Too much of a good thing
By Richard Sutton
One of the most prolific and prominent Torah scholars, Maimonides, once said, “As long as a person exercises and exerts himself, sickness does not befall him and his strength increases. But one who is idle and does not exercise, even if he eats healthy foods and maintains healthy habits, all his days will be of ailment and his strength will diminish.”
More than 800 years later, science is echoing these insightful words.
In 2012, the Journal of Aging Research published an extensive analysis of the literature with respect to lifespan and its relationship to physical activity. The outcomes of the review showed that regular aerobic exercise is associated with significant increases in life expectancy and lowered disease risk. Although the average increase in lifespan was around four years, some studies report increases as high as seven years. For many, the abstract notion of gaining a few extra years has moderate appeal in relation to the effort required, especially early in life. That being said, exercise, and in particular aerobic exercise, offers far more than increased lifespan – it promotes healthspan.
Healthspan describes freedom from disease and the ability to maintain maximum functionality throughout life within the cognitive, physical, and emotional space. Health organisations like the NHS in England; the Centre for Disease Control in the USA, as well as prominent medical schools like Harvard highlight the value of regular exercise. In particular, aerobic exercise has been shown to improve cardiovascular function; prevent certain cancers, osteoporosis and type II diabetes; promote optimal weight ranges and improved sleep; increase physical strength, as well as positively influence mental health (including depression and anxiety). Data from the Copenhagen City Heart study, involving 20 000 participants who were carefully monitored over a 35 year period, showed that 1 to 2,4 hours of moderate intensity jogging per week reduced the risk of fatal diseases by 44%. An increase in lifespan of around six years was associated with these activity levels.
A large Taiwanese study, involving over 415 000 individuals who were monitored over a 12 year period, showed that as little as 15 minutes of aerobic exercise a day increased lifespan by three years and reduced the risk of developing chronic diseases by 14%. The study also showed that for every 15 minutes of additional exercise per day, disease risk was reduced by 4%. The study, which was published in the prestigious journal The Lancet, clearly defined ideal parameters in promoting longevity and health. According to the authors, light aerobic activity (easy jogging, brisk walking) offered maximum benefits up to 110 minutes, translating to a 35% reduction in all-cause mortality. However, no further benefit was realised when exceeding this time span. Intense exercise offered greater health protection (almost a 50% lower risk of developing a chronic disease) but not beyond 50 to 60 minutes of activity. A 15-year observational study of 52 000 adults showed that runners had a 19% lower risk of developing fatal diseases compared with non-runners, but what was interesting was the appearance of a U-shaped curve for distance, speed, and frequency. Running distances of about 8 to 32 km per week; speeds of 10 to just over 11km per hour; and frequencies of 2 to 5 days per week were associated with considerable health protection. The study showed, however, that exceeding these parameters (longer distances, faster paces, and more frequent runs) not only was not associated with greater benefit, it, in fact, detracted from health.
Cardiologist, Dr James O’Keefe, one of the most highly regarded medical specialists in the United States, has been researching the adverse effects of prolonged intense aerobic exercise for years and his findings are concerning to say the least. In a 2012 article published in the British Medical Journal, O’Keefe states, “At best, chronic extreme exercise appears to cause excessive ‘wear-and-tear’ on the heart, prompting adverse structural and electrical remodelling, which offsets some of the benefits and longevity improvements conferred by moderate physical activity.”
The worst-case scenario is a somewhat bleaker picture.
According to O’Keefe, high-intensity exercise sessions lasting beyond 1 to 2 hours result in volume overload in certain chambers in the heart, which can result in overstretching and micro-tears of the heart muscle (myocardium). This makes sense when one considers the basic demands placed on the heart. At rest, the heart pumps five litres of blood per minute. With vigorous activity, cardiac output can increase to 35 litres of blood per minute. While we are well designed to cope with these demands in shorts bursts (up to 60 minutes), protracted periods can lead to tremendous strain.
Four years ago, the European Heart Journal published a study in which a group of 40 highly trained aerobic athletes were evaluated after competing in endurance events including marathon (3 hours), half-ironman triathlon (5,5 hours), full-ironman triathlon (11 hours), and alpine bicycle race (8 hours).
The researchers found that these intense endurance exercise efforts caused dramatic elevations in biological markers of injury to the heart. Additionally, of this group of endurance athletes, 12,5% had significant scarring of the heart. It appeared that the more experienced athletes had a greater degree of cardiac compromise. The study did show that within a week following intense exercise, a full recovery could be achieved, provided there was adequate rest. Several studies, however, suggest that with years of excessive exercise and repetitive injury, this pattern of trauma can lead to patchy fibrotic tissue within the heart, creating the potential for arrhythmias (irregular beating). Additionally, O’Keefe says that long-term excessive exercise may accelerate aging in the heart, as evidenced by increased coronary artery calcification, ventricular dysfunction, and stiffening large artery walls. Two very recent studies published in the Journal of Molecular Medicine also suggest that long distance runners may have increased levels of atherosclerosis (fatty deposits on the arterial walls) and coronary heart disease. For those with existing heart issues, aerobic exercise is associated with reductions in cardiovascular mortality, but only up to a point. A 2014 study of 24 000 patients with coronary heart disease with personal history of myocardial infarction (heart attacks) showed that cardiovascular benefits were reduced when running doses of more than 48km per week or walking more than 74km per week were exceeded.
What the science is repeatedly showing is that physically inactive individuals are the highest risk group for developing health issues and that the most physically active groups (those exercising strenuously on a daily basis) are also at increased risk in terms of all-cause and cardiovascular mortality, when compared with moderately active individuals. In a German study of 1038 individuals with stable coronary heart disease, the most sedentary group had a 100% increased risk of heart attacks or strokes and a 400% higher risk of death when compared with the moderately active group. Those who performed strenuous exercise on a daily basis were also twice as likely to die of heart attack or stroke, compared with the moderately active individuals.
Unfortunately the modern world is one of extremes. On the one end of the spectrum obesity and inactivity have soared to record levels; while on the other end there has been a 2500% increase in marathon participation over the last 40 years. A recent survey of 500 000 adults in the United States reported that about 50% don’t exercise enough. Other studies show that 5% of the general population are completely over exercising. In the interests of healthspan and longevity, both groups need to relook at their exercise habits and make a few tweaks.
For the enthusiast:
- Limit vigorous aerobic exercise to 60 min/day.
- 5 hours of intense aerobic exercise a week is an ideal dose for health and life expectancy.
- It is important to take 1 to 2 days off vigorous exercise per week.
- For those who are training for athletic events and require sessions exceeding 2 hours, make sure they are spaced 6 to 7 days apart so as to promote normalisation within the heart.
- Incorporate more interval training as it is a great way to reduce chronic strain on the heart and it provides enormous fitness returns.
For the less active:
- Walk more! Studies show that the cardiovascular benefits of walking and running are equivalent, provided that you burn the same number of calories.
- Try to perform 1 to 2,5 hours of aerobic exercise weekly (power walking, running, cycling, swimming).
- 2 to 3 sessions a week provide great health returns.
- When time is limited, even a 15 minute session will offer tremendous benefit.
NB: It is strongly recommended that you consult with your doctor before starting any new exercise routine, especially if you have existing health issues.
For more on this and other health topics go to: www.suttonhealth.co.za