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Purpose 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. Methods 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/m 2 . 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. Results Mean ± SD age was 42 ± 12 years, blood pressure (BP) was 132 ± 9/83 ± 8 mmHg, and BMI was 32 ± 5 kg/m 2 . 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). Conclusions 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.

ObjectiveThe Stand Back study evaluated the feasibility and effects of a multicomponent intervention targeting reduced prolonged sitting and pain self-management in desk workers with chronic low back pain (LBP).MethodsThis randomised controlled trial recruited 27 individuals with chronic LBP, Oswestry Disability Index (ODI) >10% and desk jobs (sitting ≥20 hours/week). Participants were randomised within strata of ODI (>10%–<20%, ≥20%) to receive bimonthly behavioural counselling (in-person and telephone), a sit-stand desk attachment, a wrist-worn activity-prompting device and cognitive behavioural therapy for LBP self-management or control. Self-reported work sitting time, visual analogue scales (VAS) for LBP and the ODI were assessed by monthly, online questionnaires and compared across intervention groups using linear mixed models.ResultsBaseline mean (SD) age was 52 (11) years, 78% were women, and ODI was 24.1 (10.5)%. Across the 6-month follow-up in models adjusted for baseline value, work sitting time was 1.5 hour/day (P<0.001) lower comparing intervention to controls. Also across follow-up, ODI was on average 8 points lower in intervention versus control (P=0.001). At 6 months, the relative decrease in ODI from baseline was 50% in intervention and 14% in control (P=0.042). LBP from VAS was not significantly reduced in intervention versus control, though small-to-moderate effect sizes favouring the intervention were observed (Cohen’s d ranged from 0.22 to 0.42).ConclusionAn intervention coupling behavioural counselling targeting reduced sedentary behaviour and pain self-management is a translatable treatment strategy that shows promise for treating chronic LBP in desk-bound employees.Trial registration number NCT0224687; Pre-results.

We evaluated the effects of a simulated workday of prolonged sitting on blood pressure (BP) and pulse wave velocity (PWV) and examined whether posture (seated vs. supine) affected responses. Participants (n = 25) were adults, with overweight/obesity and elevated BP, and performed seated desk work for 7.5 h. BP and PWV were measured in seated and supine postures at baseline (7:15 a.m.), midday (12:05 p.m.), and afternoon (4:45 p.m.). Generalized linear mixed models evaluated the effects of prolonged sitting on BP and PWV within each posture and interactions by posture and sex. In the recommended postures, seated BP and supine carotid-femoral pulse wave velocity (cfPWV) and carotid-ankle pulse wave velocity (caPWV), but not carotid-radial pulse wave velocity (crPWV), significantly increased over the simulated seated workday (all p < 0.05; effect sizes [d] ranged from 0.25 to 0.44). Whilst no posture-by-time interactions were observed (p > 0.05), BP, caPWV, and crPWV were higher when seated versus supine (main effects of posture p < 0.05; d ranged from 0.30 to 1.04). Exploratory analysis revealed that females had greater seated BP responses (p for interaction <0.05); seated PWV and supine BP and PWV responses were similar by sex (p for interaction >0.05). A simulated workday of prolonged sitting increased seated BP and supine cfPWV and caPWV, and posture minimally influenced these responses. These results add to the evidence suggesting a deleterious effect of prolonged sitting on cardiovascular health.

Cerebral autoregulation in healthy humans was studied using a novel methodology adapted from Bendat nonlinear analysis technique. A computer simulation of a high-pass filter in parallel with a cubic nonlinearity followed by a low-pass filter was analyzed. A linear system transfer function analysis showed an incorrect estimate of the gain, cut-off frequency, and phase of the high-pass filter. By contrast, using our nonlinear systems identification, yielded the correct gain, cut-off frequency, and phase of the linear system, and accurately quantified the nonlinear system and following low-pass filter. Adding the nonlinear and linear coherence function indicated a complete description of the system. Cerebral blood flow velocity and arterial pressure were measured in six data sets. Application of the linear and nonlinear systems identification techniques to the data showed a high-pass filter, like the linear transfer function, but the gain was smaller. The phase was similar between the two techniques. The linear coherence was low for frequencies below 0.1 Hz but improved by including a nonlinear term. The linear + nonlinear coherence was approximately 0.9 across the frequency bandwidth, indicating an improved description over the linear system analysis of the cerebral autoregulation system.

Purpose It is important to understand acute dose-response relationships on cardiovascular health and brain health. Thus, we evaluated the acute effects of 10- and 30-min exercise bout on blood pressure (BP), pulse wave velocity (PWV) and cerebral blood flow velocity (CBFv). Methods Fifteen adults (mean age 45.4 ± 8.9 years, 87% female) participated in this randomized crossover study comprised of three acute experimental sessions: a 10-min exercise bout (EX10), a 30-min exercise bout (EX30) and a sitting control (SIT). Exercise consisted of walking on a treadmill at 70–75% of age-predicted maximum heart rate. BP, PWV and CBFv were measured 30 and 60 min after each experimental session. BP was obtained at the brachial artery while PWV was measured at the carotid-femoral and carotid-radial sites. CBFv was measured at the middle cerebral artery using a 2 MHz transcranial Doppler. Results Compared to SIT, BP was lower following EX10, and even lower following EX30 ( P  < 0.05). Though EX30 and SIT resulted in similar PWV responses ( P  > 0.05), EX10 resulted in a higher carotid-femoral PWV vs. EX30 and SIT at 30 min (both P  = 0.02) and a lower carotid-radial PWV vs. SIT at 60 min ( P  = 0.004). CBFv did not differ across conditions (all P  > 0.05). Conclusions Our results suggest that 10- and 30-min aerobic exercise bouts have differential effects on BP and PWV. CBFv did not change in the hour following either bout. Further research is needed to elucidate the mechanisms and effects of 10- vs 30-min bouts of exercise.

Arterial stiffness, often measured by carotid-femoral pulse wave velocity (cfPWV), is a subclinical marker of cardiovascular disease that is known to be reduced by exercise training. Exercise is also known to have acute vascular effects, yet it is unclear whether exercise 24 h before cfPWV testing influences this outcome. Thirty healthy, young adults completed a supervised, 30-min bout of moderate-to-vigorous intensity treadmill running. cfPWV, systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) were measured both before (after 48 h of abstaining from exercise) and 24 h after (with no additional exercise) the exercise session. From pre-exercise to 24 h post exercise, cfPWV decreased from 6.05±0.82 to 5.84±0.87 m s(-1) (P=0.02), SBP from 119.7±13.8 to 116.8±11.4 mm Hg (P=0.03) and DBP from 65.1±5.7 to 63.2±5.4 mm Hg (P=0.02), with no significant changes in HR. cfPWV was positively correlated with SBP pre-exercise (r=0.54, P<0.01) and post exercise (r=0.53, P<0.01). Changes in blood pressure explained 4-5% of the variability in cfPWV change; adjustments slightly attenuated the 24-h effects of exercise on cfPWV. Some evidence of gender differences was observed with higher cfPWV in males across assessments (P<0.05) and statistically significant reductions in cfPWV in males (-0.36±0.54 m s(-1) (P=0.02)) but not in females (-0.07±0.31 m s(-1) (P=0.41)). In conclusion, cfPWV decreased 24 h after an exercise bout, suggesting that exercise completed in the past 24 h should be considered before cfPWV testing.

We evaluated the effects of a simulated workday of prolonged sitting on blood pressure (BP) and pulse wave velocity (PWV) and examined whether posture (seated vs. supine) affected responses. Participants (n=25) were adults, with overweight/obesity and elevated BP, and performed seated deskwork for 7.5 hours. BP and PWV were measured in seated and supine postures at baseline (7:15AM), mid-day (12:05PM), and afternoon (4:45PM). Generalized linear mixed models evaluated the effects of prolonged sitting on BP and PWV within each posture and interactions by posture and sex. In the recommended postures, seated BP and supine cfPWV and caPWV, but not crPWV, significantly increased over the simulated seated workday (all p<0.05; effect sizes (d) ranged from 0.25–0.44). Whilst no posture-by-time interactions were observed (p>0.05), BP, caPWV and crPWV were higher when seated vs. supine (main effects of posture p<0.05; d ranged from 0.30–1.04). Exploratory analysis revealed that females had greater seated BP responses (p-for-interaction<0.05); seated PWV and supine BP and PWV responses were similar by sex (p-for-interaction>0.05). A simulated workday of prolonged sitting increased seated BP and supine cfPWV and caPWV, and posture minimally influenced these responses. These results add to the evidence suggesting a deleterious effect of prolonged sitting on cardiovascular health.