I have to admit that the title is stolen from an article by Mary Sheppard. The article is about the strange phenomenon of athletes keeling over and dying during strenuous exercise. The irony is that a marathoner will probably be the most worn out specimen at the morgue despite having a high VO2max before death.
“If we accept the validity of the general concept of physiological hormesis as being the phenomenon of achieving health beneficial effects by exposure to mild stress, then hormesis is being applied already and successfully to humans. The evidence for this is the well-demonstrated health benefits of regular and moderate exercise.”
Running is good for us. It has to be, we’ve been told so for years and years. There’s just no doubt about it. There usually isn’t much need for running in a modern society, except for perhaps trying to catch a bus or escaping the occasional bully or mugger. But despite the lack of need to run, many of us still prefer to run, and some run a lot. We even learn to enjoy the burning lungs, the taste of blood and a heart rate that would otherwise have us seriously worried. We are mimicking the thrill of the hunt. Humans are truly made to run. But, contrary to our hunting forefathers there is no reward following the hunt. No big mammoth to cut up and bring home. No great mammal that feeds your family for a week and that makes running unnecessary until the meat is gone.
Modern humans do things differently. Instead of following the natural evolutionary approach and wait with exerting ourselves until more food is needed, we run again the very next day, and the day after that, and the day after that. The total amount of physical activity is staggering. There is nothing natural about it. Recreational joggers and marathon runners burn through an extreme amount of energy, usually supported by a high carbohydrate diet. Many also claim they do it for their health. But is it really that healthy?
Exercise is the perfect example of the principle of hormesis. The term is usually used to describe favorable effects of small amounts of something that is unfavorable in larger amounts, like a toxin or a stressor. Exercise is a stressor. If you want to test it, you can start exercising and don’t stop. You will get weaker and weaker until you fall and your body will be in a far worse shape than when you started. Exercise is really and truly bad for us, but only acutely and only if we forget to rest after.
“…the occurrence of SCD [Sudden Cardiac Death] associated to training and competitions for athletes is increased by 2.8 times compared to the average relative risk of non-competitive practitioners, hence giving rise to the following question: Does sports activity causes sudden death in young people?”
It is important to remember that it is the physiological response to exercise, the repairing of damaged tissues, and increasing of tolerability that causes exercise to make us stronger. It is the rest, the restitution that increases our potential, our endurance and our strength. Exercise makes us weak, rest makes us stronger.
Energy and glucose restriction has been shown to increase the lifespan of several species. It also increases formation of reactive oxygen species (ROS) in the mitochondria. The organism however, seem to adapt and acquire an increased resistance to oxidative stress. Antioxidants, which decrease ROS levels, limit the life extending effects of glucose restriction and exercise . It has also been suggested that high antioxidant intakes lessens the adaptive response to exercise. But not all data show this .
The bottom line is that if you want exercise to be healthy, you better learn to rest.
Everybody is free to do what they want and to exercise as they please. But the marathon runner lies, consciously or not, if he says he runs for his physical health. Although top athletes are marvelous examples of how far we can push the boundaries of the human body, they are not in it for the health. Injuries, wear and tear, infections and long term side effects are all part of the deal. This deal also needs to be remembered by recreational runners.
If you run for hours a day, you do it for the joy of exercising. You do it for the brake it gives you from the everyday hassle. You do it for shear competitiveness. But you do not do it for your physical health. That is bollocks.
From a metabolic standpoint is makes little sense to participate in long duration exercise of an intensity that is way over in the carbohydrate burning zone. Our carbohydrate fuel stores are quickly depleted. From en evolutionary standpoint these stores are there for short and intense bouts of exercise. As a hunter or gatherer we would spend most of our time in a fat burning low intensity zone and only occasionally do shorter high intensity work. Imagine foraging or tracking prey or working around the camp – all low intensity physical activities. Or you can watch Robb Wolf and his “caveman” friends hunting big game with atlatls. There is little sprinting involved.
Many runners (or other endurance athletes) however, spend much of their time in a carbohydrate burning zone. I was taught in school that intensities around the anaerobic threshold, where much of the energy (ATP) is produced outside of the mitochondria, are ideal for improving endurance performance. But the long time spent exercising at these intensities, may cause serious problems.
One obvious aspect is that the high intensity exercise many do requires them to stuff themselves with carbohydrates. Stuffing yourself with carbs is probably more of a problem if you don’t exercise much, but it might still be problematic. High carbohydrate for an endurance performer is usually synonymous with high sugar high starch which will in itself have a negative impact on the body. What’s worse is that high starch usually means high grain low fat. The stage is set for gut problems, infections, allergies and asthmas, muscle cramping and soreness, slow wound healing and general poor health. Remember, the apparent absence of disease does not equal good health. Poor diet might be the reason why the 50 year old marathon runner often does not look anything like a healthy human specimen.
But there are other problems, directly related to the exercising itself. One obvious aspect is the amount of wear and tear. The higher intensity exercise you perform the longer restitution needed to fully repair the body. Injuries and frailty is part of the deal. Endurance athletes are more osteoporotic than the rest of us [5-8].
Too little rest and too much exercise results in increased cortisol and other stress parameters. Marathon running is a huge stress to the body. One group of researchers from Canada used data from magnetic resonance imaging (MRI) to find out how marathon running affects the heart over time. Headed by Dr. Eric Larose, the group found that the magnitude of abnormal heart segments was more widespread and significant in a group of less fit runners. Runners with lower VO2max showed more signs of heart injury than more fit runners.
Wu et al  found that a 24hour ultra marathon damaged about every part of the body measured, including the liver and gallbladder. They also found that HDL decreased, LDL increased, red and white blood cell count decreased as well as testosterone. Their conclusion: “Ultra-marathon running is associated with a wide range of significant changes in hematological parameters, several of which are injury related.”
Lippi et al noticed that enzyme biomarkers indicating liver damage are increased after a half marathon run to such a degree that there is no point testing for liver damage close to a race .
Skenderi et al  examined thirty-nine runners competing in the Spartathlon race (a 246km continuous race from Athens to Sparta) who managed to complete the race within a 36h time limit. They found that “Muscle and liver damage indicators were elevated at the highest level ever reported as a result of prolonged exercise…”
There is more data showing muscle damage from this kind of exercising. Warhol et al  found that the muscles of veteran runners had intercellular collagen deposition suggesting repeated injury. Tissue from non runner controls did not show this.
“Since oxidative modifications of DNA can lead to mutations and exceptionally high volumes of exercise are also associated with a substantial oxidative stress, concerns have arisen about the health effects of competing in endurance and ultraendurance exercise events, particularly when participants are not optimally trained.”
As if damaging your muscles and organs weren’t enough, both ultra endurance exercise and half marathon results in DNA damage [13,14]. There is however need for follow up studies of DNA damage and instability. So far the effects are only proven acutely. Rae et al fount that telomere length in the vastus lateralis muscle in experienced endurance runners was inversely related to years spent running and hours spent training . Shortening of telomere length is a sure sign of aging. Collins et al  found that Athletes with exercise-associated fatigue (fatigued athlete myopathic syndrome) had significantly shorter telomere length in their vastus lateralis compared to matched controls. Results from Ludlow et al suggest that hormesis is in fact a factor and that when it comes to telomere length moderate physical activity is better than both low and high levels .
As heart-healthy as running is supposed to be the heart is still one of the body parts placed under the most pressure and cardiac damage is easily measured [18,19]. I was taught in school that endurance exercise increases left ventricular volume and thus produces a greater cardiac output. Strength exercise on the other hand was supposed to increase heart wall thickness because of the high blood pressure, and thus increase the risk of cardiac arrhythmias. I think this is what is called the “Morganroth hypothesis.” Trouble is that much data refute the hypothesis. The most recent comes from Australia, showing increased left ventricular wall thickness after endurance exercise, but not after strength exercise.
Cardiac troponin (part of contraction process in skeletal and cardiac muscle) increases greatly after a half marathon in young runners, and “…reach levels typically diagnostic for acute myocardial infarction…”. The level is higher in less trained athletes . Whether cardiac injury markers are indicative of real damage is uncertain. Jassal et al puts it this way “Elevations of cardiac injury markers in non-elite athletes are extremely common following the completion of endurance events and correlate with the increased endurance time. Whether the increase in the levels of these enzymes represents true myocardial injury or a result of the release of cTnT from the myocytes requires further investigation.”.
“The clinical significance of chronic exposure to endurance exercise is unknown. The development of myocardial fibrosis has been suggested as a long-term outcome to chronic exposure to repetitive bouts of endurance exercise and has been linked to an exercise-induced inflammatory process observed in an animal model. This hypothesis is supported by a limited number of studies reporting postmortem studies in athletes and an increased prevalence of complex arrhythmia in veteran athletes.”
There are other parts of the cardiovascular system negatively affected by extreme exercise. A 96 fold increased serum level of calprotectin after both half and full marathon is indicative of damage to the vascular endothelium and microthrombi .
Marathon running has also been shown to induce kidney damage/renal abnormalities , and especially if you get dehydrated.
It has been suggested that marathon running also induce brain damage, as measured by increase levels of S100beta, a common marker of brain damage. A study from 2004 however, indicates that the increased S100beta levels come from extracranial sources . But it’s still tissue damage. By the way, S100beta is also a marker of cancer.
Exercise breaks us down. Rest is what makes us stronger. There is little indication that marathon running is worth participating in for health reasons. Running is in itself fine, but too much and too high intensity combined with an unnatural diet makes it very unhealthy. If I was to give an advice based on the best of my knowledge for optimal health I would recommend short high intensity exercise such as interval or strength training. Do this 2-4 times a week and keep any other exercise you partake in in a fat burning, moderate intensity zone. This is also an exercise advice that can be easily coupled with low carbohydrate dieting.
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Two thoughts: The only study I'm aware of that compares long-term mortality from runners to non-runners finds that runners have a far lower level of per-annum mortality and disability than fit non-runners.
If Robb and friends were good marathon runners, they wouldn't have needed the atlatls. This would explain how people caught animals for the millions of years prior to the invention of the atlatl.
Tuck, are you implying that marathon runners could catch an elk by sheer feat of running longer than an elk can?
Correlation is not causation. For instance, marathon runners try a great number of healthful lifestyles excluding running marathons that the average population doesn't that could be leading to improved life span overcoming the damage the marathoning inflicts. Much like the belief that nurses taking hormone replacement improved health. Compared to the average person the nurses on hormone replacement were better off, but not because of the replacement therapy.
How'd that estrogen replacement theory work out for us?
One other source of exercise that probably existed in paleo times would be dance. A pertinent question would be does rhythm, music and variation in form in some unknown way ameliorate the downside of exercise?
I loved your blog today! Take a look at this article because it caused a ton of waves when it came out in February.
Diverse patterns of myocardial fibrosis in lifelong, veteran endurance athletes
Wilson, M.1, O’Hanlon, R.2,3, Prasad, S.2, Deighan, A.4, MacMillan, P.5, Oxborough,
D.6, Godfrey, R.7, Smith, G.2, Maceira, A.8, Sharma, S.9, George, K.10 and Whyte, G.10
1. ASPETAR, Qatar Orthopaedic and Sports Medicine Hospital, Doha, Qatar 2. Department of Cardiac Magnetic Resonance Imaging, Royal Brompton and Harefield NHS Trust, London, UK 3. St Vincent's University Hospital and The Blackrock Clinic, Dublin, Ireland
4. Department of Cardiology, St Bartholomew's Hospital, London, UK 5. North Bristol NHS Trust, Frenchay Hospital, Bristol, UK 6. University of Leeds, Leeds, UK 7. Department of Sport and Exercise Science, Brunel University, Uxbridge, London, UK.
8. Cardiac Imaging Unit – ERESA. Hospital Arnau de Vilanova, Spain. 9. Department of Heart Muscle Disorders and Sports Cardiology, St Georges Hospital, UK. 10. Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, UK 2 Running Title: Cardiac Fibrosis in Endurance Veteran Athletes Corresponding Author: Mathew Wilson ASPETAR, Qatar Orthopaedic and Sports Medicine Hospital, 27 PO Box 29222,
Doha, Qatar. Tel: +974 413 2000 30 Fax: +974 413 2027 E-mail: Mathew.email@example.com
Tuck, the Chakravarty study is interesting, but Eric has point about confounding variables not being controlled for. I am not saying running is bad per se, but there is some data, as I illustrated, indicating that too much of too high intensity can be bad.
I know there are groups of people who hunt by tiring out animals, sometimes after poisoning the animal first, but that does not mean it is healthy nor that it is particularly effective.
Anonymous: A good question, but I don't know. Guess it depends on the type of dancing and how much you do it.
john: I can't believe I forgot that one. Thank's for the up.