Dear Cyclists (or other endurance athletes),
Since your heart—a muscle, like any other muscle in your body—is at the crux of cycling performance, I thought a story on a common heart condition might be helpful.
The story involves a common cardiac condition called “tachycardia-mediated cardiomyopathy.”
Now hold on a minute; don’t click away yet. Let me explain. Give science a chance.
First a translation: tachycardia means excessively fast heart rate (>120-140bpm–all the time), cardiomyopathy means disease of the heart muscle (in this case, a weakening of the heart muscle–a low ejection fraction.) As it turns out, persistently fast heart rates lead to weakening of the heart muscle–as if the high rate is poisonous.
Want to study heart failure due to a weak heart muscle in the animal lab? One model is to place a pacemaker in an animal and persistently pace the heart too fast. In a few weeks, the ventricles (pumping chambers) will weaken, and heart failure signs will ensue. A very, very common real-life manifestation of this phenomenon is the patient who unknowingly develops atrial fibrillation. The unfelt rapid heart beat progressively weakens the heart and results in heart failure symptoms. (The good news for such patients is that medical treatment often results in complete and permanent resolution.)
Other than knowing an answer in a medical jeopardy game, why is this important information for endurance athletes?
What’s your point? Going fast requires toughness of mind and body. We need the miles, and the intensity. Harden-up, will ya. Have you not heard the stories on why East Africans are such good distance runners: because they run all the time, everywhere, to school and back, for instance. Duh, we Americans don’t run enough, that’s why we are slower.”
That’s where the heart muscle story comes in. Muscles, the heart included, are indeed quite malleable. Consistently placing a load on a muscle results in an increase in mass and contractility. But the caveat is that a muscle needs time to recover and rejuvenate. Lack of rest not only disallows these favorable adaptations, it can also actually decrease performance and in extreme cases, like persistently tachycardic patients, the muscles become dysfunctional.
No, I am not saying excessive exercise will lead to heart failure, rather, I am using a common medical condition to illustrate the importance of resting an overloaded muscle, and that the well-known manifestations of over-training have a real physiologic basis.
Muscles need rest. Hard work is a good thing, but for many cross country runners, cyclists and endurance athletes, working harder at resting is more challenging than gutting out another quarter-mile repeat or hot-lap.
It has been said many times before, but bears repeating: go hard on hard days and easy on easy days. Your muscles will like this.
Good luck with that.