Original article

Background Leisure-time physical activity (LTPA) has been associated with better mental and physical health particularly in cross-sectional studies. Purpose To longitudinally assess the association between LTPA, changes in LTPA and health-related quality of life (HRQL). Methods Cross-sectional and prospective analysis of the Seguimiento Universidad de Navarra Project, a dynamic cohort study. Information is gathered through mailed questionnaires biannually since 1999. A validated LTPA questionnaire was used to assess LTPA level at baseline. Changes in LTPA were ascertained at 2 and 4 years of follow-up. HRQL was assessed at 4 and 8 years of follow-up with a validated Spanish versio