Some 30 years of research at the University of California, Berkeley, however, tells a different story: Lactic acid can be your friend.
Coaches and athletes don't realize it, says exercise physiologist George Brooks, UC Berkeley professor of integrative biology, but endurance training teaches the body to efficiently use lactic acid as a source of fuel on par with the carbohydrates stored in muscle tissue and the sugar in blood. Efficient use of lactic acid, or lactate, not only prevents lactate build-up, but ekes out more energy from the body's fuel.
In a paper in press for the American Journal of Physiology - Endocrinology and Metabolism, published online in January, Brooks and colleagues Takeshi Hashimoto and Rajaa Hussien in UC Berkeley's Exercise Physiology Laboratory add one of the last puzzle pieces to the lactate story and also link for the first time two metabolic cycles - oxygen-based aerobic metabolism and oxygen-free anaerobic metabolism - previously thought distinct.
"This is a fundamental change in how people think about metabolism," Brooks said. "This shows us how lactate is the link between oxidative and glycolytic, or anaerobic, metabolism."
He and his UC Berkeley colleagues found that muscle cells use carbohydrates anaerobically for energy, producing lactate as a byproduct, but then burn the lactate with oxygen to create far more energy. The first process, called the glycolytic pathway, dominates during normal exertion, and the lactate seeps out of the muscle cells into the blood to be used elsewhere. During intense exercise, however, the second ramps up to oxidatively remove the rapidly accumulating lactate and create more energy.
Training helps people get rid of the lactic acid before it can build to the point where
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Contact: Robert Sanders
rsanders@berkeley.edu
510-643-6998
University of California - Berkeley
20-Apr-2006