Introduction: Multiple sclerosis (MS) is a chronic disease disabling the nervous system by destroying the myelin of the central nervous system (brain and spine). The cause of this disease is still unknown. It destroys a substance called myelin and that distorts the conduction of nervous and electrical currents bringing about gradual disability of some muscles in the body (1, 2). This disease has tremendous deep effects on the lives of patients who are in need of working, making a family and living in one single word, making them suffer from countless unexpected side effects and complications that may ruin their lives (1). The most common side effects of the disease are fatigue, physical weakness, muscular spasm, shaking, imbalance, asymmetric vision, double vision or walking disorder (3). Physicians classify MS symptoms into three groups: (1) primary symptoms: those occurring directly due to the destruction of myelin in specific nerves (such as vision imparities); (2) secondary symptoms: those created due to primary symptoms, e. g. primary forms of paralysis may cause the patient's muscles to become thinner and unable to function; and (3) third type symptoms: mental, psychological and social side effects caused as a results of primary and secondary symptoms (4). Due to lack of a final cure the patients have to rely on therapies that only serve to reduce the symptoms (5). Exercise therapy may be used as a supplement to medication therapies to slow down the symptoms (6). Hydrotherapy promotes physical fitness in 5 ways: (1) giving more energy to patient and helping him sleep better, (2) controlling the patient's weight, (3) reinforcing the patient's heart muscles, (4) fighting depression, and (5) promoting self-confidence and health in the patient (7). In this study a physical disability scale ranging from slight to medium disability (1 to 4) has been used. Based on World Health Organization definition of Kurtzke or Expanded Disability Status Scale (EDSS) is any sort of restriction of fault in a person's ability to undertake normal activities which affects the performance of his duties (8). Research on MS patients started by Charcot in 1868. Rassua (2004) undertook a course of aerobic exercises for 8 weeks including 112 MS patients, and observed a significant improvement in their balance (9). Wiles (2001) conducted an aerobic exercise program in 4 weeks on 42 MS patients and observed a significant improvement of balance in MS patients whose EDSS scores were quite low Contrary to our findings,(16) Contrary to our findings, Because of the positive effects of physical activities on MS patients researchers have been increasingly attracted to using 8 weeks of selected aerobic exercises alongside medication therapies to help in the decline of MS symptoms and promotion of the patients' balance. Through such efforts the researchers expect to observe and then study significant results about the effects of selected aquatic aerobic exercise on the balance of MS patients. Eventually there is one question: "Do aquatic aerobic exercises have any effects on balance in MS patients?"
