When is endurance training too much?
By Zach Chudy Waukesha Chiropractor, Sep 18 2014 10:00PM
This past weekend I had a chance to adjust runners after they finished marathons, half marathons, and 50K races. After seeing a lot of people in pain, I decided to do some research on safe training and recovery as well as the risk of endurance training.
Over the last several years there have been reported deaths during marathons of experienced and inexperienced runners alike. Have the risks increased?
The answer is no - the risk of sudden cardiac death (SCD) is still 1 in 100,000 people. What has changed is the number of people who are participating in these races (an increase of twentyfold of the past 30 years)! Although it’s great to see more people exercising and getting into shape, there are some risks and things to avoid.
Contrary to popular belief it is actually the younger population that is more likely to be at risk than the older population. Individuals over 40 may already be diagnosed with a disorder such as coronary artery disease and thus be more aware of their limits.
Those under 40 may never know that anything is wrong until it’s too late due to underlying conditions of the heart. Although the risk is rare (1 in 100,000) it is still a concern and is being researched more and more recently.
During training the left ventricle wall actually increases in thickness, the heart increases cardiac mass overall, and the left atrium increases in size as well. In the general population this is considered predictive of a poor cardiac outcome.
These changes are no longer thought to be harmless in athletes. Over time this dilation may result in cardiac scarring which can trigger arrhythmias and fibrillation. After a marathon 50% of runners have increased levels of biomarkers (which assess cardiac damage) and renal (kidney) dysfunctions.
However, our bodies are able to adapt to these changes when they occur in small amounts. With sufficient recovery, your body will heal itself. However, repeating training and recovery over and over again can lead to structural changes which result in fibrosis and scarring.
Another study showed aortic stiffness in marathoners which is associated with cardiovascular risk for any population. Marathoners’ higher artery calcium and plaque levels lead to decreased diastolic filling time. These issues contribute to scarring which can cause fatal arrhythmias and fibrillation.
Currently the only indicator to look for in younger runners (under 40) who might be genetically predisposed to heart problems is a very expensive cardiac MRI. In most cases a cardiac murmur may be all that shows up in physical exam (75%).
However, running is still beneficial: in moderation, it causes a 19% overall reduction in all-cause mortality. According to studies the most effective way to run is 2-5 times per week, 1 to 20 miles per week, and at a pace of 6-7 miles per hour. No benefits were seen going beyond this recommended amount and running more than these amounts can actually be worse for your health in the long run.
Some things you can do to decrease the risk of endurance training: Increase recovery time, make sure you get enough sleep, eat a healthy diet, and manage stress. After running there is an increased risk of upper respiratory tract infections, so make sure to rest, stay hydrated, and replace lost electrolytes.
A 4:1 carb to protein level is recommended for recovery for any exercise over 60-90 minutes. This ratio stimulates muscle protein synthesis at a higher level. Also, according to studies, vitamins E and C have been shown to partially prevent skeletal muscle damage caused by exhaustive exercise.
Running is still very good for you and risks are low. Don’t let these studies stop you from running - just take precautions and remember that proper rest and recovery afterwards makes all the difference.
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