Daniela Paz, Sasha Riley, Erik Hanson, FACSM. University of North Carolina Chapel Hill, Chapel Hill, NC.

BACKGROUND: It is well established that sedentary behavior (SB) increases the risk of cardiovascular disease (CVD), which is the leading cause of death annually. Acute bouts of prolonged sitting have been shown to increase arterial stiffness (AS) which is an independent risk factor for CVD. Currently, the use of sitting interruption strategies has produced mixed results. One option that has shown promising results in decreasing AS is an acute bout of aerobic exercise. However, it is unknown if aerobic exercise is a strong enough stimulus to attenuate increases in AS across a prolonged sitting bout. Therefore, the purpose of this study is to evaluate the effects of prolonged sitting with and without a prior bout of moderate-intensity aerobic exercise on brachial-femoral (bfPWV) pulse wave velocity and on femoral-ankle (faPWV) pulse wave velocity. METHODS: In the spring of 2022, 22 healthy, active adults (18-35 yrs) will be recruited. They will undergo a randomized crossover design with two experimental conditions, exercise (EX) and standing (STAND), preceded by a familiarization visit. Participants will report back to lab between 1-7 days after the familiarization visit for their first experimental visit and 2-7 days after that for their second experimental visit. For the experimental visit, participants will consume a protein bar two hours prior to the start of the visit to reduce hunger distractions. Participants will then undergo baseline measures of bfPWV and faPWV in a supine position followed by 30 minutes of brisk walking (X-Y% of heart rate reserve) followed by 5 minutes of standing (EX), or 35 minutes of standing (STAND) depending on the condition. Participants will then complete a 2-hour uninterrupted sitting bout. During this time the participant will sit quietly with their knees at a 90-degree angle while performing desk work. BfPWV and faPWV measures will be repeated pre- and post-sitting. The effects of prolonged sitting on AS with and without prior aerobic exercise will be analyzed using a linear mixed model. ANTICIPATED RESULTS: It is hypothesized that performing an acute aerobic exercise bout will attenuate the increases in brachial-femoral and femoral-ankle PWV over a prolonged sitting bout.

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