For years, exercise physiologists thought that muscle fatigue was a result of lactic acid. Feel the burn. Now they have A New Explanation of Muscle Fatigue:
Muscle contraction and relaxation are controlled by the release and storage of calcium ions within muscle fibers. Scientists at Columbia University say thtat muscle fatigue, largely misunderstood for decades, is caused by calcium leaking into muscle cells.
Muscle Contraction
Calcium ions are released into the cell, causing filaments in the muscle fiber to contract.
Muscle Relaxation
Calcium ions are pumped into storage, allowing the muscle filaments to relax.
The discovery came while looking at heart disease:
As the damaged heart tries to deal with the body’s demands for blood, the nervous system floods the heart with the fight or flight hormones, epinephrine and norepinephrine, that make the heart muscle cells contract harder.The intensified contractions, Dr. Marks and his colleagues discovered, occurred because the hormones caused calcium to be released into the heart muscle cells’ channels.
But eventually the epinephrine and norepinephrine cannot stimulate the heart enough to meet the demands for blood. The brain responds by releasing more and more of those fight or flight hormones until it is releasing them all the time. At that point, the calcium channels in heart muscle are overstimulated and start to leak.
What can be done about that?
When they understood the mechanisms, the researchers developed a class of experimental drugs that block the leaks in calcium channels in the heart muscle. The drugs were originally created to block cells’ calcium channels, a way of lowering blood pressure.Dr. Marks and his colleagues altered the drugs to make them less toxic and to rid them of their ability to block calcium channels. They were left with drugs that stopped calcium leaks. The investigators called the drugs rycals, because they attach to the ryanodine receptor/calcium release channel in heart muscle cells. The investigators tested rycals in mice and found that they could prevent heart failure and arrhythmias in the animals. Columbia obtained a patent for the drugs and licensed them to a start-up company, Armgo Pharma of New York. Dr. Marks is a consultant to the company.
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“If you go to the hospital and ask heart failure patients what is bothering them, they don’t say their heart is weak,” Dr. Marks said. “They say they are weak.”So he and his colleagues looked at making mice exercise to exhaustion, swimming and then running on a treadmill. The calcium channels in their skeletal muscles became leaky, the investigators found. And when they gave the mice their experimental drug, the animals could run 10 to 20 percent longer.
It looks like it works on human cyclists too — so I have to assume human cyclists will be using it outside the lab.