New evidence sheds light on ways to prevent health damage from sitting 04/26/2018
Most of us fall prey to one health fad or another — until we tire of them or they're proven bogus.
We’ve seen the cabbage soup diet, the fat-free craze, Richard Simmons’ Sweatin’ to the Oldies, and who could forget the ThighMaster?
One of the hottest office trends is the standing desk — an attempt to counter the proven dangers of prolonged sitting.
The average American spends 8 to 10 hours a day sitting — and generally doesn’t get enough exercise.
Prolonged sitting is linked to everything from fatigue and urinary tract problems to diabetes and cardiovascular disease.
And reports on those risks have given rise to adoption of standing desks.
According to the Centers for Disease Prevention and Control, 87 percent of workers who changed from a standard desk to a sit-to-stand workstation reported feeling more energized, while 66 percent felt more productive and 75 percent felt healthier.
But were they really healthier?
And is prolonged standing at a desk a sustainable, healthy thing to do?
The downsides of standing at a desk
Standing slows blood flow in the loaded muscles, which promotes fatigue and causes pain in the leg, back and neck muscles.
Prolonged and frequent standing also causes blood to pool in the legs and feet, resulting in inflammation of the veins, which can progress to painful varicose veins.
Standing for prolonged periods also immobilizes joints in the spine, hips, knees and feet, which can promote development of arthritis.
You could move your legs as you stand, but that impairs typing and reading, and it’s easy to forget to move once you’re standing and intently focused on your work.
The very real health concerns about prolonged standing — combined with the results of two recent studies — indicate that the standing-desk trend may not have legs.
Instead, it may be that “leg fidgeting” provides a healthier, more practical answer to the risks of prolonged sitting.
Office chairs and artery health: Two clinical studies
Prolonged sitting harms arterial health, particularly in your legs and feet.
It causes arterial stiffness — a risk factor for hypertension and heart attack — and reduces blood flow.
In turn, reduced blood flow reduces “shear stress” — the stress of normal, healthy blood flow on artery walls, which helps keep arteries enlarged and discourages buildup of plaque.
A small clinical study published in 2016 by an international team confirmed that the arterial dysfunction linked to prolonged sitting is caused largely by reduced shear stress.
The authors found that students who sat for three hours with their feet immersed in warm water (108° F / 42° C) showed little reduction in arterial flow-related shear stress, compared with students who sat with dry feet.
To see whether standing also reduces that risk, researchers at Michigan Tech recruited 48 people for a pilot clinical trial.
The Michigan team categorized each participant as belonging to one of four groups:
- Physically fit AND stands for most of the day
- Low fitness level AND stands for most of the day
- Physically fit AND sits for most of the day
- Low fitness level AND sits for most of the day
They put the participants through a walking test to determine their fitness levels and conducted arterial tests to determine pulse wave velocity — an indicator of arterial health and flexibility.
The participants also answered a questionnaire about weekly physical activity, and researchers measured the volunteers’ blood pressure and body fat levels.
Unsurprisingly, younger participants and people with higher fitness levels had less abdominal fat and better arterial health.
Importantly, standing versus sitting did not seem to predict artery health, while fitness level (regardless of office practices) were the key.
Compared with standing most of the day, higher activity levels, more frequent exercise, and better eating habits had bigger beneficial effects on arterial health.
But those results leave open the question of whether frequent movement while sitting, or frequent breaks from the chair, would have equal or even better effects on arterial health.
The answer to that question — judging by the results of a recent University of Illinois study — is that you can in fact gain similar or greater benefits by moving frequently while you sit to work or watch TV.
The NEAT way to boost metabolic rate
Researchers from the University of Illinois at Chicago wondered if regular movement could help undo the negative impacts of prolonged sitting.
You’ve probably heard about people using treadmills at the desk, so they can walk slowly as they work.
That will certainly aid arterial and overall cardiovascular health — but it’s not easy to type and focus on a computer screen while you’re walking.
The alternative is something called “non-exercise active thermogenesis”, or NEAT.
Thermogenesis simply means the generation of internal heat through burning of stored calories.
You can produce NEAT via activities that range from fidgeting to using a movable footrest that keeps your legs in motion
Of course, fidgeting or otherwise moving won’t help arterial health in your legs unless it involves those limbs.
Fortunately, manufacturers offer devices that keep your lower body moving while you work.
The Chicago team recruited 16 people for a study designed to measure the differences in metabolic rate produced by three different workstation scenarios (Horswill CA, et al. 2017):
- Sitting while using a movable footrest (HOVR).
The participants rotated through each of the three workstations, spending 15 minutes at each: seated, seated with the HOVR, and then standing.
Their metabolic and heart rates were measured before the start of the study and after each 15-minute interval.
Encouragingly, the results showed that, compared to sitting alone, sitting while using the movable footrest raised participants’ metabolic rates by an average of 17.6 percent.
And — versus simply standing — using a movable footrest raised a volunteer’s metabolic rates by an average of 7 percent.
While those rises in metabolic rate — and accompanying rises in blood flow — are certainly beneficial, the advantage of the movable footrest versus standing wasn’t particularly substantial.
That said, prolonged standing at a desk is known to cause swelling and pain in the lower limbs, so you need to consider those additional benefits of using a movable footrest or similar device.
As the Chicago team wrote, “Modest movement while seated… might be a reasonable strategy to help elevate NEAT during the workday.”
Ways to keep moving, healthily
It’s clear that even minor but continuous movement while seated aids artery health.
So, if you must sit for work, consider using an HOVR-like device, and walk around or perform indoor exercises or stretching every hour or so.
Or, you can replace your office chair with an inflatable therapy ball — you’ll use your leg and core muscles to stay upright, the ball will encourage continuous but un-disruptive movement, and sitting this way will burn a few extra calories.
And the results from Michigan show that routine exercise provides some — albeit likely insufficient — protection from the adverse effects of prolonged sitting.
Aim for at least 30 minutes of reasonably vigorous exercise per day, five days a week, and be sure to engage in both aerobic and resistance/strength exercise.
- Cabanas-Sanchez V, et al. Changes in sitting time and cardiovascular mortality in older adults. Am J Prev Med. 2018 Mar;54(3):419-22.
- Christensen K. Does standing at work mean healthier arteries? Perhaps not, but exercising and eating well does. http://www.mtu.edu/unscripted/stories/2017/november/does-standing-work-mean-healthier-arteries-perhaps-not-but-exercising-eating-well-does.html.
- Dempsey PC, et al. Prolonged uninterrupted sitting elevates postprandial hyperglycaemia proportional to degree of insulin resistance. Diabetes Obes Metab. 2018 Feb 12. [Epub ahead of print.]
- Dempsey PC, et al. Prolonged uninterrupted sitting increases fatigue in type 2 diabetes. Diabetes Res Clin Pract. 2018 Jan;135:128-33.
- Horswill CA, et al. Effect of a novel workstation device on promoting non-exercise activity thermogenesis (NEAT). Work. 2017;58(4):447-54.
- Morishima T, Restaino RM, Walsh LK, Kanaley JA, Fadel PJ, Padilla J. Prolonged sitting-induced leg endothelial dysfunction is prevented by fidgeting. Am J Physiol Heart Circ Physiol. 2016 Jul 1;311(1):H177-82. doi: 10.1152/ajpheart.00297.2016. Epub 2016 May 27.
- Padilla J and Fadel PJ. Prolonged sitting leg vasculopath: contributing factors and clinical implications. Am J Physiol Circ Physiol. 2017 Oct 1;313(4):H722-H728.
- Park HJ, et al. Sitting time, physical activity and the risk of lower urinary tract symptoms: a cohort study. BJU Int. 2018 Mar 20. [Epub ahead of print.]
- Restaino RM, Walsh LK, Morishima T, Vranish JR, Martinez-Lemus LA, Fadel PJ, Padilla J. Endothelial dysfunction following prolonged sitting is mediated by a reduction in shear stress. Am J Physiol Heart Circ Physiol. 2016 Mar 1;310(5):H648-53. doi: 10.1152/ajpheart.00943.2015. Epub 2016 Jan 8.