Apply It! • A majority of youth worldwide do not accumulate at least 60 minutes of moderate to vigorous physical activity daily. • The pediatric inactivity triad is a novel construct that consists of three interrelated determinants, namely, exercise deficit disorder, pediatric dynapenia, and physical illiteracy, that drive physical inactivity in youth. • Developmentally appropriate and inherently enjoyable exercise interventions are needed to move inactive youth toward the pediatric activity triad. • Youth fitness specialists who understand the science of pediatric exercise as well as the art of designing youth fitness programs are more likely to be successful.