Gabe Mirkin, M.D.
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. World-class
competitive bicycle racers ride at close to their maximum heart
rate for five to seven hours a day. Many researchers have been
concerned that this very hard riding would damage their heart
muscle as well as their skeletal muscles. A study from Freiburg University in Germany
shows that hard exercise does not damage a healthy heart.
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 (Medicine and
Science in Sports and Exercise, October 2003). Post exercise
electrocardiograms and echocardiograms were normal as were
blood levels of heart-specific enzymes, creatine kinase, 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 may not 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.
March 1, 2006