Finding May Solve Riddle of Fatigue in Muscle

By GINA KOLATA
Published: February 12, 2008

One of the great unanswered questions in physiology is why muscles get tired. The experience is universal, common to creatures that have muscles, but the answer has been elusive until now.

A New Explanation of Muscle Fatigue

Scientists at Columbia say they have not only come up with an answer, but have also devised, for mice, an experimental drug that can revive the animals and let them keep running long after they would normally flop down in exhaustion.

For decades, muscle fatigue had been largely ignored or misunderstood. Leading physiology textbooks did not even try to offer a mechanism, said Dr. Andrew Marks, principal investigator of the new study. A popular theory, that muscles become tired because they release lactic acid, was discredited not long ago.

In a report published Monday in an early online edition of Proceedings of the National Academy of Sciences, Dr. Marks says the problem is calcium flow inside muscle cells. Ordinarily, ebbs and flows of calcium in cells control muscle contractions. But when muscles grow tired, the investigators report, tiny channels in them start leaking calcium, and that weakens contractions. At the same time, the leaked calcium stimulates an enzyme that eats into muscle fibers, contributing to the muscle exhaustion.

More at the NY Times

The athletes at the Fire Department take this special medicine called HTFU. Works wonders for this "fatigue" problem.