Abstract
Prolonged sitting increases cardiovascular disease (CVD) risk, however the physiological mechanisms contributing to CVD from acute sitting exposure are not well-understood. Therefore, this study investigated the heart rate (HR) and variability (HRV) responses to prolonged sitting and after interrupting prolonged sitting (e.g., walking). Electronic databases were searched (inception-August 2020) for studies which exposed adults to prolonged (≥1 h) sitting with and/or without interruptions. Twenty-one articles (27 trials, n = 537) met inclusion criteria. Prolonged sitting non-significantly increased HR (weighted mean difference (WMD) = 0 bpm, 95% CI: −2, 3) and HRV (standardized mean difference (SMD) = 0.12, 95% CI: −0.08, 0.33) compared to pre-sitting baseline. Interrupting prolonged sitting yielded a non-significant small increase in HR (WMD = 4 bpm, 95% CI: 0, 7) compared to pre-sitting baseline. Sub-group analyses investigating interrupting prolonged sitting revealed small-to-moderate increases in HR in healthy populations (WMD = 6 bpm, 95% CI: 1, 10) and following walking interruptions (WMD = 7 bpm, 95% CI: 3, 11). In conclusion, prolonged sitting does not significantly affect HR or HRV. However, interrupting prolonged sitting yielded a small non-significant increase in HR, potentially indicative of increased metabolic demand. Further research is needed to investigate poor CVD outcomes via autonomic disruption from prolonged sitting.
Highlights
Regular sedentary behavior exposure, defined as low energy expenditure (≤1.5 metabolic equivalents) in a seated, reclined, or lying posture (Tremblay et al, 2017), is associated with increased cardiovascular disease (CVD) incidence and mortality (Biswas et al, 2015)
Prolonged Sitting and Heart Rate Variability where prolonged sitting causes blood pooling in the lower extremities (Dempsey et al, 2018), leading to reduced venous return, decreased stroke volume, and a subsequent decrease in lower extremity blood flow (Thosar et al, 2012; De Brito et al, 2015; Credeur et al, 2019)
Reduced heart rate variability (HRV) at rest is indicative of autonomic dysfunction, a known risk factor of CVD (Ebara et al, 2008), research evaluating the effects of prolonged sitting exposure on cardioautonomic function is limited and inconsistent in both findings and methodology
Summary
Regular sedentary behavior exposure, defined as low energy expenditure (≤1.5 metabolic equivalents) in a seated, reclined, or lying posture (Tremblay et al, 2017), is associated with increased cardiovascular disease (CVD) incidence and mortality (Biswas et al, 2015). A recent metaanalysis (Paterson et al, 2020) reported that exposure to uninterrupted prolonged sitting leads to acute lower-extremity endothelial dysfunction, perhaps indicating a direct hemodynamic effect on the lower extremity vasculature These effects may result from systemic cardiovascular effects. The decrease in stroke volume can unload the baroreceptors, triggering the autonomic nervous system to increase heart rate (HR) in an attempt to maintain cardiac output while vasoconstricting resistance vessels to maintain blood pressure (Shaffer et al, 2014). Overtime, this may result in an elevated resting heart rate, which is associated with CVD risk (Altenburg et al, 2019). Reduced heart rate variability (HRV) at rest is indicative of autonomic dysfunction, a known risk factor of CVD (Ebara et al, 2008), research evaluating the effects of prolonged sitting exposure on cardioautonomic function is limited and inconsistent in both findings and methodology (sitting duration, sitting control, measurement devices, etc.)
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