Inclusion Criteria:  all subjects were trainable and able to walk freely without assistance. Had vitamin D deficiency, the serum level of 25-hydroxyvitamin D (25(OH) D) was ranged from 10-20ng/mL. Did not take calcium or vitamin D3 supplements, medications for osteoporosis, antiepileptic drugs, or any medications that may affect the vitamin D metabolism in the last 5 months. The feeding method during the first two years of age for all children was bottle feeding. Mild to moderate mentally retarded, (IQ ranged from 45-70) to be able to understand and obey simple orders. free from any medical consequences for example cardiopulmonary disorders, auditory defects, and visual impairments. Had no previous history of strength training. Body mass index percentile ranged from the 50th percentile to less than the 75th percentile (healthy). The feeding method was by mouth with no special diet, with an absence of signs of malnutrition  Exclusion Criteria:  autoimmune disease. Renal diseases. Have taken any thyroid medications. Obesity. epileptic fits.