aLL survivors are at elevated risk for obesity, low bone mineral density, cardiomyopathy, peripheral neuropathy, and altered psychosocial functioning. Childhood aLL survivors are also less likely than their siblings to meet recommended physical activity guidelines (48% vs. 52%) and more likely to lead an inactive lifestyle. among childhood cancer survivors, an inactive lifestyle increases the risk of developing hypertension, dyslipidemia, diabetes, and obesity by almost 70%. additionally, cancer survivors are 4.2 times more likely to die of a cardiac event than members of the general population. Physical activity interventions may be able to stimulate habitual physical activity, improve cardiopulmonary and musculoskeletal function, normalize metabolic biomarkers, decrease fatigue, and improve quality of life and school attendance if initiated soon after treatment for childhood aLL. The study plans to evaluate if the effect of the intervention on markers of cardiometabolic health is mediated by changes in fitness. To achieve this goal the study will utilize a two-arm, prospective, randomized study with an intervention group (n[?]192) and a control group (n[?]192).