The reason for writing this post stems from me reading a blog post by Charles Poliquin on his personal blog. Poliquin’s post is a commentary on a recent study on endurance athletes (la Gerche et al, 2011) and a more or less generic assault on endurance training per se. Yes – this man actually claims that endurance training, cardio, is bad for you….
This is very, very problematic for two reasons: 1) because there is an overwhelming likelihood that his claims are wrong, and 2) because Charles Poliquin is an international fitness guru and the owner of one the strongest fitness communication and certification brands in the world, making him extremely influential. When someone this influential makes claims like these, this will almost certainly push some individuals towards making some very poor decisions regarding their health and training and therefore most likely result in a net negative effect on public health. Therefore it crucial that claims like these are met with qualified resistance, even though mine probably won’t generate the same impact with my few thousand readers compared to his (probably) ranging from the hundred thousands to millions of readers ;o)
Before i get to my rebuttal, let me state that I think a training approach where multiple fitness parameters are stimulated is favorable to any approach just including “classic” cardiovascular endurance training. ACSM has defined fitness to include strength, muscular endurance, cardiorespiratory fitness, flexibility and motor skills – which I think of as a very decent definition and that ideally one should aim to target all of these. Furthermore, I fully acknowledgde that a lot of people use cardio in a wrong way considering the existing stress factors in their lives, e.g. putting spinning in a tightly packed schedule in a body with existing sympathetic overstimulation. But this does not justify making false claims against a physical activity that everything indicates is very healthy.
Take a deep breath…
Who the f*** is Charles Poliquin?
I’ve been getting more and more readers in the last couple of months and as I’m not really sure who you are out there, I think It’d be best to present Charles before we do this. He’s a Canadian exercise physiologist, personal trainer and strength and conditioning coach, whose track record as a trainer includes several world champions and Olympics competitors, primarily in hockey and track and field. He rose to fame in part through him writing for Muscle Media and later testosterone magazine, that turned into t-nation as we know it today. He’s developed his own trainer certification brand, PICP and the very succesful (and controversial) nutrition coaching concept Biosignature. In the beginning of his career as a writer he was quite progressive, yet in respect of the academic consensus, but in the last 5-10 years he’s been turning progressively faster towards a standpoint embracing “alternative” viewpoints and in some cases directly opposing the opinion of established academia especially on the topic of nutrition. Of course he claims that everything he says is back by rock hard science, but especially in the later years those claims contrast what most individuals training in nutrition, sport or health science consider a very selective and sometimes just wrong use of scientific literature.
The way I see it, he’s been getting very good at saying the right stuff to make money. That should leave reasonable space for interpretation without getting overly explicit.
What is he saying, really?
In his blog post, he comments on a recent study in which different endurance and ultra endurance athletes had their cardiac function assessed directly post-competitive events. The researchers found that endurance athletes had impaired function of the right ventricle, the part of the heart pumping blood into the lungs.
In his post, he makes a number of rather controversial points/comments:
“Beware of cardiovascular damage from intense endurance training.”
Actually this is not news. It has previously been shown that ultra endurance event may cause a degree of temporary damage to the heart muscle. However, it has not been shown to accumulate in general and not been shown to contribute excessively to net mortality in endurance athletes…
“providing additional data that endurance training may not provide health benefits”
Erm…. Let me get that straight. Because an acute study shows temporary damage to the heart, endurance exercise provides no health benefits? What happened to lower blood pressure, improved glucose uptake, metabolic fitness, insulin sensitivity and reduced peripheral vascular resistance and vasoreactivity?
“Take away from this study the understanding that long duration, intense endurance exercise is unlikely to be beneficial for health.”
Read the previous comment… and i will comment more further down…
“Shorter duration endurance or “aerobic” exercise has not been shown to cause the same damage, but it does produce oxidative stress, which will lead to chronic inflammation and may impair organ function.”
I will deal with that later on..
At the end of the post he naturally accounts for what his answer is to the scourge of endurance cardio is:
“But, I suggest that the ideal exercise for health, well being, and cardiovascular health is a resistance training program that includes intense energy system training for conditioning and weight management. “
Followed by a reference to a previous post of his with the flattering title “The (Many) Negatives of Aerobic Training”, in which he elaborates on his criticism of aerobic exercise (and ultimately links to another article in which he prescribes his treatment for scourge of aerobic, which primarily consists of not doing it (aerobics ;o) and/or a supplementation regime of antioxidants
Lower mortality and morbidity in former elite endurance athletes
I want to initiate my rebuttal by rejecting that the literature supports that aerobic exercise is unhealthy or that endurance athletes put their very health at risk. The available literature on mortality and morbidity of former elite athletes across disciplines, indicates that former elite athletes in endurance sports has longer active and absolute life expectancies than other groups of athletes and the background population (e.g. Sarna et, 1994; Sarna et al, 1997 og Kujala et al, 2003). Of course the very definition of “healthy” is subjective, but my point is that life expectancy is a harder endpoint than acute responses to (ultra)-endurance events like ejection fraction, inflammatory markers and so on.
I fully acknowledge that these studies on mortality are correlative, but they represent the best estimate of health in endurance athletes and the healthiness of their training and they strongly contradict the postulates put forth by Charles Poliquin.
So what does poliquiin claim is unhealthy about aerobic exercise?
In the la Gerche study (2011), the researchers report an impairment of heart function in the right ventricle, the part of the heart pumping deoxygenated blood into the lungs and they also find elevated markers of myocardial damage. This impairment subsides almost totally within two weeks, but the researchers speculated whether continued training and competitive activity could cause chronic myocardial scarring or other types of damage. Some studies do indicate that this happens, although this is only documented in world elite athletes and it has not been documented to result in a these athletes having higher mortalities than background populations.
The most obvious interpretation seems to be that although there may be weak evidence for the prevalence of myocardial damage in a small subset of world elite ultra endurance athletes, the negative effects are countered by the beneficial effects on insulin sensitivity, oxidative defences, lipid profile, peripheral vascular resistance, vasoreactivity and so on.
Normally, we think of the heart as an unstoppable machine, that never stops, never gets fatigues and whose function is incredible stable. Therefore, when cardiologists, used to working with dysfunctional hearts, looks at a heart whose function is impaired following extreme competitive endurance events, they assume it is a sign of pathology. If one looked the same way at skeletal muscle following the same events or extreme or unaccustomed resistance training, the skeletal muscle tissue would appear to suffer from some sort of myopathy, suffering from loss of structural integrity, reduction of strength and leaking creatine kinase and myoglobin. All of these could also be signs of dangerous muscle ailments, but with skeletal muscle, these are considered “natural physiological” signs, rather than something pathological. Even after repeated muscle damage following intense exercise, we see no discernible scarring or fibrosis in young healthy individuals. Considering how close cardiac muscle and skeletal muscle are related to each another, I can’t help thinking that the observed changes in cardiac muscle are physiological rather than pathophysiological, considering that the impairment of right ventricle function seems to be fairly consistent, whereas the prevalence of proposed training-induced actual cardiac scarring or chronic damage is quite rare.
Poliquin’s really got a stick up his arse about cardio
In the previous post that Poliquin links to in his post, he extends on his criticism on aerobic exercise. In that post he arranges his points of criticism in different point, that I’ll divide a little further, as most of his point actually contains two points. He claims, that aerobic exercise:
- increases cortisol (implied to an extent in which i damages health)
- promotes aging
- causes increased inflammation
- increases oxidative stress
- reduces levels of circulating sex hormones
- reduces size of primary and secondary sex organs (!?)
- compromises immune function
Claims 1 and 2 are derived from a study in which the researchers measured levels of cortisol in hair from endurance athletes (Skoluda et al, 2011) and found that endurance athletes have elevated levels of cortisol. This is not a mystery by any means – all intense training causes increases in cortisol and given this circumstance it’s no big deal that endurance athletes that usually trains for longer time than e.g. strength athletes also has more cortisol in their hair. Cortisol is amongst other uses, used for mobilizing energy reservoirs in the body (including muscle protein), especially when glycogen stores are depleted, which happens frequently when endurance athletes train. This however, does not imply that the observed exercise-induced increases in cortisol are unhealthy.
So the point where Poliquin’s pushing it, is where he claims that increased cortisol is unanimously bad and not a part of the primary training response. There’s pretty substantial evidence that cortisol reduces fatigue perception through direct effects on the central nervous system and also some evidence that i actually increases fatigue tolerance peripherally by increasing ion transporters that helps maintain membrane potential, which is a known factor in momentary muscle fatigue. Finally it must be said that endurance athletes seem to develop a resistance to cortisol which once again should reduce the physiological impact of the fact that they have net higher cortisol..
Claims 3 and 4 stems from another study, where the investigators measured the levels of free radicals and peroxidized lipids, which are markers for oxidative stress, in controls, sprinters and long-distance runners (Marzatico et al, 1997). In their paper, they report higher levels of these compounds in the long-distance runners. Free radicals and peroxidized lipids are produced during regular metabolism and sometimes these compounds escape the metabolic clockwork and escape or overcome the built-in defenses. This can lead to DNA and cell membrane damage, which is obviously not good. Besides that, they generally contribute to inappropriate inflammatory cascade activation.
As these compounds are byproducts of metabolism it makes sense that more are produced in long-term sustained activity, relative to short-term or no activity. After all, it does require more metabolizing to rung 42 km that 200 m. And again, where Poliquin logic fails is when he extrapolates from the acute situation to the chronic. As already discussed, it is not surprising that more byproducts of oxidation can be found in endurance athletes, but it cannot be used to claim that these athletes are overwhelmed by oxidative stress in general, causing increased inflammation and even accelerated aging. There is overwhelming evidence that endurance athletes have better oxidative defences, likely enabling them to cope better with everyday stresses, and lower so called low-grade inflammation than non-endurance trained individuals (Teixeira-Lemos et al, 2011). Also it is interesting that the tissues that are particularly subject to oxidative stress, i.e. skeletal muscle and endothelial cells, generally do not develop cancer (consequence of DNA damage) and have amazing regenerative potential. I particular muscle has the ability to renew myonuclei from the resident muscle stem cells, satellite cells and thus cope well with DNA damage. I suspect it works like that for a reason…..
Claims 5 and 6 are about the sexual hormones and function. They stem from an animal study in which rats were subjected to swimming 3 hours a day 5 days a week and found large decreases in circulating hormones and even sexual organ size (Manna et al, 2004). Unfortunately I have not been able to access the original study, so I can’t comment as qualified as I’d liked to. initially I can safely state it is done in growing rats, so one could speculate that the development of their sexual organs is not complete and they could be more susceptible to oxidative stress. Besides that there are numerous ways to perform swimming experiments with rats and I know from experience that some are quite hardcore in that they often bring the rats quite close to drowning, which could probably easily suppress hypothalamic-pituitary-gonadal axis. Another fact that may make this even more relevant is that while rats are excellent swimmers, they are not natural endurance athletes, which could stress them even more and possibly make their muscles and systemic environments more susceptible to this kind of exercise’s effects. Summarizing, I have a very hard time believing that the effects on genital size have any implications for human biology and furthermore I also have a hard time assessing what the exercise intervention used would translate to i terms of human exercise (I’m pretty sure “race across America” also messes seriously with every single organ system in the body)
The last claim, that exercise compromises immune function is also in stark contrast to the scientific consensus. There is absolutely no doubt that intense exercise acutely suppresses immune function, no matter if its endurance or resistance exercise, but there are absolutely no indications of a general impaired immune function. International Society of Exercise and Immunology (ISEI) recently published a position stand covering this field nicely (Walsh et al, 2011).
Why Is he saying these things?
At the basic level there can be only two explanations: 1) he doesn’t know any better and simply fails physiology literature, or 2) he knows these claims are false and has some kind of agenda.
If the answer i 1), I guess that’s okay. Everyone makes mistakes, but if that is the case he should do his research better prior to making statements this controversial. I do find it very hard to believe that this should be the case.
If, on the other hand it is option 2), the most obvious explanation is that his agenda is about branding through i) validating the exercise interventions he usually recommends, by saying that the alternative is dangerous, ii) he want to assume a position in opposition to that of the scientific consensus in order to establish or reinforce an “us-versus-them” attitude in his disciples, creating or reinforcing follower coherency, or iii) he’s doing it to sell supplements (or any combination of the three).
There could really be any reason or combination of reasons that Poliquin is doing things the way he is, and saying the stuff he’s saying, but no matter what it doesn’t justify saying things that are quite simply untrue. Intentional or not.
Poliquin is first and foremost a strength and then a nutrition specialist, not unlike myself and when he says that for maximal impact on health and body composition, people should focus on resistance training and high intensity (mostly anaerobic) cardio training, I agree. But I most certainly do not agree that lower intensity, endurance-type cardio is unhealthy. Even if it may cause myocardial damage to a few elite ultra endurance athletes, it is most likely that the beneficial effects on other parts of the body fully offsets this. The Ironic part is that the very few whose hearts could possibly be damaged by this kind of exercise couldn’t care less about Poliquin, whereas those who could benefit from endurance training are a lot more likely to get to know of his “warnings” and acting (poorly) from them… Put in another way, for every single person whose heart have been damaged by endurance exercise, hundreds or thousands would benefit from it (especially those people most likely to be compliant with this exercise modality), underscoring what a magnificent dick move this is on Poliquins behalf…
George, K., Spence, A., Naylor, L. H., Whyte, G. P., & Green, D. J. (2011). Cardiac adaptation to acute and chronic participation in endurance sports. Heart (British Cardiac Society), 97(24), 1999–2004. doi:10.1136/heartjnl-2011-300536
La Gerche, A., Burns, A. T., Mooney, D. J., Inder, W. J., Taylor, A. J., Bogaert, J., Macisaac, A. I., et al. (2011). Exercise-induced right ventricular dysfunction and structural remodelling in endurance athletes. Eur Heart J. doi:10.1093/eurheartj/ehr397
Kujala, U., Marti, P., Kaprio, J., Hernelahti, M., Tikkanen, H., & Sarna, S. (2003). Occurrence of Chronic Disease in Former Top-Level Athletes: Predominance of Benefits, Risks or Selection Effects? Sports Medicine, 33(8), 553–561. Adis International.
Manna, I., Jana, K., & Samanta, P. K. (2004). Intensive swimming exercise-induced oxidative stress and reproductive dysfunction in male wistar rats: protective role of alpha-tocopherol succinate. Can.J Appl Physiol, 29(2), 172–185.
Marzatico, F., Pansarasa, O., Bertorelli, L., Somenzini, L., & Valle, Della, G. (1997). Blood free radical antioxidant enzymes and lipid peroxides following long-distance and lactacidemic performances in highly trained aerobic and sprint athletes. The Journal of sports medicine and physical fitness, 37(4), 235–239.
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Skoluda, N., Dettenborn, L., Stalder, T., & Kirschbaum, C. (2011). Elevated hair cortisol concentrations in endurance athletes. Psychoneuroendocrinology. doi:10.1016/j.psyneuen.2011.09.001
Teixeira-Lemos, E., Nunes, S., Teixeira, F., & Reis, F. (2011). Regular physical exercise training assists in preventing type 2 diabetes development: focus on its antioxidant and anti-inflammatory properties. Cardiovascular diabetology, 10, 12. doi:10.1186/1475-2840-10-12
Walsh, N. P., Gleeson, M., Shephard, R. J., Gleeson, M., Woods, J. A., Bishop, N. C., Fleshner, M., et al. (2011). Position statement. Part one: Immune function and exercise. Exerc Immunol Rev, 17, 6–63.
Wilson, M., O’Hanlon, R., Prasad, S., Deighan, A., Macmillan, P., Oxborough, D., Godfrey, R., et al. (2011). Diverse patterns of myocardial fibrosis in lifelong, veteran endurance athletes. Journal of Applied Physiology, 110(6), 1622–1626. doi:10.1152/japplphysiol.01280.2010