Recommendations for exercise prescription currently do not exist for individuals with sickle cell anemia (SCA) despite the known impact that SCA-related complications has on physical functioning and fitness. A major barrier to increasing physical activity in SCA is the concern that the well-described inflammatory effects of exercise could precipitate or exacerbate complications such as vaso-occlusive pain or airway bronchoconstriction (i.e. exercise-induced asthma). Although the investigator's preliminary data suggest that increasing physical activity may be beneficial rather than harmful in children with SCA, the pro-inflammatory effects associated with repeated bouts of moderate to vigorous exercise remain poorly understood in this population. The long term goal is to address the safety and health impact of regular exercise in children with SCA. This proposal would help establish the safety of moderate to vigorous intensity exercise in children with SCA and importantly, will inform the design of future clinical trials focused on exercise training as a transformative strategy to improve fitness and overall well-being in this population.