Sitting Interruption and Whole-body Cardiovascular Health

Sedentary behaviors (SB) are biologically distinct but understudied heart disease risk factors. National and international agencies have concluded that the level of evidence for an overall and dose-response association between SB and heart disease mortality is moderate-strong. These agencies do not provide specific recommendations for breaking-up SB, though do call on the research community to facilitate policy development by establishing biological plausibility, identifying the optimal dose for SB substitution strategies, and conducting randomized clinical trials to test the efficacy of these strategies. Accordingly, the goal of this study is to identify mechanism-informed, socioecological-based SB substitution recommendations to reduce heart disease risk. To achieve this goal, two aims will be addressed. Aim 1 will identify a feasible SB substitution strategy to prevent the negative cardiovascular responses to prolonged SB (i.e., strategies that people will actually follow). Adverse cardiovascular responses to prolonged SB will be measured using aortic arterial stiffness (AS), a noninvasive test that predicts future heart disease. To accomplish this aim, 56 middle-aged (30-60 years) participants will provide written informed consent, prior to the measurement of aortic AS and associated mechanistic responses to the following over 4 hours, in a randomized crossover manner: (i) SB with a 5-minute walk break once per hour; (ii) SB with a 15-minute standing break once per hour; (iii) SB with two breaks per hour, alternating between a 5-minute walk and a 15-minute stand; and (iv) SB with no breaks (control). These strategies were selected based on extensive prior work by the investigators, and because they are feasible, which is a key component of this study. SB reduction strategies will only decrease heart disease risk if people are willing to adhere to future SB substitution recommendations. To increase the likelihood of feasibility and long-term adherence, Aim 2 will evaluate the determinants of SB using a socioecological model. This recognizes that behavior change is likely to be limited if the physical and sociocultural environments do not support the behavior change. To accomplish Aim 2, a combined inductive-deductive qualitative approach will be used. Participants who complete Aim 1 will participate in one of 6 focus groups (6-8 participants/group). Crucially, the outcomes from this proposal will be instrumental in helping to design a subsequent clinical trial to test a mechanism-informed yet feasible SB reduction intervention, and in doing so directly support the development of SB policy.

Inclusion criteria

• Aged between 30-60 years
• Insufficiently active: self-reported exercise <90 minutes per week for the past 3 months
• Sedentary: self-reported sitting >8 hours per day
• Self-reported ability to walk 4 blocks and climb 2 flights of stairs
• Possession of cellular phone able to receive text messages

Exclusion criteria

• Use of assisted-walking devices
• Comorbid condition that would limit the ability to reduce sedentary behavior (e.g., musculoskeletal condition, current chemotherapy)
• Plans for major surgery within next 3 months
• Recent history (<1 year) of ischemic heart disease, chronic heart failure, stroke, or chronic kidney disease
• Recent (< 1 year) or planned bariatric surgery
• Systolic blood pressure ≥160 mmHg or diastolic blood pressure ≥100 mmHg
• Current or recent (within last 6 months) pregnancy; current or recent (within last 3 months) breastfeeding
• Morbidly obesity (BMI >40 kg/m^2) or underweight (BMI <18.5 kg/m^2)
• Use of anti-hypertensive drugs
• Use of glucose-controlling medication
• Heavy alcohol consumption (>15 drinks per week)