BACKGROUND:
The primary goal of the Dose-Response to Exercise in Women aged 45-75 Years (DREW) was to investigate the effects of different amounts of exercise on both cardiorespiratory fitness and risk factors for cardiovascular disease. Participants were sedentary, overweight or obese, postmenopausal women who had high normal blood pressure or Stage I hypertension, and thus are at moderately high risk for cardiovascular disease. A total of 464 women (about 35% were recruited from minority groups) were randomly assigned to a control group (N = 102) or to 1 of 3 exercise groups (N = 155 for the lowest exercise dose and 104 in the 8-kcal/kg group and 103 in the 12-kcal/kg exercise group). Women assigned to the exercise groups exercised for 6 months at energy expenditures of 4, 8, or 12 kcal ·kg-1 · week-1. These exercise doses represent the consensus public health recommendation for physical activity from recently published guidelines from the U.S. Public Health Service, American Heart Association, and American College of Sports Medicine (8 kcal ·kg-1 · week-1) and at doses 50% below (4 kcal ·kg-1 · week-1) and 50% above (12 kcal ·kg-1 · week-1) the consensus dose. All women exercised at 50% of V02 max. The exercise sessions took place in the exercise laboratory, with individual supervision of each session and strict control of frequency, duration, and intensity. This was provided thorough documentation of the exact amount of exercise completed. Primary outcome measures are VO2 max and resting systolic blood pressure. Other cardiovascular disease risk factors, psychosocial variables, health-related quality of life, body composition, and fat distribution are secondary outcomes. Other secondary analyses included a focus on the extent to which observed dose-response effects are modified by baseline levels of fitness, ethnicity, risk factors, or age. Assessments will take place at baseline and 6 months. The research provided information about (1) patterns of change in outcomes produced by each of several exercise doses, (2) whether performing exercise at less than the current consensus dose has any benefit, (3) whether performing more exercise than the consensus dose has greater (or proportionally greater) health benefits, and (4) the characteristics of sedentary women who are most likely to benefit from various exercise doses.
DESIGN NARRATIVE:
A total of 464 sedentary, postmenopausal women at moderate risk for cardiovascular disease was randomly assigned to receive exercise training at one of three doses (4, 8, or 12 kcal/kg/wk) or no exercise for six months duration. The specific aims were be to determine: (a) if women in the exercise groups have increased aerobic power (VO2max) over the six months compared to the no exercise group; (b) if women in the exercise groups have a greater reduction in resting systolic blood pressure than those in the no exercise group; and, (c) if there will be a dose-response gradient across the three exercise groups for changes in aerobic power and systolic blood pressure. Secondary aims include evaluating the effects of exercise dose on fasting blood lipids and lipoproteins, glucose, insulin, anthropometry, self-reported quality of life, and cardiovascular risk as determined by a multiple logistic risk function. Covariates to be controlled included dietary intake, physical activity (outside of the exercise program), smoking, alcohol intake, sleep habits, medication use (including hormone replacement therapy), demographics, menstrual history, personal and family medical history.
