Being sedentary at work, such as sitting in front of a work computer, led to lower blood pressure than standing for long periods. The findings are from a new study that also found that prolonged standing at work can be harmful to the heart and circulation.
Because physical activity has been found to lower blood pressure (BP), medical advice has always been to be more active and reduce time spent engaged in a sedentary lifestyle. Activities that don’t increase energy expenditure substantially above the resting level fall into the sedentary category, and that includes sitting at work.
While the benefits of physical activity on BP are well-known, what’s not is whether the place where the activity is done makes a difference. New research by the University of Turku in Finland compared sedentary behavior to physical activity in specific domains – at work, during leisure time, and on non-work days – to see how each one affected BP over 24 hours.
A continuous, 24-hour measurement shows how BP changes over the day and during sleep, providing a more accurate overall picture of a person’s BP.
“Rather than any single measurement, 24-hour blood pressure is a better indication of how blood pressure stresses the heart and blood vessels throughout the day and night,” said doctoral researcher Jooa Norha, the study’s lead author. “If blood pressure is slightly high throughout the day and does not fall sufficiently even at night, blood vessels start to stiffen and the heart has to work harder to cope with the increased pressure. Over the years, this can lead to the development of cardiovascular disease.”
In the present study, 156 participants with an average age of 62 wore an accelerometer on their thighs to measure physical activity during work hours, leisure time, and days off from work. The activity was categorized into four types: sedentary (including lying and sitting), standing, light physical activity (including slow walking and moving) and moderate-to-vigorous physical activity (including fast walking, running, cycling, and stair climbing). The participants’ BP was measured automatically every half-hour for 24 hours. Measurements of interest to the researchers were mean 24-hour BP, daytime (that is, while awake), nighttime (asleep), systolic and diastolic BP, and the percentage of BP dipping that occurred at nighttime.
They found that sedentary behavior during work time was associated with a lower 24-hour diastolic BP. Here’s a simple explainer: diastolic BP is the second or ‘bottom’ number (e.g., the 80 in 120/80). It represents the pressure in the arteries during the heart’s resting phase, between beats. Because the heart muscle relaxes during diastole, that’s when the heart itself receives the majority of its blood flow. The researchers also found that spending more time standing at work was associated with a higher 24-hour diastolic BP, driven mostly by daytime diastolic BP. Non-workday standing was not associated with any BP variables.
“Standing leads to blood pooling in the lower extremities, which in turn leads to lower central blood volume which is compensated for by increased sympathetic activity (e.g., increased cardiac output and vascular tone),” the researchers explained.
What they mean is that standing for long periods can actually raise blood pressure, because the heart has to work harder to move the blood that has pooled in the lower limbs.
“A standing desk can provide a nice change from sitting at the office, but too much standing can be harmful,” Norha said. “It’s a good idea to take a break from standing during the work day, either by walking every half an hour or sitting for some parts of the day.”
The findings suggest that being sedentary while at work is not necessarily bad for BP. Nonetheless, the researchers stress the importance of engaging in physical activity during leisure time and outside of the work environment.
“It is good to remember that being physically active at work is not enough on its own,” said Norha. “Engaging in diverse physical exercise during leisure time helps to maintain fitness, making work-related strain more manageable. Similarly, employees with predominantly sedentary jobs should ensure that they get enough exercise during their leisure time.”
The research findings are somewhat paradoxical. A future, large-scale study would determine if they can be replicated.
The study was published in the journal Medicine & Science in Sports & Exercise.
Source: University of Turku
