[Population-based study of leisure time physical activity]

To estimate the frequency of persons who are physically active in their leisure time and the quantity and intensity of their activities in relation to age, sex, body mass index and socioeconomic status in the adult population of Navarre (Spain).

We performed a cross-sectional study in an age and sex stratified random sample of the population aged 35-84 years old (1,893 men and 2,275 women). The response rate was 73.4%. The Minnesota Leisure-Time Physical Activity Questionnaire, previously validated for the Spanish population, was used. Two definitions of "physically active" were employed: a) total leisure-time energy expenditure of > 300 metabolic equivalentes (METs)/day, and b) physical exercise in activities expending >or=4 METs for at least 25 min/day for women and 30 min/day for men.

When both definitions were applied, approximately half the population aged 35-84 years old were active in their leisure time. The prevalence of physically active persons (> 300 METs/day) decreased after the age of 65 in women and no differences were found according to body mass index, educational level or occupation-based social class. In men, being active in their leisure time was related to age 65-74 years and medium or low social class.

The population subgroups most susceptible to interventions aimed at promoting leisure-time physical activity in Navarre consisted of women over the age of 65 and men of high social class.