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). Researchers followed 2635 people over 60 for two years. Those who were active at the start of the study and continued to be active throughout the study had a death rate of only 75 percent of the consistently inactive group. Those who went from an inactive to a more-active lifestyle had a death rate of 86 percent of those who remained sedentary. Those who decreased their amount of activity had a death rate of 91 percent of those who were sedentary throughout the study.
A second study in the same journal issue showed that casual exercise does not help prevent the increased risk for heart attacks and diabetes caused by spending more than 10 hours a day sitting (Med & Sci in Spts & Ex, Aug 2013;45(8):1493-1500). To protect yourself from the health consequences of sitting 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.
The study followed almost 2000 men and women, all over the age of 65, who wore a special machine to measure how much they were moving during their waking hours. The subjects were then divided into four quartiles based on how many hours a week they spent sitting:
1) Zero to 7.9 hours of sitting each day;
2) 7.9 to 9.2 hours;
3) 9.2 to 10.6 hours; and
4) More than 10.6 hours of sitting each day.
They found that the more time the subjects were sedentary, 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
They also found that the most sedentary subjects were more likely to be older, male, and unmarried.
How Does Sitting for Prolonged Periods Damage Your Health?
If you look at the data presented above, you will notice that people who sit for long periods have higher blood sugar levels as well as the large bellies and overweight that are associated with high blood sugar levels. They are also more likely to be diabetic and suffer high blood pressure, inflammation, and heart disease.
A high rise in blood sugar causes sugar to stick to the outer surface membranes of every cell in your body. Once there, sugar cannot detach from these membranes and eventually is converted to sorbitol that destroys the cells. Contracting muscles can help prevent a high rise in blood sugar by removing sugar rapidly from the bloodstream and not even requiring insulin to do so. This benefit can last maximally for an hour after you stop exercising and disappears completely roughly 17 hours after you finish exercising.
Resting muscles remove no sugar from the bloodstream. Everyone has a rise in blood sugar after eating so the best time to contract your muscles is just before or after you eat. You should not eat late at night because you will suffer your highest rises in blood sugar by going to bed immediately after eating.
What Do These Studies Mean to You?
If you have a job that requires many hours of sitting, getting up and exercising during your work hours would probably hamper your job performance. The best way to prevent the side effects of not contracting your muscles is to exercise intensely every day.