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Ton Van Den Bogert
02-13-2008, 06:54 AM
The following may be of interest to Biomch-L subscribers.

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Ton van den Bogert, Biomch-L co-moderator
http://www.Biomch-L.org

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Chang W. Lee/The New York Times
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.

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:
http://www.nytimes.com/2008/02/12/health/research/12musc.html

ScienceNOW news article:
http://sciencenow.sciencemag.org/cgi/content/full/2008/212/3?rss=1

PNAS publication:
http://www.pnas.org/cgi/content/full/105/6/2198

Muscle physiology and muscle mechanics:
http://muscle.ucsd.edu/musintro/jump.shtml