The Olympic Torch Is Not The Only Thing That Was Burning in Athens

Aug. 23 - University of California Berkeley's very own Natalie Coughlin recently swam the 100-meter backstroke competition in Athens, she gave it her all and the games gave her the gold. She recently said that her body underwent a great deal of pain in that short period of time. "That last 50 hurt a lot, I got really excited that first 50 and I felt it the last 15 meters, definitely."   What is the reason for this painful last half of the race?

Scientists understand most causes of muscle fatigue.  New studies reflect that lactic acid, once diagnosed as an unwanted waste product and blamed for the burning feeling in fatigued muscles isn't what people thought.   Lactic acid helps muscles continue firing when they otherwise would cramp.    As well, and perhaps more importantly, we now know lactic acid is an important fuel source for working muscles, the heart and many other cells and tissues ranging from the brain to reproductive cells.

The misconception that lactic acid is a problematic waste product began almost a century ago when in 1907 Walter Morley Fletcher and Frederick Gowland Hopkins published one of the classic papers in the history of muscle physiology. Fletcher and Hopkins noted that when isolated, non-circulated and non-oxygenated frog muscle preparations were made to contract they accumulated a lot of lactic acid. Soon thereafter, in the 1920's one of the World's most famous physiologists Archibald Vivian (A.V.) Hill continued the work and concluded that lactic acid release in muscle was the signal for contraction, but too much lactic acid poisoned the muscles making them fatigue. The 1920's were amazing times in the history of muscle physiology with A.V. Hill sharing a Nobel Prize with the famous German biochemist Otto Meyerhof in 1924 and Hopkins the Nobel Prize in 1929 for the discovery of vitamins. Subsequently, Hill's idea about lactic acid sparking muscle contraction was shown to be wrong (calcium release triggers the use of ATP to power muscle contraction), but the World remembered the part about lactic acid and fatigue. Unfortunately, this was a scientific case of throwing out the baby with the bath water; the benefits of lactic acid production were forgotten. Now we realize the experiment was wrong. Hill studied the frog muscles in isolation with no circulating blood and no oxygen, so he couldn't know that within the muscles and body, lactic acid is utilized as a fuel.

"It was a classic mistake in biology," said Dr. George A. Brooks, a professor at the University of California at Berkeley and a pioneer in the evolving understanding of lactic acid metabolism and muscle fatigue. "But because those who did the work were Nobel laureates and because their students and disciples did not question the methods or conclusions of the frog muscle in a jar experiments, the mistake was propagated for years."

Even today, some coaches tell their athletes to concentrate on preventing lactic acid production and cleanse their muscles of lactic acid after a hard workout, with the idea that it is the culprit of second-day sore muscles.

Dr. Brooks has since proven that lactate from lactic acid is a fuel derived as the body breaks down carbohydrates. Skeletal muscles, the brain and cardiac muscle, a.k.a the heart consumes it eagerly, and is rapidly absorbed into the bloodstream to keep systems running. High levels of lactic acid can cause some sensation of muscle burn during exercise, but more of sensation is associated with release of phosphate and other ions in muscle. We know this because when people can't make lactic acid, muscle performance is poor and yet very painful. Now, new research shows that lactic acid serves as more than a fuel. In a study, appearing in the journal Science, Stephenson and others show lactic acid actually help keeps muscles contracting when they might otherwise become fatigued. To understand how, it's useful to look at what makes a muscle flex (contact) in the first place.

Thomas Fahey, an exercise physiologist at California State University in Chico, emphasizes that muscle actions are triggered by change in electrical charge across the muscle cell membrane, the normal electrical charge being maintained a mechanism known as the sodium-potassium pump. Continually, the sodium-potassium pump moves sodium ions out of a cell while pushing potassium ions in. Along with natural permeability differences, differences in levels of each kind of ion create the resting electrical charge. Muscle cells use this charge to respond to electrical signals coming from nerves and to contract. For every two potassium ions that are pulled in from outside the cell, three sodium ions are moved to outside the cell.

When a muscle is working hard, potassium ions can pass through the muscle cell membranes and build up outside the cell. This creates an ion difference that works to keep muscles from firing. Chloride ions also act as a braking agent. Trainers and coaches often know how to influence their athletes' physiology without really understanding the science behind it. They learn what works, through training, more training & trial and error. It can take a while for research based science to get relayed to coaches and explain why the body does what it does.

In this field Professor Fahey is no poser, he knows what it takes to be a great athlete as well as a coach. Dr. Fahey is a champion discus thrower, as well as a physiologist, explains that "Swimming coaches commonly measure lactic acid levels of their athletes to determine how fit they are."

Fahey explains, "This is an inaccurate test because a world class athlete could have both low or high levels of the acid, depending on the athletes last meal, as well as, how fast their bodies are using lactic acid and a huge array of other factors." Dr. Fahey believes that it doesn't really tell you much, in the end.

Whether or not such tests are truly instructive, they may offer something else - confidence. As all athletes know, what goes on in the mind during competition is often what counts most. So, if it helps build confidence to take a lactic acid test or a sugar pill - why not?

"Athletes try all kinds of crazy things. If Michael Phelps ate jelly beans, you'd probably have a bunch of swimmers suddenly eating jelly beans," said Fahey. "That's how we do sports - we look at what works, whether it's grounded in science or not."

Recently Cytosport had the opportunity to ask Dr. George Brooks a few questions about the latest science based research in sport nutrition.

Cytosport- "So Dr. Brooks it would seem Dr. Hill started a story about lactic acid that was not too accurate, is that true? What is the easiest way to explain this 'Burning' sensation in exercising muscles to the gym athlete or weekend warrior?

DR. B- "We have to give credit where credit is due. Hill and others observed that some lactic acid is helpful, but when muscles fatigue lactic acid is high. The latter observation was the result of the muscle preparation used. There was no oxygen-containing blood to supply nutrients, just the lower half of a frog with no blood, heart or lungs. So, the muscle's normal metabolism was affected and ionic balance was upset. The results obtained were the only ones possible, but that's not what happens in us.

Cytosport-"Dr.Brooks, why is lactic acid made in the body and what happens to it?"

DR. B- "Glycogen, the stored carbohydrate in muscle is the main fuel supporting contraction. As well, the blood sugar glucose is used but to a lesser extent. When muscles work hard, lactic acid is the result of glycogen and glucose use. This happens all the time, even in resting muscle and has nothing to do directly with the absence of oxygen. This misconception can be traced to the half-frog in a jar experiments. Usually in us the production of lactic acid goes unnoticed because lactic acid is either used in the muscle fiber of production, or in adjacent fibers. As well, some of the lactic acid escapes the muscle and is transported around the body in the blood to tissues like the heart and liver that take up and use the lactic acid. Mostly, lactic acid is used as a fuel, but some of it is converted by the liver and kidneys to glucose that is also used by cells and tissues. We know these things because we have studied the exchanges of atoms and molecules using isotopes, both within the body and within working and resting tissues. As well, we have infused a lactic acid/lactate cocktail into the blood of exercising men and shown that the lactic acid is used in preference to blood sugar. And finally, we and others have discovered that to make these exchanges, muscles and other types of cells and tissues have lactate transport proteins to speed the exchanges.

Cytosport- "Is it true that by ingesting a sports drink with PolyLactate, like Cytomax, you can actually exercise longer with less perceived exertion?"

DR. B- "We now know that during exercise we need to maintain blood sugar and provide carbohydrate energy. We know that the intestine has sugar and lactate transport proteins to hasten absorption into the circulation. We know also that both sugar and lactate are important and that lactate is used faster and preferentially. So, it makes sense to give the body what muscles are using." Cytosport- "Dr. Brooks, is it true that PolyLactate, will make the blood less acidic and is a preferred fuel of Cardio muscle? DR. B- "Thank you for asking the question. This is so important because of the history of misunderstanding; there are two ways to answer. For the chemist we can simply say that PolyLactate is a buffer to lactic acid because it is the salt of the acid. In lay terms we can say that the level of acidity depends on the ratio of acid to base, so adding PolyLactate actually lessens the acidic effects of lactic and other acids in the blood. Secondly, because the lactate in PolyLactate is a preferred fuel in red muscle, heart and other tissues, when the lactate is used so also is an acid proton removed. Hence, PolyLactate not only lessens the effects of acidic effects of protons, but PolyLactate also lowers the levels of acid protons."

Cytosport- "CytoMax has been a product that athletes have been counting on for over 15 years, there is only one other sports drink in America that has been around longer. The science of today that this telling us lactic acid is not as bad as we once thought, is already telling us about the flaws in the idea of proteins in sports drinks. What do you see coming up over the next 4 years in Sport Nutrition prior to the Beijing 2008 Olympiad?"

DR.B - "These are exciting times in science, sports medicine and sports nutrition. The more we know, the better we can train, refuel, rehydrate and recover for the next training session or event. I look forward to the implementation of more effective training regimens and dietary practices to optimize performance of athletes. More importantly, I look forward to broadening of knowledge in exercise physiology and sports nutrition to the general public for the benefit of the many, not only elite athletes."