Overview
A large body of evidence indicates numerous health benefits of physical activity, including prevention of cardiovascular disease (CVD), the leading cause of death in the US. This evidence has led to US Physical Activity Guidelines that recommend ≥150 min/week of moderate or ≥75 min/week of vigorous aerobic exercise (AE), plus resistance exercise (RE; such as weight lifting) on ≥2 days/week. To date, current research has mostly focused on AE, and we know a great deal about the dose-response relation between AE and health, resulting in clear and practical guidance to the public on the recommended "dose" in min/week. However, currently far less is known about the dose-response for RE: ≥2 days/week are recommended, but with no duration specified. Thus, this project aims to provide clarity on the dose relationship between RE and health. This project will significantly contribute to developing more effective CVD prevention approaches, advancing prescriptive intervention guidelines, by helping to fill the important gaps in knowledge on effective minimum dose, beneficial optimal dose, and safe maximum dose of RE for CVD prevention. Thus, advancing prescriptive intervention guidelines, and provide important insights for future science of physical activity and health.
Description
Participants will be randomly assigned to 1 of four research conditions at varying dosage of resistance exercise (RE) for the duration of 1 year, either 0 min, 30 min, 60 min or 120 min of weekly RE in addition to 60 min of weekly aerobic exercise (AE). Total exercise duration will be split between 2 weekly sessions. Participants in all four groups will receive healthy lifestyle education sessions, and will track daily steps, food intake and activity levels throughout the 1-year intervention. Participants will also complete baseline, 6-month, and 12-month physical examinations, which will include assessments of blood pressure, blood lipids, body composition, and aerobic and muscular fitness. During the first 6 months of intervention will occur in a supervised lab-based setting. Changes in Cardiovascular disease (CVD) risk factors, as well as potential mechanisms (arterial stiffness and inflammatory markers) that might explain a J-shaped dose-response, from baseline to 6 months will be assessed in each of the 4 groups. The second 6 months will follow the same exercise intervention as the first 6 months. However, all participants will be provided with a free health club membership. The second 6 months will be used to investigate the RE dose associated with best adherence in a free-living environment during the second 6 months. In addition, all measures taken at 6 months will also be assessed again at 12 months to examine the long-term effects of different doses of RE as secondary outcomes, given that compliance will not be tightly "enforced" by staff in this unsupervised free-living condition. In this case, the investigators will further carefully consider exercise adherence in data analysis.
Eligibility
Inclusion Criteria:
- Non-Smoker
- Overweight or Obese: Body Mass Index 25-43 kg/m2
- Inactive: not meeting the US resistance and aerobic exercise guidelines over the last 6 months
- Walking <7,000 steps/day at baseline
- Capable of performing the required exercise training
Exclusion Criteria:
Absolute
- Unstable coronary heart disease or heart failure
- Uncontrolled arrhythmias or severe aortic stenosis
- Acute myocarditis, endocarditis, or pericarditis
- Cancer, requiring treatment in the past 5 years
- Autoimmune diseases, affecting immune system
- Plans to be away ≥4 weeks in the next 1 year
- Pregnancy/anticipated pregnancy during the study
- Other medical condition that is life-threatening or can interfere with or be aggravated by the exercise training
- Uncontrolled Diabetes (HbA1c ≥8.0),
- Hypertensive Blood Pressure ≥160 mm Hg Systolic and/or 100 mm Hg Diastolic,
Relative (should consult a physician)
- Major risk factors for coronary heart disease
- Uncontrolled diabetes or musculoskeletal limitations