Endurance Exercise: How Much is Too Much?

     To all those who dread spending countless hours in the gym, I've got great news for you: less is more. This is not permission to skip the gym or leave without completing a workout. More often than not, the average American needs to workout more. The benefits of exercise are well-known: your heart pumps more effectively; the amount of oxygen in your blood increases; body's immune system is activated; and the number of endorphin's increase which elevate your mood. But just like everything else in life, there is a tipping point. That point is not defined and is different for everyone but when your training sessions gets into 60+ minutes, you should be cautious. Just because a little bit of something is good, doesn't mean a lot of it is better.

     Excessive exercise can backfire on you for a variety of reasons. After prolonged bouts of training, your body will run out of fuel sources. When this occurs, your body enters a catabolic state where it will begin breaking down muscle tissue and using it as energy. One other contributor to putting your body in a catabolic state is the stress hormone cortisol. As your exercise session increases, so too does the release of cortisol. Both of these factors have a negative effect on your lean body mass. This is why some endurance athletes are incredibly thin but also have a stomach pouch or no muscular definition. Along with negatively effecting your lean body mass, you may also develop microscopic tears that only heal with rest and if you do not recover properly, it will begin to weaken your immune system. So, if you are working out like crazy and are always hurting or getting sick far too often, it is highly likely that you aren't recovering properly. However, the most serious risk can be damaging your most important muscle: the heart.

     High endurance training puts extraordinary stress on your heart. The heart is a muscle and like all other muscles, if it is worked too hard, damage can be done. Some stress is good, but too much stress can lead to serious damage and in some cases death. Need proof? These eight studies may stop you right in your tracks!

1. According to a study presented at the Canadian Cardiovascular Congress 2010 in Montreal, regular exercise reduces cardiovascular risk by a factor of two or three, but the extended vigorous exercise performed during a marathon raises your cardiac risk seven-fold!
2. In a 2011 study published in the Journal of Applied Physiology, researchers recruited a group of extremely fit older men, all members of the 100 Marathon club (having completed a minimum of 100 marathons). Half of the men showed heart muscle scarring as a result of their endurance running—specifically, the half who had trained the longest and hardest. If running marathons provided cardiovascular benefit, this group would have had the healthiest hearts!
3. A 2011 rat study published in the journal Circulation was designed to mimic the strenuous daily exercise load of serious marathoners over the course of 10 years. All the rats had normal, healthy hearts at the outset of the study, but by the end, most of them had developed "diffuse scarring and some structural changes, similar to the changes seen in the human endurance athletes."
4. A 2012 study in the European Heart Journal found that long-term endurance athletes suffer from diminished function of the right ventricle of the heart and increased cardiac enzymes (markers for heart injury) after endurance racing, which may activate platelet formation and clotting. Twelve percent of the athletes had detectable scar tissue on their heart muscle one week post-race.
5. A 2010 study presented by the American College of Cardiology showed that endurance runners have more calcified plaque in their arteries (which also increases stroke and dementia risk) than those who are not endurance athletes.
6. A 2011 German study revealed a very high incidence of carotid and peripheral atherosclerosis among male marathon runners.
7. A 2006 study screened 60 non-elite participants of the 2004 and 2005 Boston Marathons, using echocardiography and serum biomarkers. Researchers found decreased right ventricular systolic function in the runners, caused by an increase in inflammation and a decrease in blood flow.
8. Research by Dr. Arthur Siegel, director of Internal Medicine at Harvard's McLean Hospital, also found that long-distance running leads to high levels of inflammation that may trigger cardiac events.

     At rest, your heart pumps out about five quarts of blood per minute. While running, that number goes up to 25-30 quarts per minute. The heart is not designed for this type of volume overload for longs periods of time. This increase in volume stretches the walls of your heart muscle and literally breaks fibers apart. This can lead to scarring. Combine that with how some training plans are for endurance races, and you are constantly overloading the heart on a regular basis. The results of this study show us that it can be assumed that most endurance athletes do not give their heart adequate time to recover. With inadequate rest, the body is in a "post-workout" state and these athletes will have cardiac fatigue. The fatigue is a precursor for heart arrhythmia which can lead to full cardiac arrest. This is why 50 percent of marathon deaths occur in the last mile of the race. The chronic stress is too much and the body cannot withstand it. Even the very first "marathoner", Greek messenger Phidippides, couldn't take the stress. After covering 175 miles in two days he suddenly dropped dead.

     Now, keep in mind I am talking about high-endurance events. Do not give up on running and do not throw those running shoes away just yet. Keep your miles to around 20 per week, spread them out over 3-5 days, keep your heart rate steady and allow yourself adequate time to recover. Most important, listen to your body. Do not ignore the signals of distress and get rid of the "no pain, no gain" mindset. Your heart will appreciate it!

This blog is a summary. For more information, check out the following article:
http://fitness.mercola.com/sites/fitness/archive/2013/08/23/extreme-endurance-exercise.aspx?e_cid=20130823Z1_PRNL_art_1&utm_source=prmrnl&utm_medium=email&utm_content=art1&utm_campaign=20130823Z1.

Hope you enjoyed!
Chris Fluck