Just Three Hours of Sitting Can Damage Your Blood Vessels
By Dr. Mercola
Increasing research has highlighted the significant risk of excessive sitting for adults, but “grown-ups” are not the only ones at risk. Children spend more than 60 percent of their waking day sedentary,1 and by some estimates children sit an average of 8.5 hours a day.2
Further, activity levels are thought to decline steeply after age 8, especially among girls.3 Researchers decided to study a small group of girls (aged 7 to 10 years) to determine if sitting is as detrimental to their health as it appears to be to adults.
In adults, sitting for hours leads to constricted arteries in your legs, which impedes blood flow, raises blood pressure, and contributes to the development of heart disease over time.4 Does the same hold true among children?
Just Three Hours of Uninterrupted Sitting Reduces Vascular Function
At the start of the study, all of the girls had healthy arterial function. However, after sitting for three hours, playing on tablets or watching movies, there was a “profound” reduction in vascular function.5
Arterial dilation fell by up to 33 percent in the girls, which is alarming since a 1 percent decline in vascular function is known to increase heart disease risk by 13 percent in adults.6
There were some encouraging findings. The girls’ artery function had returned to normal a few days later when they returned to the lab. And when the sitting time was interrupted by a gentle 10-minute cycling session, no decline in vascular function was recorded.
Still, no one knows what affect sitting for hours day after day has on kids’ health, so it’s best to encourage your kids to stay active. Study author Dr. Ali McManus, an associate professor of Pediatric Exercise Physiology at the University of British Columbia in Kelowna, told The New York Times:7
“It seems clear from our results that children should not sit for prolonged, uninterrupted periods of time.”
Alan Hedge, professor of Ergonomics at Cornell University, who was not involved in the study, add to CNN:8
“This research suggests that children are not that different from adults in terms of fundamental physiology of the body… It confirms that sitting compresses blood vessels in young people just as much as it does in adults [and] just as much as it does in elderly.”
Why You (and Your Kids) Should Strive to Sit Less Than Three Hours a Day
On average, a US adult spends nine to 10 hours each day sitting,9 which is so much inactivity that even a 30- or 60-minute workout can’t counteract its effects.10 While it might seem natural to sit this long, since you’ve probably grown used to it (physically and mentally), it’s actually quite contrary to nature.
Studies looking at life in agriculture environments show that people in agrarian villages sit for about three hours a day. Your body is made to move around and be active the majority of the day, and significant negative changes occur when you spend the majority of the day sedentary instead.
The Mind Unleashed featured a particularly noteworthy description of what happens in various areas of your body after prolonged sitting.11 You may be surprised to learn that it affects your entire body, from your brain to your feet.
• Heart: When you sit, blood flows slower and muscles burn less fat, which makes it easier for fatty acids to clog your heart. Research published in the Journal of the American College of Cardiology showed that women who sit for 10 or more hours a day may have a significantly greater risk of developing heart disease than those who sit for five hours or less.12
• Pancreas: Your body’s ability to respond to insulin responds after just one day of excess sitting, which leads your pancreas to produce increased amounts. This may lead to diabetes.
Research published in Diabetologia found that those who sat for the longest periods of time were twice as likely to have diabetes or heart disease, compared to those who sat the least.13
Sitting for more than eight hours a day has also been associated with a 90 percent increased risk of type 2 diabetes.14
• Colon Cancer: Excess sitting may increase your risk of colon, breast, and endometrial cancers. The mechanism isn’t known for certain, but it could be due to excess insulin production, which encourages cell growth, or the fact that regular movement boosts antioxidants in your body that may eliminate potentially cancer-causing free radicals.
Findings presented at the 2015 Inaugural Active Working Summit also found that sitting increases:15
- Lung cancer by 54 percent
- Uterine cancer by 66 percent
- Colon cancer by 30 percent
Another reason for this increased cancer risk is thought to be linked to weight gain and associated biochemical changes, such as alterations in hormones, metabolic dysfunction, leptin dysfunction, and inflammation — all of which promote cancer.
• Digestion: Sitting down after you’ve eaten causes your abdominal contents to compress, slowing down digestion. Sluggish digestion, in turn, can lead to cramping, bloating, heartburn, and constipation, as well as dysbiosis in your gastrointestinal tract, a condition caused by microbial imbalances in your body. According to Microbial Ecology in Health and Disease:16
“There is growing evidence that dysbiosis of the gut microbiota is associated with the pathogenesis of both intestinal and extra-intestinal disorders. Intestinal disorders include inflammatory bowel disease, irritable bowel syndrome (IBS), and celiac disease, while extra-intestinal disorders include allergy, asthma, metabolic syndrome, cardiovascular disease, and obesity.”
- Your brain function slows when your body is sedentary for too long. Your brain will get less fresh blood and oxygen, which are needed to trigger the release of brain- and mood-enhancing chemicals.
• Strained Neck and Shoulders: It’s common to hold your neck and head forward while working at a computer or cradling a phone to your ear. This can lead to strains to your cervical vertebrae along with permanent imbalances, which can lead to neck strain, sore shoulders, and back.
• Back Problems: Sitting puts more pressure on your spine than standing, and the toll on your back health is even worse if you’re sitting hunched in front of a computer. It’s estimated that 40 percent of people with back pain have spend long hours at their computer each day.
The disks in your back are meant to expand and contract as you move, which allows them to absorb blood and nutrients. When you sit, the disks are compressed and can lose flexibility over time. Sitting excessively also increase your risk of herniated disks.
Personally, after I reduced my normal 12 to 14 hours of daily sitting to under one hour, the back pain I’d struggled with for decades disappeared.
• Standing requires you to tense your abdominal muscles, which go unused when you sit, ultimately leading to weak abdominals.
• Hip Problems: Your hips also suffer from prolonged sitting, becoming tight and limited in range of motion because they are rarely extended. In the elderly, decreased hip mobility is a leading cause of falls.
Sitting also does nothing for your glutes, which may become weakened, affecting your stability and the power of your stride when walking and jumping.
- Varicose Veins: Sitting leads to poor circulation in your legs, which can cause swelling in your ankles, varicose veins, and blood clots known as deep vein thrombosis (DVT).
- Weak Bones: Walking, running, and engaging in other weight-bearing activities lead to stronger, denser bones. Lack of activity may cause weak bones and even osteoporosis.
Standing Desks May Benefit Kids and Adults
Frequent fidgeting, restlessness, or squirming are often used to describe symptoms of attention-deficit hyperactivity disorder (ADHD) in children. But many would argue that such behaviors are natural when children are forced to “sit still” for unnaturally long periods of time – like the majority of a school day.
To combat this problem, some forward-thinking schools are giving children more opportunity to move around throughout the day, rather than expecting them to sit for hours in desks. For instance, at Vallecito Elementary School in San Rafael, California, at least four classes have introduced chair-less standing desks.17
After an initial adjustment period, the standing desks have been met with rave reviews. The students report the desks are “fun” and help them feel “more focused.” Teachers say the desks make children more attentive and parents say their kids are sleeping better at night… all while avoiding the risks of excessive sitting time; a win-win situation all around! Similarly, Naperville Central High School in Illinois implemented a special program where students could take part in a dynamic gym class at the beginning of the day and had access to exercise bikes and balls throughout the day in their classrooms.
Those who participated nearly doubled their reading scores and math scores increased 20-fold.18 The results speak for themselves… and they extend to adults, too. If you work in an office environment, converting your workstation to a standing desk is one of the best ways to cut back on your sitting time. A study published in the journal Preventive Medicine analyzed 23 active desk studies and found they reduced sedentary time and improved mood.19 Additional benefits from from standing desks included:20
- Standing desks boosted heart rate by about eight beats per minute, while treadmill desks increased it by 12 beats per minute
- Standing desks may boost HDL (good) cholesterol
- Using a standing desk for three months led to weight loss
- People who use standing desks report less fatigue, tension, confusion, and depression, and more vigor, energy, focus, and happiness
Regular Movement Is Crucial for Staying Healthy
As you cut back on sitting, the point is not to simply stand still instead. Fortunately, as you stand up, you’ll likely naturally move as well. According to Dr. James Levine, author of the book Get Up!: Why Your Chair Is Killing You and What You Can Do About It:
“When somebody gets a standing desk, they generally stand for several hours a day. But they don’t stand still. A couple of things happen. The first thing that happens is, they generally move from leg to leg and generally change their body posture quite a lot. That weight-bearing and adjustment of weight-bearing has a whole series of physiological benefits to the musculature, the balance in musculature, the visual cortex, the testicular system, and so on.”
Even movements such as fidgeting appear beneficial. Among women who reported sitting for seven hours or more a day and hardly fidgeting, the risk of all-cause mortality increased by 30 percent. Women who reported fidgeting often fared far better – after sitting for five to six hours a day, their risk of mortality decreased. Further, there was no increased mortality risk from longer sitting time in either the “middle” or “high” fidgeting groups.21
Another example, people who made a point to get up and walk around for two minutes out of every hour increased their lifespan by 33 percent compared to those who did not.22 Those who stood up for two minutes an hour did not reap the benefits that those who walked for two minutes did. Setting a goal of 7,000 to 10,000 steps a day (which is just over three to five miles, or 6 to 9 kilometers) can go a long way toward getting more movement and less sitting into your life. This should be over and above any exercise regimen you may have.
I personally am doing about 14,000 to 15,000 steps a day, which I can typically accomplish with a 90-minute walk. Tracking your steps can also show you how simple and seemingly minor changes to the way you move around at work can add up. I recommend using a pedometer, or better yet, one of the newer wearable fitness trackers to keep track of your daily steps. Other simple ways to increase your physical movement and avoid sitting down at work and elsewhere include:
- Organize the layout of your office space in such a way that you have to stand up to reach oft-used files, the telephone, or your printer, rather than having everything within easy reach.
- Use an exercise ball for a chair. Unlike sitting in a chair, sitting on an exercise ball engages your core muscles and helps improve balance and flexibility. Occasional bouncing can also help your body interact with gravity to a greater degree than sitting on a stationary chair. But this is a concession and it is still sitting, so standing would be a better option.
- Alternatively, use an upright wooden chair with no armrest, which will force you to sit up straight and encourage shifting your body more frequently than a cushy office chair.
- Set a timer to remind you to stand up and move about for at least two to 10 minutes each hour. You can either walk, stand, or take the opportunity to do a few simple exercises by your desk, like those mentioned above.
Tips for Keeping Your Kids Moving, Too
It’s just as important for children and adolescents to remain active throughout the day as it is for adults. Younger kids tend to naturally want to be active, so be sure to encourage this movement and activity as much as possible. Unfortunately, as kids get older they may tend to become increasingly sedentary, especially if they have regular access to computers, TV, tablets, and video games.
The researchers of the featured study were actually surprised at how easy it was to get the young girls to stay seated for three hours; they had thought it was going to be a challenge to keep them still, but the girls were happy to oblige.
As a parent, you’ll want to set limits on your child’s “screen time” and encourage not only organized sports and other activities (like dance classes) but also regular active play and taking part in active chores around the house – walking the dog, taking out the trash, raking leaves, etc. If you have a school-aged child, you may want to speak with your child’s educators about ways to incorporate more movement into their hours spent at school. Outdoor playtime, standing desks, gym classes, and providing access to exercise bikes and exercise balls are just several examples.
It’s also imperative that you act as a role model by staying active yourself. If your kids see you moving around often and sitting less, they will naturally follow suit.