Long COVID-19 is defined as signs, symptoms and conditions that develop after initial SARS-CoV-2 infection and persist for over four weeks. Nearly 2 million people in the UK are currently experiencing self-reported long COVID, of which 61% of these people have been living with symptoms for more than a year. (Office for National Statistics, 2023).
Long COVID presents with over fifty different symptoms, which can vary significantly from person to person. People with long COVID demonstrate significantly greater levels of sedentary behaviour (Delbressine et al., 2021), partially explained by fatigue being one of the most common symptoms. Sedentary time is known to have an adverse effect on vascular function and can increase the risk of cardiovascular disease. Acute sitting periods as short as one hour can worsen vascular function (Taylor et al., 2022), however, interrupting these periods with short bouts of movement has been shown to mitigate the negative effect on vascular health (Paterson et al., 2020). Arterial stiffness is a measure of vascular dysfunction through changes in the structure and function of blood vessels. Carotid-femoral pulse wave velocity (cfPWV) is the gold standard tool to non-invasively measure arterial stiffness.
This study aimed to investigate whether prolonged sitting for 2 hours induces a vascular response in people with long COVID and if interrupting sitting periods has a beneficial effect on arterial stiffness. Participants were tasked with sitting still for two hours. Interruption includes three bouts of five sit-to-stands, five calf raises, and three minutes of self-paced walking to mimic activities of daily living. Measures of central and peripheral blood pressure, arterial stiffness (SphygmCor XCEL), executive function (TrailMaking Tasks), and cerebral oxygenation (Near Infrared Spectroscopy) were recorded at baseline and following two hours of interrupted or uninterrupted sitting. Ethical approval was obtained by Health and Care Research Wales (IRAS: 309606 22/SC/0120).
Thirty participants (52.84  13.19 years, symptoms lasting >12 months) completed both experimental visits and were used in the analysis. Repeated measures ANOVA demonstrated a significant increase in central systolic blood pressure (cSBP) (P=0.005, ηp2 = 0.258), central diastolic blood pressure (cDBP) (P<0.001, ηp2 = 0.519), brachial systolic blood pressure (SBP) (P<0.001, ηp2 = 0.348) and mean arterial pressure (MAP) (P<0.001, ηp2 = 0.391) following prolonged sitting regardless of interruptions. There was no significant change in cfPWV (P=0.541). Mental fatigue significantly increased in both conditions (P=0.019, ηp2 = 0.194).
This research demonstrates that sitting for 2 hours instigates changes in central and peripheral blood pressure, which is thought to be driven by blood pooling in the lower limbs resulting in a decrease in venous return and cardiac output causing compensations through the sympathetic nervous system including increased peripheral vascular resistance (Adams et al., 2023). Although interrupting sitting did not affect cfPWV, it is unclear whether the intensity of interruption or the duration of sitting time was sufficient to induce changes in arterial stiffness. Additionally, understanding the effect of chronic periods of sedentary behaviour through prolonged sitting on arterial stiffness is important to understand the clinical relevance of increased sedentary behaviour in long COVID.