Can sitting for just 3 hours non-stop at one time hurt the heart?
Prolonged sitting has been demonstrated to have a negative effect on peripheral arteries’ vasodilation in previous studies. But there has not been enough research done on vasoconstrictor function (which could help us analyze total vasoreactivity), nor on central vascular behavior after a period of prolonged sitting. Even though we already know that continuous long-term, uninterrupted sitting bouts have a negative impact on the heart, this cohort study set out to identify what just one bout of prolonged sitting itself could do to the central cardiovascular function as well as the peripheral vascular function. The prolonged sitting period was for 3 hours at one time; a pre-, during, and post-design was used, and only relatively healthy adults were tested.
The study included 20 participants who were between 18-55 years old; 13 males and 7 females; asymptomatic (“i.e., resting blood pressure < 140/90, and no signs of arrhythmias”); without cardiovascular, metabolic or neurological diseases; not pregnant; and not smokers. Before each five-hour experiment, patients had fasted for two hours, had no caffeine for 12 hours, and no alcohol nor strenuous physical activity for twenty-four hours. The volunteer subjects filled medical health history forms, then laid down for 15 minutes while their baseline measurements were taken. Then the volunteers sat in a chair for three hours straight. Participants were not allowed to listen to heavy music and they were not to move their legs, but they could move their upper body. They were observed by two research assistants to make sure the participants were adhering to the study’s protocol. ECG, pulse wave analysis, and shear rate were performed for cardiovascular measures, and they were repeated for every hour that the participants were sitting. Then, after the three hours of sitting, the individuals were laid down for post-sitting measurements. After the experiment, the volunteers were each given a triaxial accelerometer to wear for a week, to test their physical activity status.
Aortic pulse wave velocity (aPWV) was not measured in 3 volunteers due to “limitations in cuff size (i.e., limb circumference exceeded optimal range of cuff for an accurate measurement).” Artery images were taken. Blood velocity signals were recorded. Videos were taken during cuff occlusion and release. There was venous pooling in the calf during the process of sitting, according to a tape measure. LabChart software interpreted heart rate (HR) and R-R variability (HRV). Physical activity status was based off the Freedson 1998 cut points. These cut points are 2,020 and 5,999 counts, consistent with NHANES physical activity data reduction. To analyze the prolonged sitting (10 to 180 minutes) on central cardiovascular function, the study used one-way repeated measures ANOVAs, with Bonferroni as the post-hoc test.
During pre/post-sitting time points, MAP showed no alteration (p > 0.05) except a great decrease in resting HR, AP, and AIx (p < 0.05). aPWV was moderately increased (p = 0.009). It was also demonstrated that males (as opposed to females) had an increase in aortic stiffening after a bout of prolonged sitting. Also, physical status did not affect central hemodynamics or vascular function after the period of prolonged sitting (p > 0.05).
Although there was a decrease in LF, there was “no change noted for HF (p = 0.115, d = 0.4), LF/HF ratio (p = 0.145, d = 0.33) and total power (p = 0.18, d = 0.37),” according to the study. The posterior tibial arteries also reduced in size during and after the period of long-term sitting. The velocity of blood during reactive hyperemia after the sitting intervention decreased as well (p < 0.05). And, after sitting for 180 minutes, there was a slight increase in calf circumference (p <0.001).
Prolonged sitting has been shown to affect central hemodynamics in this study (aPWV increased, and Aix decreased). There was less reactivity in the legs’ veins and aortic vascular stiffening. Therefore, this study shows that, even in relatively healthy adults, just one 3-hour period of uninterrupted sitting can negatively affect peripheral and central vascular health. The study population was very small (20 participants), which may have weakened the study and did not allow certain parameters to be tested accurately (such as race/ethnicity and gender impact). More studies may be needed, but the results of this one should definitely contribute to patient counseling on the hypothesis of negative impacts in 3 hours of prolonged sitting in relatively healthy adults. “A single bout of prolonged, uninterrupted sitting may serve as a precursor for initiating the deleterious cardiovascular health response associated with long-term sedentarism.”
- Studies had shown previously that an accumulation of long bouts of sitting can lead to a decrease in both central and peripheral venous function. This study focused more in depth on vasoconstrictor function and the effects of just one single 3-hour period of uninterrupted sitting.
- Results demonstrated that even one bout of prolonged sitting can in fact negatively impact both peripheral and central venous function and stiffening in relatively healthy adults.
- There were only 20 volunteers studied; more subjects will be needed for confirmation, but many results were statistically significant, and we can apply the findings to our practices to prevent more cardiovascular conditions.
Credeur, Daniel P; Dolbow, David R; Fryer, Simon M; Jones, Raymond; McCoy, Stephanie M; Sabina M. Miller; Stone, Keeron; Stoner, Lee. “Impact of Prolonged Sitting on Peripheral and Central Vascular Health.” The American Journal of Cardiology. 2018. https://www.ncbi.nlm.nih.gov/pubmed/30409414. 13 January 2019.
Annahita Forghan, Pharm.D. Candidate 2019, LECOM College of Pharmacy