromuscular output and abnormal velocity dependent of muscles activity(8, 29, 30). It should be emphasized that in this research, nonlinear analysis approach was used which specifically represent the quality of stability.
As can be seen from table 3, the mean values of ApEn of CP patients increased follow core stability exercise. The main reason to use this exercise is to improve the function of abdominal muscles, pelvic and shoulder to assist in maintaining of posture (15, 31). Increase in ApEn interpreted as increase automaticity of postural control and also efficiency of postural control. Therefore, it can be concluded that the stability of CP patients improved in both planes follow a period of core stability exercise. The interesting points were that the spasm of hip joint flexor, adductor, knee flexor and ankle plantar flexor decreased follow the use of this exercise. It can be emphasized that stability of CP patients improves by use of this exercise due to its influence on lower extremity musculature spasm.
Berg Balance Scale was also used in this study. Actually this is a 14 items scale designed to measure balance of elderly and handicapped subjects in a clinical setting (25). A high record of this scale (Maximum 56) indicates less impairment in balance function. As can be seen from table 3, the records of Berg Balance Scale test of CP patients improved significantly follow use of core stability exercise. Therefore, it can be concluded that not only static stability of CP subjects improved (determined by use of ApEn), but also the dynamic stability of the subjects improved as well.
There is no study on use of core stability exercise on stability of CP subjects. However, the results of the research done by Kim et al on hemiplegic subjects (46-75 years old) shown that core stability exercise is effective to improve static and dynamic stability (15). Balance training exercise with and without visual feedback was also studies in some researches (11, 21). It has been shown that balance training exercise improves standing stability and increases the amplitude of voluntary weight shift. Some benefits of balance training exercise include: faster activation of the muscles, faster stability recovering, and emerge of a distal proximal muscle sequence (11).
The results of this study represented that stability of CP subjects, static and dynamic, improved significantly follow a period of exercise, however, there were some limitation which should be acknowledged. The main limitation associated with this study was the number of subjects. Furthermore, dynamic stability did not measure during walking. Therefore, it is recommended to do the same study on big number of subjects and also it is recommended to evaluate stability during walking.