Heart damage risk from excess endurance training

[on3m@n@rmy]

Not sure what to think of this finding yet, that of the possible negative health affects of extended endurance training. I'd hate to think I've been carving out an early grave.

http://www.cbc.ca/news/health/story/2012/06/01/marathon-endurance-heart.html

thoughts?

 

[QuickStepper]

One of the more frightening aspects of doing excessive endurance exercise (like a lot of the long-distance cycling I've done for more than 40 years) is that there is now evidence that this can cause scar tissue to form on the myocardium. The effects of scar tissue are not immediately apparent, but over time this can have profound effects on electrical conduction of the heart muscle.

The heart has a natural "pacemaker" in the sinus node, located in the upper right atrium. The sinus node is where the electrical impulse begins and it travels through the ion channels in the heart tissue from the top down, and it is this signal that causes the heart to contract and releax rhythmically, which enables the pumping of blood.

Over time this scar tissue (again, thought to be caused by, among other things, excessive endurance exercise) "remodels" and when this occurs, it can interrupt the electrical impulse as it travels downward toward the ventricles. When the ventricle's signal is interrupted, this can have devastating consequences, including ventricular fibrillation. When v-fib occurs, the ventricle doesn't contract, can't pump blood, and oxygen doesn't get to vital organs, muscle tissue or the brain. If CPR and defibrillation aren't rendered quickly (within a few minutes at most) the result is usually "Sudden Cardiac Death". Prior to death, it's called "Sudden Cardiac Arrest", and it is not the same thing as a heart attack (caused by blocked arteries), but rather is an electrical disturbance usually caused by some prior damage to heart muscle tissue that ultimately interferes with electrical conduction.

I know this from personal experience. This past July 10 I experienced Sudden Cardia Arrest. I have no memory of the event. One minute I was sitting at work, and my next memory is waking up in the hospital two days later. What happened was that my heart went into v-fib and I quickly collapsed and lost conciousness. Had it not been for the heroic acts of several of my co-workers who adminstered CPR for 18 minutes until the paramedics arrived and shocked me back to a normal sinus rhythm, I would be dead. I was taken to the hospital where I arrested three more times. The doctors put in an ICD (internal cardiac defibrillator) which will shock me if this ever happens again. I spent 6 days in the hospital, and then spent the rest of July recovering.

It's been almost two months since I got the ICD, and I've not had any further instances of arryhthmias, thankfully. I'm back to riding my road bike, but I have cut down on the frequency, distance and intensity of my rides. Now instead of going out and hammering 50 or 60 miles, I do about 20-25 and trhy to keep my HR low (which is easy with the beta blockers the docs prescibed). I am just happy to be alive and able to ride.

Do I think that all the long-distance and endurance cycling I did for close to 40 years (averaging close to 10K miles per year) contributed to the event? I don't know, but it certainly could have from all of the research I've done. There are no definitive answers though, and over the years I've also read studies that it's not just the intensity and distance that can cause scarring of heart tissue, but also when and where one rides. For example, there's a German study (can't find the link right now) that concluded sitting in or near traffic, or exercising during rush hour or near a highway (where diesel and auto exhaust is high) can cause heart damage, tissue scarring and increase the odds of developing coronary artery disease dramatically. Everyone I know rides either early in the morning (close to rush hour) or in the summer months in the early evening (also close to rush hour). Are those who do that becoming more healthy, or actually hurting themselves? There is some very interesting evidence that more, or riding harder, is not necessarily better.

 

[I Watch Cycling In July]

We attempted to talk about it in the doping in soccer thread, beginning with this post. http://forum.cyclingnews.com/showpost.php?p=817215&postcount=129 There is a lot of emotive and obnoxious stuff but there might be a few gems of interesting information.

Basically, risk of sudden cardiac death increases about four fold in elite endurance sports people, due to thickening in part of the heart but I can't remember the detail. It is possible to identify the majority of people at risk through thorough cardiac testing. If those at risk are prevented from becoming endurance athletes, the death rate from SCD in endurance athletes falls back to back to close to the population norm. IOW, if people are tested when young, it is possible in most cases to identify those at risk and advise lifestyle choices to remove much of the risk. It gets trickier to identify the problem once a lot of exercise induced cardiac adaption has happened, but it isn't impossible to get useful information if the cardiologist has appropriate experience.

If someone is really worried they could probably find a cardiologist with suitable experience to identify whether they are at risk, but the condition is actually quite rare. Some cardiologists advise people to organize it for their kids if they begin to take sports seriously.

 

[QuickStepper]

We attempted to talk about it in the doping in soccer thread, beginning with this post. http://forum.cyclingnews.com/showpost.php?p=817215&postcount=129 There is a lot of emotive and obnoxious stuff but there might be a few gems of interesting information.

Basically, risk of sudden cardiac death increases about four fold in elite endurance sports people, due to thickening in part of the heart but I can't remember the detail. It is possible to identify the majority of people at risk through thorough cardiac testing. If those at risk are prevented from becoming endurance athletes, the death rate from SCD in endurance athletes falls back to back to close to the population norm. IOW, if people are tested when young, it is possible in most cases to identify those at risk and advise lifestyle choices to remove much of the risk. It gets trickier to identify the problem once a lot of exercise induced cardiac adaption has happened, but it isn't impossible to get useful information if the cardiologist has appropriate experience.

If someone is really worried they could probably find a cardiologist with suitable experience to identify whether they are at risk, but the condition is actually quite rare. Some cardiologists advise people to organize it for their kids if they begin to take sports seriously.

There are certain types of cardiomyopathies that predispose people to experience Sudden Cardiac Arrest (SCA) more than others, but detecting them in all cases is not yet possible. The one definitive area where testing (mostly with EKG and cardiac ultrasound) has proven fruitful is with young adults who have hypertrophic cardiomyopathy, which is a form of premature thickening of the heart wall muscle and enlargement of the atria, ventricles, or both. Screening of young adults is now being done with greater frequency as awareness of the condition has risen with the sudden and unexpected deaths of so many young athletes, mostly basketball and football players. You don't often hear about this with young cyclists though and I think that's just because most young athletes aren't involved in the endurance side of the sport very much, and most don't recognize training for racing as a causative factor, at least not as much as they perhaps should.

In both young adults and older adults, a critical aspect of the detection can be, as you note, that some cardiomyopathies are simply hard to detect and even if detected, it's difficult to know precisely what to do about them and how much to limit exercise. Some testing can determine some of the congenital myopathies, but in otherwise healthy individuals there is often no real way to definitively determine in advance whose heart is going to become so altered by the performance of endurance exercise that they will experience the sorts of changes that will put them at risk for SCA.

The thickening of the heart muscle that occurs over time with continued and repeated strenuous endurance aerobic exercise is often what is simply referred to as "athlete's heart". The ventricle walls become thick over time in response to the activity (just like other muscles do when stressed), the atria can become enlarged (at least more so than it would be without such exercise activity), and while this may lead to more efficient pumping during the stress activity, it also over time begins to signal changes in the basic structure of the myocadium and conduction, and can lead to heart muscle tissue becoming scarred, fibrotic and eventually lead to the sorts of electrical disturbances and anomalies that I described above.

This process though can be quite slow and it can have myriad effects. SCA from v-fib caused by conduction interference from scar tissue is just one such outcome. Others are heart failure (in which the heart muscle, overly enlarged and eventually weakend, just turns into a big floppy "catchers mitt" and loses its ability over time to effeciently pump, eventually leading to fluid accumulation, high blood pressure, edema, and often death), or stiffening of the arteries of the heart (atherosclerosis) from the increased pressures (this often first manifests as simple uncontrolled high blood pressure in many people) to again, the development of scarring, fibrosis of the muscle and in general, the inability of the heart to again "remodel" when one stops performing the activity that caused the hypertrophy in the first instance.

This article from TheHeart.org provides a bit more information than the one originally cited by on3m@n@rmy, and it directly addresses the "more is sometimes less" issue when it comes to aerobic training.

 

[irongrl]

This is a concern for me, as I've been doing long distance cycling and running for almost 20 years. I'm 49 and starting to get more concerned about the impact of my habits on my heart. According to the second article posted, the damage is only thought to occur with running over 25 miles a week. They said that "light" cycling and walking of any amount was ok. I have backed off quite a bit so I think I will be ok. Also, I did a heart and vascular screening last year and everything was good.

 

[Frank222]

Not just endurance training but any any type of exercise is bad in excess. Everything demands a good balance, so there should be a good balance in exercise and diet plan. Excess weight lifting causes DOMS and some other muscles issues.

 

[del1962]

If you can run a max of 25 miles per week without doing damage, this rules out the sort of training required to run a marathon

 

[longworn]

Cardiac damage possible from Endurance sport - base level fitness vital

In reply to thread, the evidence is endurance sport does harm the heart, its just the repair process which really causes problems. Basically it causes scarring and that scarring can result in atrial fibrillation. Actually doing a Deca Ironman and I hope to put together a study to prove it http://decaironman-training.com/201...te-cardiac-damage-from-ultra-endurance-sport/ Exploring funding options, hard to do very PT particularly with training!