By Gabe Mirkin, M.D.
People who lie in bed without moving day after day suffer progressive weakening of their heart muscle. Eventually the heart becomes too weak to pump enough oxygen to the brain, they stop breathing and die from heart failure. A recent study on mice shows how this is likely to happen.
Preventing mice from using their hind limbs for just 28 days interfered with normal function of mitochondria in cells so that blood levels of oxygen dropped, preventing the sub-ventricular zone of the brain from maintaining normal nerve function and making new nerves (Frontiers in Neuroscience, May 23,2018).
The study showed that preventing mice from using their legs:
• decreased the number of neural stem cells that become nerves by 70 percent, compared to normally exercising mice, and
• prevented precursors to nerves and their insulation cells from becoming fully mature cells.
This may explain how inactivity can eventually cause heart failure and kill you and why diseases that damage nerves that move muscles, such as multiple sclerosis or spinal muscular atrophy, have such high rates of death from heart failure.
Many other studies show that physical activity is necessary for the healthy growth of new nerves during a human lifetime (J. Neurosci. Res, 2016;94:310–317). Bed-ridden people and astronauts in space lose muscle at a frighteningly increased rate. Not using your legs causes loss of nerves that can lead to loss of all muscles, particularly heart muscle, which can eventually cause heart failure and death.
Heart Failure in Primates in Captivity
Monkeys and apes that are kept in zoos have a high rate of death from heart failure, but there is a major difference between primates and humans. Humans die primarily with plaques in their arteries that eventually lead to blocked heart arteries and heart attacks (Circulation, 2007;115:e69–e171), while monkeys and apes in captivity die primarily from heart failure caused by heart muscle being replaced by scar tissue (Evol Appl, 2009 Feb; 2(1): 101–112).
This loss of heart muscle probably comes from the reduced levels of activity forced on them when they are kept in cages. Humans and monkeys have to be active to have healthy mitochondria in their cells. Mitochondria convert sugar and other nutrients into lactate and pyruvate that are necessary for new nerve growth. Low levels of physical exercise are a major risk factor for developing mitochondrial damage that deprives nerve cells of lactate and pyruvate (J. Neurosci. Res, 2005;79:2–10), necessary for the growth of new nerve cells as an animal or person ages (Brain Pathol, 2013;23:613–622).
Plaques in arteries result primarily from a faulty diet, and the diets of monkeys and apes in captivity are tightly controlled so they do not develop plaques. Different types of bacteria that live in your colon turn your immunity on and off. What you eat determines which types of bacteria grow in your colon because these bacteria eat the same food that you do. These colon bacteria determine how quickly you form plaques in your arteries.
Foods favored by the bacteria that turn on your immunity are classified as pro-inflammatory and increase risk for forming plaques in your arteries to increase risk for heart attacks. Anti-inflammatory foods are favored by types of bacteria that help to prevent plaques from forming and decrease heart attack risk. A diet that is high in whole grains, fruits and vegetables, and legumes and nuts is associated with reduced risk for cardiovascular disease, while less healthful diets that are high in sweets, refined grains, juices, red meats and processed meats are associated with increased risk (Journal of the American College of Cardiology, Volume 70, Issue 4, July 2017).
Extensive research shows that diets that are high in meat, sugar and other pro-inflammatory foods cause humans to develop arteriosclerotic plaques in arteries that can lead to blocked heart arteries to cause sudden death of heart muscle (heart attacks).
Regardless of diet, lack of exercise:
• weakens mitochondria, which
• decreases new nerve growth, that
• decreases heart muscle strength and size and can eventually
• weaken the heart so much that it does not have enough strength to circulate blood to the brain and throughout the body.
Thus a heart health program needs to include both a healthful diet to prevent heart attacks (sudden death of heart muscle caused by blocked blood flow to the heart) and physical activity to maintain muscle strength throughout the body to prevent heart failure (progressive loss of heart muscle strength).
Gabe Mirkin, M.D., is a sports medicine doctor and fitness guru. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin has run more than 40 marathons and is now a serious tandem bike rider with his wife, Diana. His website is http://drmirkin.com/. Click to read Gabe's full bio.