Effects of alternating standing and sitting compared to prolonged sitting on cerebrovascular hemodynamics
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Previous research suggests that prolonged sitting may acutely reduce cerebral blood flow velocity (CBFv). The purpose of this study was to evaluate the effects of alternating standing and sitting vs prolonged sitting on CBFv.
This randomized crossover study enrolled working adults (N = 25) with pre-to-stage 1 hypertension not using antihypertensive medications, and a body mass index (BMI) from 25 to < 40 kg/m2. Subjects participated in two simulated workday conditions: (1) sitting continuously (SIT), and (2) alternating standing and sitting every 30 min (SS). Beat-to-beat systolic, mean and diastolic CBFv were recorded bilaterally for 1 min via insonation of the middle cerebral artery using transcranial Doppler ultrasonography before (morning), between (midday) and following (afternoon) two 3-h 40 min work periods.
Mean ± SD age was 42 ± 12 years, blood pressure (BP) was 132 ± 9/83 ± 8 mmHg, and BMI was 32 ± 5 kg/m2. Cerebrovascular hemodynamics did not differ across condition (P > 0.05). There were, however, significant nonlinear effects of time (decrease from morning to midday; increase from midday to afternoon) on systolic CBFv (P = 0.014), mean CBFv (P = 0.001), diastolic CBFv (P = 0.002), and pulsatility index (P = 0.038). When overall time effects were evaluated during each time interval, mean and diastolic CBFv significantly decreased morning to midday and all CBFv increased from midday to afternoon. When separated by condition, significant time effects were observed for all CBFv during SIT (P < 0.02) but not SS (P > 0.05).
In individuals with elevated BP and BMI, CBFv significantly decreased by midday and increased by afternoon, especially during a workday of prolonged sitting. Future studies should evaluate the combination of frequent walks and a sit-stand desk to break up prolonged sitting.
KeywordsSedentary behaviour Sit-stand desk Cerebrovascular hemodynamics Transcranial Doppler
Cerebral blood flow velocity
Carotid-femoral pulse wave velocity
Carotid-radial pulse wave velocity
Diastolic blood pressure
Mean arterial pressure
Pulse wave velocity
Transcranial Doppler ultrasonography
The authors would like to thank Humanscale and the National Institutes of Health through Grant Number UL1TR000005 (University of Pittsburgh CTSI, providing research registry support) for their support. The authors would also like to thank University of Pittsburgh's K. Leroy Irvis Fellowship and the University of Kansas Alzheimer's Disease Center (P30 AG035982) for supporting Dr. Perdomo's time.
Compliance with ethical standards
Conflict of interest
Dr. Gibbs discloses funding from Humanscale. Drs. Perdomo, Kowalsky, Balzer and Mr. Taormina disclose no conflicts of interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Written informed consent was obtained from all participants.
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