From: Andy Soos, ENN
Published September 9, 2011 11:21 AM

Too Much Exercise

Here is something for all those arm chair athletes in the world. Endurance athletes who train and race frequently may experience a high rate of unusual heart rhythms called arrhythmia, found a new study on cross-country skiers. Arrhythmia, which are often harmless, can sometimes lead to strokes and other serious problems. Experts remain unsure what to make of the results. Exercise is known to prolong lifespan and to improve all sorts of measures of health, including the heart. Still, the study suggests there may be a point at which a lot of training becomes too much. At the very least, serious athletes should be aware of the potential for their hearts to behave strangely.


People who are exercising a lot should probably learn how to identify the symptoms of atrial fibrillation and seek counseling if they get it," said Johan Sundström, a cardiovascular epidemiologist at Uppsala University. Irregular pulse, shortness of breath or excessive fatigue are a few symptoms.

Exercise can be both good and bad. Exercise is a stressor and the stresses of exercise have a catabolic effect on the body—contractile proteins within muscles are consumed for energy, carbohydrates and fats are similarly consumed and connective tissues are stressed and can form micro-tears[citation needed]. However, given adequate nutrition and sufficient rest to avoid overtraining, the body's reaction to this stimulus is to adapt and replete tissues at a higher level than that existing before exercising[citation needed]. The results are all the training effects of regular exercise: increased muscular strength, endurance, bone density, and connective tissue toughness.

Too much exercise can be harmful. Without proper rest, the chance of stroke or other circulation problems increases, and muscle tissue may develop slowly. Extremely intense, long-term cardiovascular exercise, as can be seen in athletes who train for multiple marathons, has been associated with scarring of the heart and heart rhythm abnormalities.

Inappropriate exercise can do more harm than good, with the definition of "inappropriate" varying according to the individual. For many activities, especially running and cycling, there are significant injuries that occur with poorly regimented exercise schedules. Injuries from accidents also remain a major concern, whereas the effects of increased exposure to air pollution seem only a minor concern.

Sundström emphasized that exercise is essential for overall health and that the vast majority of people would do well to get more of it, not less.

Exercise has long been associated with a boost in health, including lower risks of heart disease. Heavy training can change the structure of the heart, making it bigger and adding extra connective tissue.

Those adaptations help the heart pump blood more efficiently. But some small studies have also shown evidence of higher rates of arrhythmia in serious athletes, opening up lots of questions.

In the biggest study yet on the subject, Sundström and colleagues studied participants of the Vasaloppet, an annual cross-country ski race in Sweden that covers 90 kilometers (56 miles). Each year, the race attracts about 15,000 participants, who range from casual skiers to extremely dedicated athletes.

Previous research has shown that people who ski the Vasaloppet are healthier than the general population and have a mortality rate that is half that of less athletic people. Still, because the race includes such a wide range of athletes, it also offered a good opportunity to study the effects of extreme athleticism on arrhythmias.

To investigate, the researchers looked at data from a decade's worth of races. They rated the skiers' fitness level based on how close they finished to the winning time and how many times they had previously competed in the race. Then they looked at national health records to see how often participants ended up in the hospital for arrhythmia problems.

People who had done seven or more Vasaloppets were nearly 30 percent more likely to end up seeking help for arrhythmias compared to people who had only done the race once, the researchers reported last week at a meeting of the European Society of Cardiology in Paris.

The link between fitness and arrhythmias were strongest for athletes who were younger than 45. And the vast majority of arrhythmias fell into two groups: Atrial fibrillation -- a fast, irregular rhythm, and bradyarrhythmias, a particularly slow rhythm. Neither type is among the most dangerous.

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