Being in a scientific field, we know that exercise is good… and that we should probably exercise. It betters our mood, it decreases stress, I mean the list goes on forever. What if I told you that there are actually negative side effects to exercise? I mean markers that could indicate a recent myocardial infarction (MI) or changes in some values that are noticed in… well people that don’t exercise?
There is one key factor to the production of these negative markers, and it has to do with the amount of strain from the exercise completed. For the sake of this blog post, we will focus on post-marathon measurements. A marathon is a 26.2-mile race that takes an unbelievable amount of aerobic fitness and mental drive to complete. The fastest ever recorded in a competition setting was 2:01:09 by Eliud Kipchoge from Kenya in Berlin this year (Douglas, 2022). This equates to an average mile of 4:37!
After a marathon, Troponin I can be elevated from a baseline measurement of 0.02 ng/mL to 0.2 ng/mL (Trivax, 2010). For reference, an intermediate value would be anything between 0.06-1.2 ng/ml and anything higher would be indicative of an MI. Troponin I levels are markers used to identify damage to the heart, so any value is concerning, but we see measurements under what is expected after extreme damage. Furthermore, right ventricular end-systolic (RVESV) measurements are elevated (10 mL/m^2) post-race (Trivax, 2010), but left ventricle end-systolic measurements were not significant enough to show change. How can this happen? The researchers attributed the change in the right ventricle due to the dilation of the chamber. This makes sense as dilation is seen due to different mechanisms in those with heart failure (the stretch of muscles). Both situations lead to a greater ESV, but the marathon runners are able to return to baseline.
Another study mentioned the long-term effects of aerobic stress on the heart and indicated that endurance athletes are four times more likely to develop atrial arrhythmias later in life (Mont et al., 2009). That is a 300% increase! This is only a relative risk though, so to see a proper correlation, we would need absolute risk. It also turns out that atrial arrhythmias are not very fatal, but require medical attention.
In conclusion, this isn’t an excuse to skip endurance exercise, but more of a suggestion to not be the world’s fastest marathon runner…
Douglas, Scott. (2022). These are the world’s fastest marathoners. Runnersworld.
Accessed from https://www.runnersworld.com/races-places/a20823734/these-are-the -worlds-fastest-marathoners-and-marathon-courses/.
Mont, L., Elousa, R., Brugada, J. (2009) Endurance sport practice as a risk factor for atrial
fibrillation and atrial flutter. Europace 11: 11-17.
Trivax, J. E., Franklin, B. A., Goldstein, J. A., Chinnaiyan, K. M., Gallagher, M. J., deJong, A. T.,
Colar, J. M., Haines, D. E., & McCullough, P. A. (2010). Acute cardiac effects of marathon running. Journal of applied physiology (Bethesda, Md. : 1985), 108(5), 1148–1153. https://doi.org/10.1152/japplphysiol.01151.2009
This was a very interesting post and surprising in it's conclusion! It actually reminded me of the very shocking, sudden death of my friend's father. He was considered extremely healthy and participated in several Ironman triathlons, but he passed away of a sudden myocardial event. A research article I found postulated that in extreme endurance athletes, recurrent myocardial injury and repair may lead to myocardial scarring, especially in the atria, interventricular septum, and right ventricle. This may be the reason why endurance athletes develop atrial and ventricular arrhythmias. Additionally, they found sustained, high intensity endurance exercise to be associated with large artery wall stiffening and coronary artery calcification! If you are an endurance athlete with a congenital heart defect, the addition of an arrhythmia could be fatal. Physicians may want to consider creating guidelines for how much is too much in endurance athletes.
ReplyDeletePatil, H. R., O’Keefe, J. H., Lavie, C. J., Magalski, A., Vogel, R. A., & McCullough, P. A. (2012). Cardiovascular Damage Resulting from Chronic Excessive Endurance Exercise. Missouri Medicine, 109(4), 312–321.
Triathlete.com. (2014, February 3). From The Heart: A Former Ironman Pro’s Story Of Heart Risks For Athletes. Triathlete. https://www.triathlete.com/culture/from-the-heart/