Dose Response to Exercise and Cardiovascular Health
Condition: Cardiovascular Diseases; Heart Diseases
MeSH terms: Cardiovascular Diseases; Heart Diseases
Study type: Interventional

Summary: 
      To determine the minimal dose of physical activity necessary to improve cardiovascular (CV)
      health by evaluating and aerobically training 500 healthy men and women, 30-65 years of age.
    

Detailed description: 
      BACKGROUND:

      Results from the study will provide important data regarding the dose of exercise required to
      improve cardiovascular health, as described both by the NIH Consensus Conference on Physical
      Activity and CV Health and by the recent Report of the Surgeon General. The study was
      initiated in response to a Program Announcement released in October 1994 on Physical Activity
      and Cardiopulmonary Health.

      DESIGN NARRATIVE:

      Subjects were randomized into one of five groups in a 2x2 factorial design plus a usual care
      control group (n=100 in each of 5 groups). Subjects trained at a moderate (45-55 percent) or
      high (65-75 percent of maximum heart rate reserve) intensity, and at a frequency of 3-4 or
      5-7 days/week (viz., Group 1, 65-75 percent at 5-7 days/week; Group 2, 65-75 percent at 3-4
      days/week; Group 3, 45-55 percent at 5-7 days/weekk; Group 4, 45-55 percent at 3-4 days/week;
      and, Group 5, usual care control). Controls received advice from a physician to increase
      their physical activity. The subjects in Groups 1-4 participated in an exercise intervention
      using walking as the mode of training for a total of 24 months. A lifestyle model of physical
      activity was used, in that subjects could accumulate exercise minutes during the day in
      10-minute increments or more continuously (for a total duration of 30 minutes/day), and
      training was conducted where it was most convenient for the subject (i.e. at home, work or
      some combination thereof). Tests occurred at baseline (0), 12, and 24 months of the
      intervention.

      The hypothesis was that Groups 1-4 would show a significant reduction in systolic and
      diastolic blood pressure and an increase in HDL-cholesterol compared to the usual care
      control group. A second hypothesis was that that there would be significant main effects for
      both frequency and intensity, with the higher levels of each producing greater improvement on
      the major outcome variables compared to the lower levels of each dose. The study also planned
      to determine the minimal dose response to exercise necessary to elicit significant
      improvement in cardiovascular and behavioral health factors. Finally, the project included
      examination of the effects of age and level of initial test values on outcome variables to
      determine if their interactions affected the results of the intervention.

      The study also includes assessment of the effect of specific doses of exercise on the
      reduction in systolic and diastolic blood pressure and increase in HDL-cholesterol (primary
      outcomes), in addition to changes in levels of physical activity, aerobic fitness (VO2 max),
      body composition (percent fat and waist-to-hip ratio), triglycerides, and LDL-cholesterol
      (secondary outcomes). Psychological variables (depression, anxiety, anger, and perceived
      stress) and health-related quality of life are also evaluated, and the important issue of
      adherence to exercise is examined with respect to the effect of dose of exercise.
    

Intervention name(s): Exercise
Intervention type(s): Behavioral
Primary purpose: Prevention