Healthy middle-school students who do not participate in team or individual competitive sports will be recruited and assessed to determine their existing predisposition toward exercise (i.e., "reluctant exercisers" and "latent exercisers"). The assessment will be conducted using three methods that have been used to measure individuals' propensity to experience positive affect in the face of a stimulus: 1) a pencil-and-paper assessment that measures tendency to respond to a challenge with positive affect; 2) electroencephalogram (EEG) to ascertain frontal cortical asymmetry; and 3) empirically assessed affective response to a standardized exercise task. Reluctant and latent exercisers will be assigned in equal numbers to one of two conditions. One condition will implement a PE-based intervention that differs from the traditional approach in that students will be instructed to exercise at an intensity that has been determined to elicit positive affect in that individual (based on baseline testing). In the other condition, students will be instructed to exercise at an intensity derived from standard formulas typically used in exercise prescriptions. It is hypothesized that the non-traditional approach will increase reluctant exercisers' enjoyment of PE and also their level of participation in physical activity outside of PE. The latter will be determined using portable monitors (accelerometers) worn at baseline, after the intervention, and again 1 year after the end of the intervention.