Aims: Strong epidemiological evidence indicates that physical activity is highly beneficial for health. To follow physical activity trends and correctly target interventions, feasible, reliable and valid assessment methods are needed. This paper examines Swedish women's understanding and interpretations of the concepts of physical activity and exercise, as well as different intensity modifiers used in the International Physical Activity Questionnaire (IPAQ). Methods: Four focus group discussions were conducted with 27 women in total aged 35 to 69 (median 52). Responses and accompanying discussion were analysed according to the principles for qualitative content analysis including both manifest and latent content in the text. Findings: Understanding of physical activity and exercise depends on differences in people's experiences. The women felt physical activity and exercise were different concepts, but ultimately agreed that physical activity and exercise were terms along a continuum of movement experiences, from informal to formal settings. The interpretations of the intensity modifiers "moderate'' and "vigorous'' were close to the formal definitions in IPAQ. However the Swedish terms "mattligt anstrangande'' (moderate intensity) and ''mycket anstrangande'' (vigorous intensity) are the best possible terms and should be used in IPAQ. Conclusions: There are different interpretations of the meaning of the key concepts in IPAQ that must be considered. The use of a qualitative approach when developing physical activity questionnaires can lead to more feasible, reliable and valid assessment methods as well as a clearer message for health-enhancing physical activity recommendations.