Design. This was a 10-wk intervention study. Previously sedentary women were randomly allocated to a brisk walking group or to a control group after baseline tests were completed. The protocol was approved by the Ethical Committee of the University of Ulster and each volunteer gave her written consent after a full explanation of the procedures and risks. Measurements were made at baseline and again 10 wk later by the same experienced observer. After baseline testing, women were allocated to one of three groups, ie, short-bout walking, long-bout walking, or usual life-style (control). All subjects agreed not to change their diet.

Subjects. Forty seven women aged between 31 and 57 yr were recruited by advertisement from the University of Ulster and the local community. None was employed in manual work and none had engaged in regular physical activity (defined as more than one 20-min bout per week) during the preceding 6 months. Exclusion criteria were: history of cardiovascular disease; resting arterial blood pressure> 150 mm Hg systolic or> 95 mm Hg diastolic; body mass index≥ 30 kg· m-2; diabetes; musculo-skeletal condition or injury; taking any pharmacotherapeutic drug. Thirteen women dropped out because of illness (one control, one long-bout walker), lack of interest (four controls, one short-bout walkers), or time pressures (three short-bout walkers, three long-bout walkers). Dropouts did not differ with respect to age, BMI, or VO2max from subjects who completed the study. Data are presented for the 34 women who completed the study (12 short-bout walkers, 12 longbout walkers, 10 controls).