Letter: The benefits of exercise.
D002648:Child; D002675:Child, Preschool; D006801:Humans; D007231:Infant, Newborn; D005082:Physical Exertion; D012141:Respiratory Tract Infections / Q000209:etiology / Q000517:prevention & control*; D013122:Spinal Diseases / Q000209:etiology / Q000517:prevention & control*