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Sitting Will Not Harm Vigorous Exercisers

I think that asking people to stand at work, rather than sit, is harmful advice because standing and not moving is no better than sitting and is just going to make you too tired to exercise vigorously when you are not working. The recent highly-publicized studies that showed sitting is harmful even for exercisers were flawed because they failed to separate casual exercisers from vigorous exercisers. No one has shown that standing up instead of sitting confers any special health benefits, and sedentary standing can cause additional problems such as varicose veins or swollen feet. Standing all day will slow your recovery from your exercise program.

The White House recently requested $700,000 worth of standing desks. I think this is a waste of money. Instead of pushing people toward minimal exercise during work, they should encourage people to exercise more intensely, either in properly-equipped exercise facilities at the workplace or during their leisure time.

Exercise desks with treadmills or pedals should be recommended only for people who are unable to exercise properly. Moving while you are trying to concentrate on work, reading or anything else gives you minimal muscle movement and does not make muscles stronger or increase endurance. To make muscles stronger, you have to damage them with vigorous exercise and when they recover, they become larger and stronger. You cannot increase your ability to take in and use oxygen unless you exercise vigorously enough to become short of breath, and this will never happen at a treadmill desk.

Why the Studies on Harm from Sitting are Flawed
Studies that seem to show that prolonged sitting time is harmful have focused only on single indicators such as self-reported sitting, TV viewing, screen time or traveling in a car (Br J Sports Med, 2015;49:737–42). A recent study corrected for this by analyzing total exercise time. Dr. Richard Pulsford of the University of Exeter in the UK followed 3,720 healthy men and 1,412 healthy women for 16 years and found that total time sitting, time sitting at work, watching TV and during leisure time with or without TV are not associated with increased risk of death (International Journal of Epidemiology, October 9, 2015). The authors corrected their data for age, gender, socioeconomic status, smoking status, alcohol consumption, diet and general health. They showed that prolonged sitting time is not damaging to health if you exercise regularly.

The earlier report that made headlines, from The University of Toronto, reviewed 47 studies and found that sitting for more than eight hours a day was associated with increased risk for death from heart attacks, diabetes, and cancers of the breast, colon, uterus, and ovary, even if a person exercises (Annals of Internal Medicine, 2015;162(2):123-132). The authors believe that people are harmed by spending more than four to five hours a day sitting, driving a car, using the computer or watching television. One study cited in the review showed that people who sit less than eight hours a day have a 14 percent lower risk of being hospitalized. Other studies also associate prolonged time spent sitting with increased risk for weight gain, disease and premature death (Br J Sports Med, Jan 2015;49(2):95-9; J Am Coll Cardiol, 2013 Jun 11;61(23):2346-54). However, virtually none of the people in these studies were doing enough intense exercise to be at a high level of fitness, let alone to be able to compete in sports. The authors define high levels of physical activity as “at least 20 minutes a day of moderately vigorous exercise or at least seven hours a week of moderately vigorous exercise.” This meager amount of exercise is far less than any serious exerciser would do, and is certainly too little to compete successfully in any sport.

Other recent studies have shown that prolonged sitting is associated with increased risk for fatty liver disease (Journal of Hepatology, November 2015;63(5):1229–1237), and greater risk for total cancers in women, but not in men (Cancer Epidemiology, Biomarkers, and Prevention, July, 2015). Neither of these studies separated vigorous exercisers from casual exercisers or non-exercisers.

Why Casual Movement is Less Beneficial than Vigorous Exercise
A high rise in blood sugar causes sugar to stick to the outside surface of every cell in your body and causes significant damage (American J. of Clinical Nutrition, April, 2010; Archives of Internal Medicine, May 2010). Resting muscles pull virtually no sugar from your bloodstream, and insulin is required for the little amounts of sugar the muscles use. Contracting muscles can draw large amounts of sugar from the bloodstream and don’t even need insulin to do so. The more vigorously you exercise,
• the more effectively your muscles remove sugar from the bloodstream without needing insulin, and
• the longer your muscles continue to draw sugar from your bloodstream without needing insulin after you finish exercising (Am J Clin Nutr, 2008(July);88(1):51-57). After a vigorous exercise session, your muscles can continue drawing sugar without needing insulin for up to 17 hours (J Appl Physiol, 2005;99: 338-343 & 2005;8750-7587). Preventing a high rise in blood sugar helps to prevent diabetes, heart attacks, strokes, impotence, dementia and premature death. This is one of the ways vigorous exercise helps to prevent weight gain, diabetes, heart attacks, strokes, cancers and premature death.

Vigorous exercise is also the key to increasing the numbers and size of mitochondria, which helps to prevent overweight, diabetes, heart attacks and certain cancers. See my report from last week, Lactic Acid is Good for You, and More Mitochondria for Better Athletes

Why Vigorous Exercisers Need Rest
People who exercise intensely need to spend a lot of time sitting or lying down because muscles are damaged by intense exercise. If vigorous exercisers and athletes do not rest, their muscles do not heal from their previous intense workouts, and they will be unable to train intensely and are at high risk for injuries.

All successful athletes train by stressing and recovering. They take a workout that is intense enough to damage their muscles, and then they take easier workouts to allow their muscles to recover for their next hard workout. Without the muscle damage caused by intense exercise, muscles do not grow and become stronger. If exercisers don’t spend enough time resting their muscles after an intense workout, their muscles will take longer to heal, which will delay recovery. It will take longer for them to be able to take their next workout, or worse, they may suffer an injury.

Many serious athletes train twice a day or even more. They take an intense workout that damages muscles and within a few hours they develop DOMS (delayed onset muscle soreness). Then they should do easier workouts until the muscles heal and the soreness disappears. Most athletes allow 48 hours between intense workouts. Those who train once a day follow each intense workout with one easy workout. Those who train twice a day follow an intense workout with three easy ones.

How Bicycle Racers Recover during the Tour de France
In multi-day races such as the Tour de France, bicycle racers race flat out over more than 100 miles most days for three weeks. After they finish each day’s race, they immediately eat large amounts of food, drink a lot of fluid and lie down until their next ride. They try to stay still instead of moving and sleep as much as possible. Sleeping helps a person recover faster than sitting awake. Vigorous exercisers and competitive athletes in any sport that requires prolonged, intense exercise should rest their muscles after intense workouts to help them recover for their next workout or competition. For them, prolonged sitting or lying down is unlikely to increase risk for diabetes, heart attacks or any other disease.

Sitting is Harmful for Non-Exercisers at Any Age
Older people who move around live longer than those who are consistently sedentary, and sedentary older people who become more active live longer than those who remain sedentary (Med & Sci in Spts & Ex, Aug 2013;45(8):1501-1507). The more time people sit, the more likely they were to:
• have a big belly (a sign of high blood sugar levels)
• have high blood pressure
• have high HBA1C blood test (a measure of high blood sugar)
• have a high CRP blood test (a measure of inflammation)
• have higher blood sugar levels
• have heart disease
• have diabetes
• be a smoker
• be overweight
To protect yourself from the health consequences of sitting for more than 10 hours a day, you need to stop sitting so much or exercise longer and more intensely to compensate for the hours spent sitting. See Don’t Just Sit at Any Age

Checked 9/1/17

 

October 25th, 2015
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About the Author: Gabe Mirkin, MD

Sports medicine doctor, fitness guru and long-time radio host Gabe Mirkin, M.D., brings you news and tips for your healthful lifestyle. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin is a graduate of Harvard University and Baylor University College of Medicine. He is board-certified in four specialties: Sports Medicine, Allergy and Immunology, Pediatrics and Pediatric Immunology. The Dr. Mirkin Show, his call-in show on fitness and health, was syndicated in more than 120 cities. Read More
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