Too much sitting is not just bad for your back
It’s well known that excessive sitting aggravates low back conditions and destabilizes your lumbar spine making you prone to back injury, but recent research links it to life threatening health issues.
Is prolonged sitting really dangerous? Sorry PC folks. The answer is – Yes, it does, according to the Australian Diabetes, Obesity, and Lifestyle Study. In this national survey, researchers followed 8,800 adults, ages 25 and older, for six and a half years and found that each hour subjects spent lolling about watching television was associated with an 18 percent increase in death from heart disease – and an 11 percent increase in overall mortality. Those who watched TV for four or more hours daily were 80 percent more likely to die of heart disease and 46 percent more likely to die overall than those who watched two hours or less.
Researchers say it’s not just the overweight that are in trouble. Even at a healthy weight, sitting for hours can make it harder for the body to process blood sugar and blood fats – an endeavor that requires the chemicals we produce when our muscles contract, as they do when we stand or move. Study authors encourage us to exercise regularly and break up our sitting with movement. Take a walk at lunch, or go talk to your coworker rather than sending an e-mail.
Owen N, Healy GN, Mathews CE, Dunstan DW. Too Much Sitting: The Population Health Science of Sedentary Behavior. Exerc. Sport Sci. Rev., 2010; 38(3): 105-113.
Sedentary behaviors (from the Latin sedere, ‘‘to sit’’) are those behaviors that involve sitting & low levels of energy expenditure. Adults spend most of their waking hours either sitting or in light-intensity activity (standing with some ambulation).
Sitting time, which can commonly be 70% to 80% of our waking hours includes sitting at a desk at work, at home while on computers, game consoles, watching TV, reading, & sitting while driving or as a passenger in automobiles involve prolonged periods of low level metabolic energy expenditure & are associated metabolic biomarkers that place people at risk of chronic diseases & an increased risk of premature all-cause & cardiovascular mortality.
The environment in which humans sit or move in their daily lives has changed rapidly. Changes in transportation, communications, workplace, & domestic entertainment technologies are associated with significantly reduced demands for physical activity. Too much sitting is distinct from too little exercise. Sedentary behavior is not simply the absence of moderate- to vigorous-intensity physical activities, but has potentially deleterious health consequences including obesity and metabolic precursors of major chronic diseases (type 2 diabetes, cardiovascular disease, breast & colon cancers).
Importantly, adults can meet public health guidelines on physical activity, but if they sit for prolonged periods, their metabolic health is compromised.
The Active Couch Potato phenomenon: example an office worker who jogs or bikes to and from work, but who then sits all day at a desk and spends several hours watching TV in the evening. This person spends 71% of his or her waking hours in sedentary time. Thus, it is possible for individuals to be physically active, yet highly sedentary.
Chronic unbroken periods of muscular unloading associated with prolonged sedentary time results in an inactivity physiology that may have deleterious biological consequences.
The loss of local contractile stimulation with sitting leads to the 1. Suppression of skeletal muscle lipoprotein lipase (LPL) activity (necessary for triglyceride uptake & HDL cholesterol production),
2. Insulin resistance & reduced glucose uptake.
One may expect that in future physical activity recommendations from the American College of Sports Medicine (ACSM) & the American Heart Association (AHA) a statement on reducing sitting will be included. Time in sedentary behaviors displaces time spent in higher-intensity physical activity - contributing to a reduction in physical activity energy expenditure.
Standing, which involves isometric contraction of the antigravity (postural) muscles and only low levels of energy expenditure, elicits electromyographic & skeletal muscle LPL changes. With this perspective, standing is not a sedentary activity. Light-intensity activity has an inverse linear relationship with a number of cardiometabolic biomarkers. In addition, breaks in sedentary time (as distinct from the overall volume of time spent being sedentary) were shown to have beneficial associations with metabolic biomarkers.
TV watching: In a 6.5 yr study, high levels of TV time were significantly associated with increased all-cause & cardiovascular disease mortality rates. Each 1-hr increment in TV time was found to be associated with an 11% and an 18% increased risk of all cause and cardiovascular disease mortality rates, respectively. Relative to those watching less TV (<2 hr/d), there was a 46% increased risk of all-cause mortality and an 80% increased risk of cardiovascular disease mortality in those watching TV 4 hr/d or more.
The Metabolic Syndrome: ↑Weight (obesity/overweight), ↑blood sugar, ↑insulin resistance (hyperglycemia), ↑blood fats (hyperlipidemia), ↑blood pressure (hypertension), ↑risk CVD, ↑risk DM II. These increased risks were independent of traditional risk factors such as smoking, blood pressure, cholesterol level, and diet, as well as leisure time physical activity and waist circumference.
A recent US study examined sedentary behaviors in relation to cardiovascular mortality outcomes based on 21 yrs of follow-up of 7744 men. Those who reported spending >10 hr/wk sitting in automobiles (vs <4 hr/wk) and >23 hr of combined television time & automobile time (vs <11 hr/wk) had an 82% and 64% greater risk of dying from cardiovascular disease, respectively.
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