April 15, 2013
The following is a guest post by my friend and fellow triathlete Armi Legge…leave your questions, comments and feedback below the article. This post was released the day before the Boston Marathon tragedies, and was not meant in any way to coincide with those unfortunate events.
If you’re an endurance athlete, you’ve probably seen articles claiming that your favorite sport is secretly killing you.
Do a Google search for “endurance exercise heart damage,” and you’ll find about 2,530,000 results, and countless articles that may make you think twice about your next workout.
Without getting into obsessive detail about every study on this topic, it’s safe to say the dangers of endurance sports are overblown.
That said, there are still risks that long-term endurance exercise could cause heart problems in some athletes. The risks may also be higher for athletes who are pushing the limits of performance, trying to maximize their results through more intense training.
Well-trained endurance athletes may actually have a higher risk of heart damage, since they can push themselves harder for longer (i.e. they have more endurance).(1)
There is no direct research on how to protect your heart from endurance exercise (largely because most research indicates it’s only an issue for a small minority of athletes).(2,3) However, studies have given us some clues as to how we can minimize the risks of endurance sports damaging our hearts.
Here's exactly what you need to know…
Protect Your Heart from Extreme Endurance Exercise in 6 Simple Steps
None of these solutions have been tested in randomized controlled trials, and they will not guarantee that exercise won’t damage your heart. That said, these are the most practical, simple steps that are based on the best available evidence.
1. Plan Adequate Rest
Researchers think that if “myocardial injury” (heart damage), sometimes occurs during endurance exercise, it’s similar to a training injury. The cause may also be similar — doing too much, too soon.(4-7)
Like other muscles, your heart is fatigued after a workout and needs time to recover.(8-11)In general, the harder and longer the workout, the more time it takes for heart function to return to normal.
There’s no data measuring this directly, but it’s likely your heart fatigues at a similar rate as your muscles. The demands on your heart during exercise are mostly proportional to how hard your muscles are working.
Basically, once your muscles are recovered, your heart probably is too.
The best way to know if your heart is recovered is to get an echocardiogram or an MRI, but this probably isn’t necessary. If you’re muscles are sore and fatigued, and you feel lethargic and unmotivated, your heart is probably not completely recovered. If you feel great, your heart is probably ready for another hard workout.
Here are a few tips to make sure your heart is recovering from your endurance workouts:
- Plan and periodize your season, so you can gradually increase your volume and intensity.
- Insert recovery weeks throughout your season where you decrease the volume and intensity for a few days. This helps shake off any lasting fatigue before the next series of workouts.
- Don’t destroy yourself every day in training. It’s not necessary, productive, or healthy.
- When in doubt, train less rather than more.
2. Don’t Train When You’re Sick
If you have a serious infection, don’t train.
Exercise tends to improve immune function over time, but too much training can have the opposite effect.(12-15)If you overtrain or overreach too often, you may increase your risk of developing myocarditits – a heart infection.
About 90% of people will eventually catch one of the same viruses that causes myocarditis, yet it rarely infects the heart.(16) If you’re overtraining, the chances of the disease progressing to your heart are probably higher.
Other seemingly less severe diseases like the flu can also increase the risk of myocarditis.(17)
“It is possible that this may be severe enough to cause permanent heart damage but yet the person does not feel too unwell at the time,” writes Dr. Andre La Gerche, the author of several papers on this topic.
“It is also possible that athletes are at greater risk of this because there is some evidence that exercise can compound the effects of ‘myocarditis’ and athletes will often train through anything,” continues Dr. La Gerche.
It’s still not clear if exercise causes immune function to drop.(18)Even if it does, it’s not clear if this increases your risk of developing myocarditis in particular. Only one study found a high rate of myocarditis in athletes, but it’s plausible overtraining may have contributed.(19)
In any case, if you’re already sick, hard training is probably not going to help you recover from an infection faster.(20,21)
It’s probably safe to push through minor illnesses like a cold. However, more serious infections may pose a greater risk to your heart.
3. Be Patient
Endurance athletes are ambitious people. We like to go longer, faster, and harder, often sooner than we should.
It’s not uncommon for athletes to race a marathon or Ironman after a year or two of training.
This probably isn’t the best idea in terms of heart health. It takes years of consistent training to prepare your heart for something like an ironman, half-ironman, or even a marathon. It takes time for your heart to adapt and grow larger, stronger, and more efficient.(22,23)
One study also found that better trained athletes’ hearts had a smaller rise in markers of heart stress after extreme exercise (though not many studies have looked at this relationship).(24) Most studies have also found that the hearts of athletes who train more don’t get as fatigued after exercise.(25)
That said, most recreational athletes may not be able to push themselves as hard or long as more experienced ones, which might reduce the risks. If you’re determined to start long races (2+ hours) in your first few years of training, try to finish, rather than compete.
4. Be Specific with Your Training
Your heart adapts specifically to the kind of exercise you do most.(26-28)
Similar sports tend to produce more similar changes, but they’re still slightly different. Runners and cyclists often have much larger hearts than non-athletes, but there are still subtle differences in the thickness of the heart walls and shape of the chambers.(29,30)
There hasn’t been any research on whether or not an athlete with a “swimmer’s heart” is more likely to suffer heart damage if they suddenly start running marathons. They probably aren’t.
That said, an athlete whose heart is well adapted to one sport is probably not fully prepared for the cardiovascular demands of another. If you want to do everything you can to minimize the chances that endurance exercise might damage your heart, train your heart for your sport.
If you want your heart to be ready for a marathon, lifting weights won’t cut it. You need to run — a lot.*
*Note from yours truly – I don't necessarily agree with Armi about needing to run a lot IF you are using HIIT.
5. Listen to Your Body
Endurance athletes are good at ignoring pain, fatigue, and discomfort.
When it comes to the health of your heart, this isn’t always good.
If you ever experience any of the following symptoms during or after exercise, see a doctor as soon as possible. These are often signs of heart disease.(31-33)
- Chest pain (especially on the left side).
- Dyspnea (the inability to catch your breath, even at a moderate to low effort).
- Unexplained nausea and/or dizziness.
- Extreme fatigue or lethargy despite being well rested.
These symptoms can be caused by things other than heart disease, so don’t freak out if they happen to you. That said, it’s best to see a doctor to be safe.
6. Get Your Heart Tested
If you’re really concerned about endurance exercise damaging your heart, it’s a good idea to get a check-up, or more thorough testing in some cases.
There’s still ongoing debate about whether or not athletes should get a detailed series of heart tests before they start exercising, especially if they don’t have any symptoms.(34-39)That said, most experts think it’s a good idea to at least get an electrocardiogram (ECG) and basic examination if you can afford it.(40-48)
If you’re over the age of 50, it may also be a good idea to get a coronary calcium scan to see how much, if any, plaque is in your arteries.(49,50) Some data suggests that endurance athletes (specifically, marathon runners), may have more than you’d normally expect for otherwise healthy athletes.(51)
None of these tests are 100% foolproof, and it’s still possible to have heart problems despite excellent test results.(52,53) It’s also important to give your doctor a detailed medical history so they can help you decide how much exercise is safe for your heart.*
*In addition to what Armi recommends, I'd also seriously consider checking out variables such as inflammatory markers (i.e. C-Reactive Protein), potassium and magnesium levels, etc. Check out the article “How To Test Your Body“.
Summary: Exercise Sensible Caution when it Comes to “Cardio” and Your Heart
There are real risks when it comes to endurance exercise and your heart. They’re smaller than many people would have you believe, but they do exist.
If you’ve been adhering to these tips, the chances that your training may damage your heart, or has damaged your heart, are slim.
There aren’t nearly enough studies to say definitely how likely it is that endurance exercise might damage your heart, or how to reduce these risks. Luckily, there’s enough research to develop a few educated guesses on how you can keep “cardio” from damaging your heart.
You can find more articles on whether or not endurance sports are bad for you on Imprüvism.com. Here’s a good place to start.
Disclosures: I am a long time endurance athlete and currently compete on an elite triathlon team. I am willing to accept that excessive endurance exercise contributes to heart disease if the evidence supports that conclusion, but I also admit a certain level of bias in that I hope it does not. I am also not a doctor, and this is not medical advice.
Questions, comments or feedback? Leave them below.
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