Introduction Physical activity has been recognized to be a protective factor against coronary heart disease [3,8]. Several observational stud- ies support this association [25]. Although national and interna- tional health promotion programs encourage the general popu- lation to increase regular physical activity [8,32], a controversy exists concerning the amount and intensity required to achieve this potential beneficial effect [12]. Physical activity has been shown to improve lipid profile in men [16,18], but the evidence is scarce in women [16]. Furthermore, in childbearing-aged women the analysis is complicated by the complex relationship among physical activity, lipids, and sexual hormones [26]. The MARATDON Study (Mesura de la Activitat física i la seva Rela- ció Ambiental amb; Tots els lipids en les DONes, or Measuring phys- ical activity and its relationship with all lipids in women) was de- signed to determine the association between the total amount of Abstract The aim of the study was to determine the association between the amount and the intensity of physical activity (PA) and lipid profile and fitness in pre-menopausal women. A cross-sectional study was conducted, sampling was stratified according to two age groups and two levels of PA, as assessed by the Minnesota Leisure Time PA Questionnaire. Serum lipid profile and sex hor- mones were measured. The study included 403 women. Total en- ergy expenditure on PA was directly associated with HDL-choles- terol and inversely with atherogenic index. When intensity was analyzed, only moderate PA was associated with a desirable lipid profile. A decrease of 1.59 mg/dL (standard error [SE] = 0.77) and 0.07 units (SE = 0.02) in LDL-cholesterol and atherogenic index, respectively, and an increase of 1.02 mg/dL (SE= 0.34) in HDL- cholesterol were observed per each 100 MET·min/day spent in moderate PA. After adjusting for body fat mass, the association between moderate PA and LDL-cholesterol was no longer statis- tically significant (regression coefficient = – 1.21; SE = 0.81) whereas the association between moderate PA and atherogenic index (regression coefficient = – 0.05; SE = 0.02) and HDL-choles- terol (regression coefficient = 0.98; SE = 0.35) remained statisti- cally significant. Only vigorous PA was associated with V ˙ O 2max . V ˙ O 2max increased 2.35 mL/kg (SE = 0.39) per each 100 MET · min/ day spent in vigorous PA. Only moderate PA is associated with a lower LDL-cholesterol and atherogenic index, and higher HDL- cholesterol. The association between PA and LDL is dependent on body fat mass, but the association between PA and HDL is in- dependent of it. Only vigorous intensity PA is associated with fit- ness. Key words Cholesterol · lipoproteins · exercise · physical fitness · triglycer- ides Clinical Sciences 911 Affiliation 1 Institut Municipal d’Investigació Mèdica, Barcelona, Spain 2 Facultat de Medicina, Universitat Autònoma de Barcelona, Barcelona, Spain 3 Hospital del Mar, Barcelona, Spain Correspondence Roberto Elosua · Institut Municipal d’Investigació Mèdica · Dr Aiguader 80 · 08003 Barcelona · Spain · Phone: + 349 32 2110 09 · Fax: + 349 32 2575 50 · E-mail: relosua@imim.es Accepted after revision: November 20, 2005 Bibliography Int J Sports Med 2006; 27: 911–918 © Georg Thieme Verlag KG · Stuttgart · New York · DOI 10.1055/s-2006-923790 · Published online June 8, 2006 · ISSN 0172-4622 A. Arquer 1, 2 R. Elosua 1 M.-I. Covas 1 L. Molina 3 J. Marrugat 1, 2 Amount and Intensity of Physical Activity, Fitness, and Serum Lipids in Pre-Menopausal Women