A study from Freiburg University in Germany shows that hard exercise does not damage the heart. To improve for athletic competition, all athletes must suffer skeletal muscle damage. Without this damage their muscles will not grow and they will not become stronger. So on one day, they exercise very intensely by lifting very heavy weights, running very fast, or competing on the basketball court very intensely. They know that they have damaged their muscles with hard exercise because their muscles feel sore on the next day. As the muscles heal, they produce growth hormones that help the muscles to grow larger and stronger. Athletes can tell when their muscles have healed because the soreness goes away and the athlete then takes another hard workout to damage his muscle again.
World-class competitive bicycle racers ride at close to their maximum heart rate. for 5 to 7 hours a day. Many researchers have been concerned that this very hard riding would damage their heart muscle as well as their skeletal muscles. They know that when muscles are damaged, they release enzymes into the blood stream. This study shows that the heart muscle is not damaged the way that skeletal muscles are. Post exercise electrocardiograms and echocardiograms were normal as were blood levels of heart-specific enzymes, creatine kinase and creatine kinase MB, and myoglobin. However, older bicycle racers did have a rise in another enzyme, brain natriuretic peptide, that is associated with heart function. The authors felt that this shows that older athletes cannot adequately empty their heart's ventricles during the diastolic relaxation phase and the increased pressure stretches the heart muscles to raise blood levels of this hormone.
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