Although different indicators of physical activity and different methods of analysis are used, it appears that physical activity tracks at low to moderate levels during adolescence, from adolescence into adulthood, and across various ages in adulthood. Tracking of inactivity is less often studied. Measures of performance- and health-related physical fitness (strength, flexibility, motor fitness, aerobic power) track significantly across childhood and adolescence, but correlations are low to moderate. Limited data that span adolescence into adulthood indicate somewhat higher interage correlations for flexibility, static strength, and power. Data for different periods in adulthood are not available. Presently, it is common to criticize focus on motor and sport skills in physical education and competitive sports as contrary to health and fitness goals (e.g., James, 1995; Livingstone, 1994; Simons-Morton et al., 1988). There is a need, however, to distinguish between youth or community sports and highly specialized sport for the elite. Sports activities, be they competitive or recreational, are probably the major form of physical activity during childhood and adolescence, and perhaps in young adulthood. Though low to moderate, the tracking of various activity indicators, most of which include sport participation, suggests that sport activities during childhood and youth may form the foundation for activity habits in the future.