One hundred and twenty-five healthy children ( @ boys , @ girls ) , aged @-@ years old ( @ @ years ) , who were self-assessed as belonging to Tanner stages I and II , were randomly divided into two experimental groups , a strength training group ( @ boys , @ girls ) and an endurance training group ( @ boys , @ girls ) that would train twice a week for @ weeks , as well as a control group ( @ boys , @ girls ; no training program ) .