Breaking up Prolonged Sedentary Behavior to Improve Cardiometabolic Health

The purpose of this Phase 1 research study is to answer two questions: (1) How frequent should periods of prolonged sedentary time be interrupted? and (2) What is the appropriate duration or length of time of these breaks in sedentary time? To address these questions, this project will conduct a state-of-the-art adaptive dose finding study under controlled laboratory conditions to determine the minimally effective dose (the smallest dose) that yields cardiometabolic benefit for two separate sedentary break elements (frequency and duration). Study findings will ultimately determine how often and for how long people should break up periods of prolonged sedentary time to transiently improve established cardiovascular risk factors; key foundational information critical to the success of future long-term trials and ultimately public health guidelines. Primary Aim: To determine the minimally effective dose combination(s) of frequency and duration needed to provide cardiometabolic benefit during an 8-hour experimentation period. Specifically, the study will determine: 1a. For each fixed duration, the minimum sedentary break frequency (e.g., every 30 min, 60 min, 120 min) that demonstrates a reduction in systolic BP, diastolic BP, or glucose compared with a sedentary control condition. 1b. For each fixed frequency, the minimum sedentary break duration (e.g., activity breaks of 1 min, 5 min, 10 min) that demonstrates a reduction in systolic BP, diastolic BP, or glucose compared with a sedentary control. Secondary Aim: It is also critical to public health strategy to assess the acceptability/feasibility of various sedentary break doses as too high a dose will yield poor uptake. To address this need, the maximally tolerated dose (the highest dose that does not cause undue physical/psychological distress) for frequency and duration of sedentary breaks will also be determined via assessment of 4 constructs: physical exhaustion/fatigue, affect (e.g., mood, emotion), tolerability (e.g., completion of dose protocol), and safety (e.g., hypoglycemia). Maximally tolerated dose will be defined as the highest dose where \<20% of participants exhibit an adverse outcome.