In the largest study so far of accelerometer-measured physical activity, 96,476 healthy men and women in Great Britain (mean age 62 years) wore wrist accelerometers for one week and were then followed for an average of 3.1 years (Nature Medicine, Aug 17, 2020). During the follow-up period, 732 deaths occurred. The people who were more active had a lower risk of dying, and adding intensity to their exercise increased that protection.

The accelerometers measured energy usage in kilojoules per kilogram per day (kJ/kg/day). The researchers divided participants based on their total energy expenditure and the intensity of their periods of exercise, and found that:
• Those who averaged 20 kJ/kg/day through active exercise were a third less likely to die compared to those who averaged 15 kJ/kg/day with at least 10 percent moderate intensity activity. The difference between those two groups was equal to a 35-minute daily walk, with an extra two minutes at a brisker pace.
• Those who averaged 30 kJ/kg/day were half as likely to die, compared to those who averaged 15 kJ/kg/day. If 30 percent of their exercise was moderately intense, they were only a quarter as likely to die. In other words, those who walked for an hour day, half of which was done at a moderate pace, reduced their risk of death by more than 50 percent.

In another study, researchers reviewed eight studies using accelerometers to follow 36,383 adults, 40 years of age and older, for six years. They found that exercising regularly in adulthood, regardless of intensity, was associated with reduced risk for early death, while sitting for more than nine hours was associated with increased risk for premature death (Brit Med J, August 21, 2019). The risk of death dropped progressively as light physical activity increased up to five hours per day and moderate activity increased up to 24 minutes per day.
• light activity included walking slowly, cooking and washing dishes
• moderate activity included brisk walking, vacuuming or mowing the lawn
• vigorous activity included jogging or carrying heavy loads
Lack of physical activity increases a person’s chances of suffering a heart attack, while a regular exercise program helps to prevent heart attacks (Eur Heart J, 15 January 2019). Not exercising regularly also worsens diabetes (Cardiopulm Phys Ther J, 2013 Jun;24(2):27–34).

Benefits of Intense Exercise
Richard A. Winett of Virginia Tech reviewed 106 journal articles and found that intense exercise can benefit health, prevent disease and prolong lives (Innovation in Aging, July 26, 2019;3(4):1–15). If you are trying to lose weight, intense interval training may help you lose more weight than slower continuous training. A review of 41 studies involving 1115 people shows that people who have limited time to exercise will gain more health benefits from short bursts of intense exercise with short rests between each interval compared to continuous training (Brit J Sports Med, Feb 14, 2019;53(10)). Ideal sports for interval training include running, fast walking, cycling and weight lifting. However, intense exercise can increase risk of injuries.

My Recommendations
Each day that you spend not moving your muscles weakens your heart, so you may eventually die of heart failure. When an obituary says a person died of “natural causes,” that often means the cause was heart failure, usually because they spent their last months or years moving very little or not at all.

A key to prolonging your life and preventing disease is to keep on moving. Your skeletal muscles circulate blood to your heart, and when you contract a muscle, it squeezes blood vessels near it to pump increased amounts of blood back to your heart. Your heart responds to the extra blood by contracting with greater force that makes it stronger.

Even if you don’t have a specific exercise program, it is healthful to keep on moving for a large part of each day — and harmful just to sit all day long. Mow your lawn, wash your dishes, make your bed, vacuum your house, go out for walks and participate in activities that keep you moving your arms and legs. How to Start an Exercise Program

Caution: Intense exercise can cause heart attacks in people with unstable plaques in their arteries. Check with your doctor before starting a new exercise program or making a sudden increase in your exercise intensity.