Article Title



M.C. Nelson, M.P. Casanova, J.R. Ball, R.D. Midence, C.A. Vella, FACSM

University of Idaho, Moscow, ID

Previous research has consistently demonstrated that a bout of uninterrupted sitting induces endothelial dysfunction in young, healthy men. However, there is little research examining the acute effects of uninterrupted sitting in other groups, especially women. PURPOSE: To investigate the effects of a single bout of uninterrupted sitting on hemodynamics in middle-aged and older men and women. METHODS: Thirty adults (14 men, 16 women; age, 46.6±8.8 y; body fat, 28.9±8.7%) performed a 3 h bout of uninterrupted sitting in a controlled laboratory environment. Body composition was assessed using multifrequency bioelectrical impedance analysis. Hemodynamic variables including blood pressure (BP), heart rate (HR), and calf circumference were measured at baseline, 1 h, 2 h, and 3 h of sitting. Additionally, superficial femoral artery (SFA) diameter and blood velocity were measured using Doppler ultrasound. SFA blood flow and shear rate were calculated using standard equations. Repeated measures ANOVA were utilized to understand changes in hemodynamic variables over time and between men and women. RESULTS: Systolic BP, diastolic BP, and calf circumference increased (p<0.01 for all), whereas HR decreased (p<0.001) over 3 h of sitting. SFA blood flow decreased over time with a quadratic trend (p<0.001; baseline: 76.1±47.9, 1 h: 46.2±28.8, 2 h: 39.0±19.7, 3 h: 34.7±18.5 mL/min). SFA arterial diameter did not change (p=0.12), however, SFA blood velocity decreased (p=0.03) over 3 h. Lastly, shear rate decreased over 3 h (p<0.001; baseline: 30.0±4.5, 1 h: 19.2±3.8, 2 h: 18.4±2.8, 3 h: 15.3±3.0 s-1). No differences were found between men and women for all variables. CONCLUSION: A single bout of uninterrupted sitting induced unfavorable changes in BP, calf circumference, and SFA blood flow, velocity, and shear rate in middle-aged and older men and women. Unfavorable changes in hemodynamic variables from repeated exposure to uninterrupted sitting throughout the lifespan may help explain the increased risk for cardiometabolic disease and premature mortality with excessive amounts of sedentary behavior.

Supported by: University of Idaho Webb Education Faculty Endowment and University of Idaho Exercise Physiology Research Laboratory.

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