In my continued effort to take a deeper look at the research surrounding the potential long-term health implications of chronic endurance exercise, I decided to focus this month on ultra-endurance running. Before diving into this topic, I want to be clear that exercise of all types confers incredible health benefits. When I discuss my interest in the potential negative long-term implications of endurance exercise, this is limited in scope to chronic, high volumes of endurance exercise that has gained more attention for its relationship to a small, elevated health risks. In particular, high levels of endurance exercise and sport participation has, in some research, demonstrated a very small increased risk of cardiovascular health concerns.
Naturally, as both an endurance athlete and coach, I figured I should be more well-versed in this emerging area of research so that I am aware of any risks that might be present among endurance athletes participating in high loads of training and/or racing for long periods of time. This is, importantly, an emerging area of research. This means that most of the evidence we have fuels more questions than answers. Nonetheless, I have found it interesting to look at, and hopefully you will find it interesting to learn more about as well.
With all of this said, let’s look at a recent paper that focused on discussing potential long-term health problems associated with ultra-endurance running.
Are there risks associated with ultra-endurance running?
In 2022, Scheer and colleagues (1) published a narrative review in which they aimed to discuss potential long-term health risks associated specifically with ultra-endurance running (i.e., running longer than 26.2 miles or ~6 hours). The authors looked at relevant research literature, some of it in ultra-endurance runners and some of it in other endurance athlete populations and non-athlete populations, and categorized possible long-term health risks into various categories. These categories were broken down by key organ systems, including cardiovascular, respiratory, musculoskeletal, renal, immunological, gastrointestinal, neurological, and integumentary (i.e., skin/dermatological) systems.
I will spend time focusing primarily on the highest risk categories where there is some evidence indicating there is some concern to be considered. However, see Table 1 directly from this paper below in which the authors provide a summary of key findings across each organ system.
Of all the possible concerns discussed, many of them could reasonably be mitigated or outright eliminated to some extent with proper training load management and adequate rest and recovery habits. For example, overtraining combined with improper recovery is known to have deleterious effects on the immune system. This is true for any athletic population, not just ultra-endurance runners. However, avoiding overtraining and ensuring proper rest and recovery practices around training and racing can practically eliminate the risk of possible immunological concerns across all athletic populations. I want to focus the rest of my discussion on specific concerns that might be unique to ultra-endurance trail runners or specific risks that might be present despite proper training load management and recovery practices.
The number one category that stood out to me was the possibility of elevated cardiovascular health impacts from ultra-endurance running. This is where most of this emerging area of research focuses across chronic endurance participation more broadly, and there is some mounting evidence showing there may be an increased risk of cardiovascular health complications with high levels of endurance sports participation, of which ultra-endurance runners would certainly align. These risks include potential damage and scarring to the heart walls and chambers, inflammation of the heart, higher coronary artery calcification scores, and more. However, the risk of experiencing a deadly or serious cardiovascular incident in endurance athletes is still very small. There may also be some genetic predispositions that make some athletes more likely to experience a cardiovascular health problem with chronic endurance exercise. More research is needed, but this is my biggest interest area personally as there does seem to be consistent evidence demonstrating a small risk among those that engage in high levels of endurance exercise for many years.
The next category that stood out to me, and that is possibly unique to ultra-endurance running, is that of long-term respiratory concerns. Recurring exercise-induced bronchoconstriction from exercising for long durations or at high-intensities in cold, dry air or in poor air quality conditions may have some adverse effects on overall respiratory health. However, more research is needed related to this topic as this is mostly speculative at this point. Ultra-distance runners, however, are more likely than many endurance athletes to be exercising in dryer, colder conditions as well as conditions in which there is poor air quality depending on the geographical location that one trains and races in. Therefore, it makes some sense to consider possible respiratory effects of repeated exposure to training and racing conditions if they take place in certain conditions that place stress and strain on this organ system. For example, authors in the paper outlined above mentioned a scenario in which exercise-induced bronchoconstriction (EIB; i.e., constriction of the cells of the lungs in which gas exchange between the lungs and blood stream occurs) that can take place after prolonged endurance exercise in cold, dry, or poor air quality environments. The repeated occurrence of this EIB may have some long-term consequences on respiratory health that need further exploration.
What to do about the risks that might be present?
In sum, there might be some small risks unique to endurance athletes more globally when it comes to cardiovascular outcomes and possibly respiratory outcomes depending on the environment that one chooses to train and race in. This risk, however, is small and there is still much more research needed before any firm conclusions can be made.
Personally, I consider the cardiovascular-related and pulmonary-related risks to be something to take seriously. The best way to mitigate these risks, in my opinion and with the limited research we have available, could possibly come down to just being smart in the way that you engage with training and racing over time. Of course, there is the possibility of genetic components that cannot be altered and that might present an elevated risk of certain long-term health implications. The remaining risk might be best managed through smart approaches to training and racing, but there really isn’t any firm research here to back up this assertion.
Managing training load and intensity well over time and being strategic about exercising in certain environmental conditions would be my top recommendations if I were to provide any. By managing training load intelligently and putting a constant emphasis on proper recovery, athletes can minimize the deleterious impact that chronic overloading and/or under-recovering may have on cardiovascular health. Furthermore, by avoiding exercise in poor air quality conditions (e.g., in areas subjected to wildfire smoke, or in more populated areas when air quality is poor) and just being aware of not over-doing exercise in cold and dry conditions on a regular basis, one might be able to avoid some deleterious consequences on long-term pulmonary health as well.
Endurance exercise, even at high levels, confers incredible health benefits. Even elite-level endurance athletes when compared to the general population have much better long-term health outcomes and a much lower risk of all-cause mortality. So, don’t take any of this discussion herein as a recommendation to stop endurance training and racing. However, take the information I have laid out as something to be cognizant of and to keep up to date with as newer research emerges. Be aware of any potential risks and seek to mitigate these risks as more and more answers, and hopefully solutions, come to be available.
1. Scheer V, Tiller NB, Doutreleau S, Khodaee M, Knechtle B, Pasternak A, Rojas-Valverde D. Potential long-term health problems associated with ultra-endurance running: a narrative review. Sports Medicine. 2022 Apr;52(4):725-40.
Happy training and racing!
-Ryan Eckert, MS, CSCS
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