The Aerobics Center Longitudinal Study is a prospective study conducted at the Cooper Institute for Aerobics Research in Dallas, TX. The purpose of the study was to examine the health effects of physical activity and fitness among the general population. The cohort was established in 1970 and enrollment continues today. Each participant undergoes an extensive baseline physical examination, completes a medical history questionnaire, and has a maximal treadmill test to quantify fitness. Periodic mailed surveys are sent to the participants approximately every 5 years which gather data on health outcomes and changes in physical activity and fitness. Between 1970 and 1981 there were over 18,000 completed baseline examinations. In 1986, a mailed survey collected extensive and detailed information on musculoskeletal injuries, injury risk factors and physical activity levels. The data from this 1986 survey and the baseline examination was used is a series of studies examining the epidemiology of activity-related injuries among adults.