Sedentary time (ST) has recently been included in the 24-h activity guidelines. However, the impact of habitual sedentary patterns on autonomic cardiovascular regulation are unclear. We tested the hypothesis that more ST and fewer sedentary breaks were associated with lower cardiovagal baroreflex sensitivity. More frequent sedentary breaks, but not total ST, was independently and positively associated with vagally-mediated blood pressure control. Breaking up ST could be more important than total ST for cardiovascular health. Novelty: Breaks in sedentary time is an independent predictor of cardiovagal baroreflex sensitivity, with more frequent breaks associated with better vagally-mediated blood pressure regulation.

Introduction: Acute, laboratory-based bouts of prolonged sitting attenuate lower-limb arterial endothelial-dependent vasodilation. However, the impact of habitual sedentary patterns on popliteal artery endothelial health is unclear. We tested the hypothesis that greater habitual total sedentary time, more time spent in prolonged sedentary bouts, and fewer sedentary breaks would be associated with worse popliteal flow-mediated dilation (FMD) responses. Methods: This cross-sectional study used 98 healthy participants (19–77 years, 53 females) that wore an activPAL monitor on the thigh for 6.4 ± 0.8 days to objectively measure sedentary activity and completed a popliteal ultrasound assessment to determine FMD. Both relative (%baseline diameter) and absolute (mm) FMD were calculated. Using bivariate correlation and multiple regression analyses, we examined if there were relationships between sedentary outcomes and FMD while statistically controlling for any potential confounders. Results: In the multiple regression model, age ( p = 0.006, β = −0.030, 95% CI = −0.051, −0.009) and total time in sedentary bouts > 1 hour ( p = 0.031, β = −0.005, 95% CI = −0.009, −0.001) were independent predictors of relative FMD. Age (β = −0.002, 95% CI = −0.003, −0.001), mean blood flow (β = 0.013, 95% CI = 0.002, 0.024), moderate-intensity physical activity (β = 155.9E−5, 95% CI = 22.4E−5, 289.4E−5), sedentary breaks (β = 0.036, 95% CI = 0.007, 0.066), and total time spent in sedentary bouts > 1 hour (β = −25.02E−5, 95% CI = −47.67E−5, −2.378E−5) were predictors of absolute FMD (all, p < 0.047). All independent outcomes remained significant after partially controlling for all other predictor variables (all, p < 0.031). Conclusions: Habitual prolonged sedentary bouts and sedentary breaks, but not total sedentary time, were predictors of popliteal endothelial-dependent vasodilatory function. The patterns by which sedentary time is accumulated may be more important than the total sedentary time on lower-limb arterial health.

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The physical fitness of Canadian adults has decreased over the past 30 years, while sedentary time has increased. However, it is unknown if university students studying human movement exhibit similar population declines. Physical fitness (i.e., anthropometrics, musculoskeletal fitness, and aerobic fitness) and habitual activity (e.g., physical activity, stationary time, etc.) was measured in a cohort of kinesiology students (Post30; 2010–2016; n = 129 males, 224 females) using standardized fitness testing and accelerometry, respectively. Physical fitness was compared to data collected on a cohort of students from the same institution and program, 30 years prior (i.e., Pre, 1984–1987, n = 103 males, 73 females). Post30 had greater waist circumference (males: 83.6 ± 9.1 cm vs. 77.8 ± 8.3 cm, females: 77.1 ± 9.7 cm vs. 70.3 ± 5.2 cm, both p < 0.001) and lower estimated maximal aerobic fitness (males: 55 ± 11 vs. 63 ± 7, females: 45 ± 10 vs. 50 ± 7 mLO2/kg/min, both, p < 0.001). Compared to Pre, male Post30 vertical jump (53.6 ± 10.2 vs. 57.0 ± 8.4 cm, p = 0.04) and female Post30 broad jump (178.7 ± 22.1 vs. 186.0 ± 15.5 cm, p < 0.001) were lower. A subsample (n = 65) of Post30 whose habitual activity was assessed, met the aerobic portion of Canadian physical activity guidelines (~400 min/week), but spent excessive amounts of time stationary (10.7 h/day). Current kinesiology students may not be immune to population decreases in physical fitness. Relative to previous group of students interested in movement, fitness was lower in our sample, potentially attributed to excessive stationary time. Regular assessment of physical fitness in kinesiology curriculums may be valuable to understand these declining trends in undergraduate students that mimic population declines in fitness.