A Columbia University team found that fatigue, following strenuous exercise is caused by calcium leaking inside muscle cells. The calcium, which leaks continuously inside the muscle cells, weakens the force produced by the muscle. It also stimulates a protein-digesting enzyme that damages the muscle fibers.
The new information could explain what saps the energy from patients with heart failure and help to improve ways of treating congestive heart failure, a major killer-disease world over.
"The study does not mean exercise is bad for you," says the study's senior author, Andrew Marks, M.D., chair of the Department of Physiology and Cellular Biophysics, and director of the Clyde and Helen Wu Center for Molecular Cardiology at Columbia University Medical Center.
"People with chronic heart failure are subject to this same kind of muscle leak and damage constantly even without doing any exercise," Marks says. "One of these patients' most debilitating symptoms is muscle weakness and fatigue, which can be so bad they can't get out of bed, brush their teeth, or feed themselves."
Fatigue in athletes was previously attributed to the accumulation of lactic acid in the muscles. Also the debilitating conditions experienced by heart failure patients was thought to be due to a reduction in the amount of blood and oxygen supplied to the muscles by the heart.
An experimental drug, which plugs the leak of calcium and thus increases exercise capacity and reduces fatigue, was tried on mice.
Without the drug, the mice were found to be exhausted after three weeks of daily 3-hour swims. With the drug, the mice were still energetic, had lost less exercise capacity after 3 weeks, and their muscles showed fewer signs of calcium leakage, atrophy, and less muscle damage.
The drug is not yet available to people. Even if current researches on the drug prove to be successful, it will take several years before the drug becomes commercially available.