Introduction 

Compared to other non-communicable diseases, cardiovascular diseases (CVD) are the main cause of death and have the highest economic impact in the United States (US). Promoting participation in moderate-to-vigorous intensity physical activity (MVPA), which lowers the risk of CVD in a dose-response manner, is one well-known primary prevention method. However, just one-third of US individuals between the ages of 18 and 64 adhere to the current physical activity recommendations, which call for sedentary habits such as spending time in a supine position (SB). Given that the typical US adult self-reports sitting for more than four hours per day (6.4 hours), this particular aspect of SB is probably highly controllable. 

Unfortunately, despite the fact that SBs are much more common and biologically different from physical activity in terms of CVD risk, there is much less study on these behaviors. Although international recommendations recommend that people reduce the amount of time they spend sitting down and replace it with physical exercise, such general public health messages are unlikely to have a significant impact on behavior change at the population level. Public health messages about the ideal method for SB interruption are therefore required. There are currently three issues that need to be addressed in order to create effective SB substitution policies: I a lack of mechanistic data to establish a biologically plausible link between SB and adverse cardiovascular responses; (ii) an unknown optimal dose of SB replacement to mitigate adverse cardiovascular responses; and (iii) a lack of knowledge about the practicality and important behavioral factors involved. The clinical trial Sitting with Interruption and Whole-Body Cardiovascular Health (SWITCH), which tries to close each of the aforementioned gaps in SB policy creation, is described in this manuscript’s protocol for part I. 

By contrasting the arterial stiffness (AS) responses to three realistic SB substitution strategies vs. uninterrupted SB in middle-aged adults, Part I of SWITCH will establish biological plausibility and identify a mechanism-informed SB substitution strategy to reduce the risk of CVD (36 to 55 years old). In this section, a mechanistic conceptual model of the association between SB and CVD risk will be put to the test (Fig. 1).

According to the researchers, endothelial dysfunction results from acute sitting-related increases in AS of 0.2–0.4 m/s as measured by carotid–femoral pulse wave velocity (PWV), which are exacerbated by a number of harmful autonomic, hormonal, and metabolic factors. Hemodynamic changes are what initially cause endothelial dysfunction. In spite of known risk factors, these acute shocks enhance CVD risk, chronically elevated AS, and longer-term structural alterations. Focus groups will also be used in Part I to assess the socioecological factors that influence SB and to aid in the creation and improvement of a socioecological model for SB reduction. The identification of a physiologically plausible connection between cause and effect was a crucial criterion for policy formation employed by public health organizations, and it inspired the design of our study (i.e., understanding the mechanisms by which prolonged sitting leads to increased CVD risk). 

Cardiovascular Health (SWITCH) will find recommendations for SB replacement that are socioecologically grounded and informed by mechanisms to reduce the risk of CVD. Part I of SWITCH includes both a qualitative and a quantitative research component to help achieve this goal. 

Goal of this study 

The objective of the study’s quantitative component is to examine the AS responses to three practical SB substitution procedures in a factorial, randomized cross-over trial. These substitution techniques include walking, 5 minutes of light physical activity (LPA), once per hour; standing, 15 minutes of stillness, once per hour; or combining the two with an interruption rate of twice per hour. The researchers believe that replacing SB once per hour with either 15 minutes of standing or 5 minutes of LPA will prevent acute elevations in AS. However, they concede that this frequency of interruption is less likely to be followed in a naturalistic context. The researchers also believe that the combined, more frequent breaks will avoid acute rises in AS to a larger degree than either other technique alone. 

Methods 

For this randomized crossover trial, healthy men and women (n = 56, ages 36 to 55) who are sedentary (sitting for more than 8 hours per day) and inactive (90 minutes per week of moderate-to-vigorous level physical activities) will be recruited. Participants will complete the following four 4-hour conditions: I SB with once-per-hour breaks of 5 minutes to walk; (ii) SB with once-per-hour breaks of 15 minutes to stand; (iii) SB with twice-per-hour breaks of 5 minutes to walk and 15 minutes to stand; and (iv) SB with no breaks (i.e., control). We will improve our socioecological SB reduction approach through focus groups. 

Two days previous to each experimental visit, sedentary behavior will be evaluated using thigh-worn accelerometry/posture monitoring (MOX1, Maastricht Instruments).

Fig. 3 The quantitative research component’s timetable. Including (A) a flowchart outlining the steps and visit duration, and (B) the timing of the measurements and interruptions of sedentary behavior over the course of the 4-hour sedentary behavior conditions. 

Results 

The main result will be the difference in aortic arterial stiffness between each substitution method and the control (SB with no breaks), measured as pulse wave velocity (PWV, m/s). The findings of this study will make it easier to create a future randomized controlled trial to evaluate a workable, mechanism-informed SB-reduction strategy and assist in the creation of SB policy. 

Related products 

MOX1 Activity logger for physical activity assessment.  

The MOX1 is a validated accelerometer-based activity logger that seamlessly measures and records high resolution raw acceleration data up to 7 days. By using the IDEEQ software featuring our proprietary algorithms, objective measurements of human physical activity can be classified and quantified. The waterproof system design and biocompatible adhesive ensures easy application and comfortable wear by the subject.  

How can we help you with your research?   

Maastricht Instruments creates equipment in the field for accelerometry. We provide support for Clinical research, E-health applications, accelerometry algorithms and data processing and analyses. Consult us about our accelerometry products, MOX1, MOX2, MOX3, MOX5 and BACE. or eHealth applications: Hospital Fit and Miss Activity  

Reference 

Higgins S, Cowley ES, Paterson C, Hanson ED, Dave GJ, Meyer ML, Lin FC, Gibbs BB, Vu M, Stoner L. Protocol for a study on sitting with interruption and whole-body cardiovascular health (SWITCH) in middle-aged adults. Contemp Clin Trials. 2022 Dec 9;125:107048. doi: 10.1016/j.cct.2022.107048. Epub ahead of print. PMID: 36509249.