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Running On Empty | Muscle & Body Magazine

Too much cardio can mess up your whole program. Here’s how to avoid it.

Last month, I spoke of overreach-ing and overtraining and the potential negative effects the two can have on the body. This month, I’d like to delve deeper into the subject and address the potential adverse effects of excessive cardiovascular exercise.

Physical activity is important—that goes without saying. In fact, “as little as 15 minutes per day confers substantial health benefits.” With your doctor’s permission, I would recommend physical activity last longer than 15 minutes, but it is important to know your limitations. There are athletes out there who, through “overmotivation,” have actually become addicts to their daily endurance routines.

The Danger Zone
In an animal study performed through the Mayo Clinic, it was found that “daily excessive, strenuous, uninterrupted running replicated the adverse cardiac structural remodeling and proarrhythmia substrate noted in observational studies of extreme endurance athletes.” These findings back up claims that high-endurance activity, such as marathon running, professional long-distance cycling, rowing or swimming, may cause cardiac fibrosis, diastolic (bottom number of blood pressure) dysfunction and increased susceptibility to atrial and ventricular arrhythmias (irregular heartbeat) in some individuals. To put it in more simple terms, excessive high-endurance activity can lead to negative abnormalities in the heart.

Affected athletes usually “develop cardiac adaptations including enlarged [left and right ventricle] volumes, increased [left ventricle] wall thickness and cardiac mass, and increased left atrial size, according to research.” In the general population, these adaptations in the heart are “associated with poor cardiac prognosis,” however, they are deemed “typical” in highly trained athletes. In fact, it has been found that the cardiac dimensions of these athletes “do not completely regress to normal levels even several years after the athlete has retired from competition and heavy [exercise training].”

This is not a threat by any means to all individuals who consider themselves high-endurance athletes. Carl “Chip” Lavie, MD, medical director of Cardiac Rehabilitation and Preventive Cardiology at Ochsner Clinical School in New Orleans, states, “We are not trying to scare athletes from participating in these extreme endurance events, but it is important that the risk is appreciated, especially for older athletes (e.g., age 50) and when athletes are participating at numerous long events yearly.”

Reducing Risk Of Endurance Overload
Indeed, these risks do need to be appreciated, as these abnormalities have been shown to increase over a number of years. They have even been suggested to “predispose [individuals] to serious arrhythmias such as atrial fibrillation (irregular heartbeat) and/or ventricular arrhythmias.” The good news here is that since these abnormalities do happen over a period of years, they can be prevented with careful moderation of your overall heart health.

High-endurance cyclists and marathon runners are among the most at risk for abnormalities in the heart due to the stress they endure on a constant basis. Not only do these athletes perform in some of the highest-endurance sporting events, but they also train for these events months in advance at almost equal endurance levels.

Lavie states, “With extreme exercise events, many athletes develop some evidence of cardiac dysfunction release of troponin and CPK (creatine phosphokinase that is released in heart attack), release of BNP (basic natriuretic peptide that is released with heart failure), and dilation of heart chambers and weakening of cardiac contraction.” He continues, “Although these abnormalities seem to resolve over the next several days, there is concern that some develop scarring of the heart that can lead to serious rhythm disturbances and even death.”

It’s not all bad for runners, however. A “lower dose” runner is one who runs fewer miles, less often and at slower speeds. Imagine if you will a light jog around the park: It’s enough to break a sweat, but not so exhausting that the body collapses. These lower-dose runners have been shown to have a “markedly lower mortality rate than nonrunners.”

When an athlete starts to break out of lower dose and into higher dose, say rigorous training for months for a triathlon, increased heart risk becomes a concern. Lavie’s research indicates, “Although high-dose running does not increase risk over nonrunners, more running seems to be associated with some loss in the benefits noted with lower-dose running.”

The purpose of this article is not to scare anyone into cutting back on their training or overall exercise, but merely a warning that you can, in fact, overdo it. Your body wants to exercise, and the benefits can be seen physically and mentally, but it’s important to recognize that too much of a good thing can be a bad thing. While your body wants to exercise, it also wants to recover. To figure out where you fall in the amount of stress your body can handle, The American College of Sports and Medicine suggests:

  • At least 150 minutes per week of moderate exercise training, or 75 minutes per week of vigorous exercise training in the general adult population.

  • Larger doses of exercise training may be necessary in some groups, such as those with or at risk for coronary heart disease. ACSM recommends 30–60 minutes daily.

  • Adults trying to prevent excess weight gain or obesity should include 45–60 minutes daily.

  • Formerly obese people trying to prevent weight re-gain should include 60–90 minutes daily.

    Now that you have the proper knowledge, you can determine your own exercise training routines, and how they apply to your goals. As always, I recommend you seek medical help to make sure you are healthy enough for physical activity before beginning any new exercise routine.


    Link: Running On Empty | Muscle & Body Magazine.