Can you exercise too much?

The American College of Cardiology’s Sports and Exercise Cardiology Leadership Council writes that “small amounts of physical activity, including standing, are associated with a lower risk of cardiovascular disease, but more exercise leads to an even greater reduction in risk of death from cardiovascular disease.” (J Am Coll Cardiol, 2016;67(3):316-329). You are better off exercising than not exercising, and there is no good evidence to support any upper limit to the benefits of exercise.

However, a letter in the Journal of the American Medical Association ((April 19, 2016;315(15):1658) expresses concern that some people may reduce their exercising because of a few studies that seem to show that:
• intense exercise does not prolong life more than casual exercise does, and
• people with heart damage may be harmed by too much intense exercise.
The studies that prompted this letter include:

Studies on Healthy People
• The Copenhagen Study, over 12 years, showed that the death rate for casual and moderate joggers was much lower compared to non-joggers, but there was no additional life extension for high-intensity joggers (J Am Coll Cardiol, 2015;65(5):411-419). However, there were only 36 intense joggers with two deaths out of 1,098 joggers and 3950 non-joggers, so I believe that the honest conclusion is that they did not have sufficient data on intense exercisers to make any comparison.

• The Million Women Study, over nine years, reported that the rate of strokes was the same for vigorous exercisers as for those who did not exercise, whereas those exercising two to three times a week were less likely to suffer strokes (Circulation, 2015;131(8):721-729). However, this study did not correct for differences such as smoking habits or socioeconomic class.

Studies on Heart Attack Patients
• The National Walkers’ and Runners’ Health Studies, over 10 years, showed that heart attack victims who exercised were less likely to die than those who did not exercise as long as they ran less than four miles per day or walked less than eight miles per day (Mayo Clin Proc, 2014;89(9):1187-1194).

• The German KAROLA study, over 8.1 years, showed that patients with coronary heart disease who exercised two to four times a week had a much lower death rate than those who did not exercise. However, the strenuous exercisers had a higher death rate than those who exercised two to four times a week (Heart, 2014;100(13):1043-1049).

A heart attack occurs when the blood supply to a part of the heart muscle has suddenly been shut off completely and that part of the heart muscle dies. Both of these studies suggest that people who have already had some dead heart muscle from a previous heart attack may be at increased risk for irregular heartbeats from long and intense exercise. However, nobody has shown that healthy people with undamaged hearts should limit how hard or how long they exercise.

Exercise is Medicine
Dr. Paul Thompson, who has run 29 Boston Marathons over the past four decades, writes that “there is no known upper limit for moderate-intensity physical activity in healthy individuals, but doses more than 100 minutes a day do not appear to be associated with additional reductions in mortality rates. No dose of vigorous physical activity is associated with higher mortality rates than physical inactivity. Physical activity is one of the best modifiable factors for the prevention of noncommunicable diseases and mortality, so it is important for clinicians to keep emphasizing that exercise is medicine.” (JAMA, November 10, 2015;314(18):1915-1916). Virtually all of the studies on elite athletes show that those who exercise to extremes live longer than their less-active countrymen (Mayo Clin Proc, 2014 Sep;89(9):1195-200).

My Recommendations
Most studies on exercise and longevity show that exercisers are far less likely to suffer heart attacks, diabetes, certain cancers, dementia and premature death. If you do not compete and have a healthy heart, the odds are high that the benefits of any amount of exercise far exceed the chances that you will harm yourself.

If you are an older healthy person who competes in sports, I believe that you are better off exercising intensely rather than spending many hours at a more casual pace. Having purpose and goals is healthful and emotionally rewarding. Everyone should continue to have physical performance goals as he or she ages.

How This 80-Year-Old Exercises
On Tuesdays, Thursdays and Saturdays, I ride my bike in a group for more than 30 miles at close to my fastest pace. On the other four days of the week, I do 50-pedal-stroke intervals almost as fast as I can ride, interspersed with slower riding until I recover. When my legs start to stiffen, I stop the workout. I can usually get in 20 to 30 intervals in a 40-minute workout. My legs are always sore in the morning. If they do not recover and feel fresh after a five-to-10-minute warmup, I take the day off. I also stop my workout if I feel pain in one area that worsens as I continue to exercise. 

Dr. Gabe Mirkin is a Villager. Learn more at


Eighty percent of North Americans have X-ray evidence of osteoarthritis by age 65, and sixty percent have significant joint pain. A recent study compared the size of knee cartilage in:
• 176 skeletons of people who lived from 6000 to 300 years ago (from U.S. museums)
• 1581 skeletons of people who died between 1905 and 1940, during the early industrial era
• 819 skeletons of people who died between 1976 and 2015 during the modern post-industrial era
They found that the incidence of knee osteoarthritis (loss of cartilage) has risen at a frightening rate over the last 50 years, reflecting changes from active agrarian or industrial lifestyles to a post-industrial society in which most people do not do a lot of physical labor and gain too much weight (Proc Nat Acad Sci, August 29, 2017;114(35):9332-9336).

It now appears that osteoarthritis may be a disease of inflammation caused mostly by lack of exercise, being overweight, eating a pro-inflammatory diet and having inadequate vitamin D levels (JAMA, November 22, 2017). For example, knee cartilage has such a poor blood supply that it has to get its nutrients from constant movement and weight bearing that effectively pumps the nutrients into the cartilage. Not moving your knees enough deprives knee cartilage of the nutrients necessary to sustain itself so that the cartilage becomes smaller and weaker. Knee cartilage can be damaged in sports activities or accidents, but less than 10 percent of knee osteoarthritis appears to be related to trauma.

Symptoms of Osteoarthritis
People are usually diagnosed as having osteoarthritis if they:
• have gradually increasing pain in their knees, hips, hands or spine
• are age 40 or older
• have negative results in the standard blood tests for the known causes of arthritis such as gout or psoriasis
• have pain that is usually worse in the morning when a person first gets up. In osteoarthritis, the pain usually lessens as the person keeps moving. In rheumatoid arthritis, the joints often continue to hurt for more than an hour after a person starts moving about.
• if hands are affected, the swelling of the knuckles and joints caused by osteoarthritis is on the ends of the fingers next to the fingernails (not in the middle finger joints) and at the base of the thumb. Rheumatoid arthritis usually affects the middle joints of the fingers and the joints where the fingers attach to the hand.

Evidence of Inflammation
Your immunity is good for you because it kills germs that try to invade your body and works to heal injured tissues. However, after the germ is gone or the wound is healed, your immunity is supposed to slow down. If your immunity remains active, it uses the same chemicals and cells that attack germs to attack you and that includes destroying the cartilage in your joints. Recent research shows that osteoarthritis can be caused by inflammation, the same overactive immunity that causes heart attacks.
• People with osteoarthritis have high blood levels of galectins that turn on a person’s immunity to cause inflammation, just like in rheumatoid arthritis and reactive arthritis (The Journal of Immunology, February 15, 2016;196(4):1910-1921).
• Almost 70 percent of obese people develop knee osteoarthritis (Arthritis and Rheumatism, Sept 15, 2008;59(9):1207-13) and losing as few as 11 pounds reduces risk of developing knee osteoarthritis among women by 50 percent (Arthritis and Rheumatism, August 1998;41(8):1343-55). Excess weight causes inflammation.
• A study of almost 5000 people showed that those who eat a plant-based Mediterranean-type (anti-inflammatory) diet have a much lower prevalence of osteoarthritis (Clin Nutr, Oct 8, 2016).

Exercise Helps to Prevent and Treat Knee Osteoarthritis
• A review of 55 studies showed that weight-bearing exercise reduces pain and improves joint function in people who have osteoarthritis (British Journal of Sports Medicine, September 24, 2015).
• An exercise program to strengthen the muscles around the knee is more effective than removing broken cartilage from knees because the exercise program helped stabilize the knee by strengthening the muscles that control knee movement (Br J Sports Med, Nov 15, 2016;50:1426-1427).
• A randomized controlled study of 126 people with knee osteoarthritis showed that a combined program of aerobic and strength training for 20 weeks markedly decreased knee pain and increased mobility (Arthritis Care & Research, Aug 30, 2016). No serious side effects occurred from the knee strength and conditioning program.
• Exercise strengthens cartilage in women with knee osteoarthritis (Med and Sci in Sprts and Ex. March 23, 2017). High impact exercise for one year strengthened bone and cartilage (J Bone Miner Res, Jan 2014;29(1):192-201).
• A review of six studies of 656 men and women with knee osteoarthritis found that exercise improves symptoms of knee pain in osteoarthritis and that it didn’t make much difference whether the knee exercise program was of low or high intensity (Cochrane Database Syst Rev, Oct 29, 2015;(10):CD010203).
• Knee surgery called arthroscopic partial meniscectomy to trim a torn knee meniscus is one of the most common surgical procedures done in North America, with more than 750,000 knee arthroscopies done in the United States each year, but surgery has not been shown to be more effective than exercise in treating knee osteoarthritis (N Engl J Med, 2013;368:1675-84; Br J Sports Med, 2016;50:1473-1480 ).

My Recommendations
If your joints hurt, try to find out what is causing your pain. Your doctor will do tests to see if you have gout, psoriasis, rheumatoid arthritis or some other known cause. If none are found, you will probably be given a diagnosis of osteoarthritis. If you have sudden locking of your joint and it gets better, and then recurs, you may have “joint mice”, loose pieces of cartilage that slip between the cartilage to cause horrible pain. This can usually be cured by removing these lose pieces by arthroscopy.

Many recent studies show that inflammation may well be the cause of most cases of osteoarthritis and therefore you should:
• lose weight if overweight
• eat an anti-inflammatory diet that includes lots of vegetables, fruit, whole grains, beans, nuts and other seeds, and restricts red meat, all foods and drinks with added sugar and fried foods
• keep blood levels of hydroxy vitamin D above 20 ng/ml

Osteoarthritis always worsens with inactivity, so you need to keep on moving. However, be guided by pain and stop when the pain worsens. You should not run, jump or do sports that involve impact because the force of your foot hitting the ground can break off knee cartilage. Low-impact sports include bicycling and swimming.

It is acceptable to try to ease your pain with NSAIDs (non-steroidal anti-inflammatory drugs), but pain medications do nothing to cure your joint pain and they have many side effects. Take the lowest dose that you need. If the pain becomes so unbearable that it keeps you awake at night, you may want to consider a knee replacement. However, replacing your joint requires driving a spike into the middle of the bones of your knee and that pushes aside the shock-absorbing marrow and weakens the bone to increase your chances of breaking the bones when you fall. In that case, the knee cannot be replaced until the broken bones heal and you may be unable to walk or be bedridden for a very long time. 

Dr. Gabe Mirkin is a Villager. Learn more at