Lactic Acid: Friend or Foe?
|Its not uncommon to think of lactic acid as an enemy. For decades weve been conditioned by teachers, coaches and personal experience to think of it as some kind of useless waste product; the cause of that burning sensation when you run fast or pump iron to complete failure. Of course almost everyone associates lactic acid with next-day muscle soreness, fatigue and stiffness. However, thanks to ongoing research in the field of nutritional biochemistry and exercise physiology, an entirely new perspective of lactic acid is now held. Instead of some kind of evil Darth Vader, scientists now recognize lactic acid as a major player in the way our bodies generate energy during exercise. Lactic acid is actually our friend. The Benefits of Lactic Acid
Lactic acid fuels glucose and glycogen production in the liver, helps us to use dietary carbohydrates more efficiently and actually serves as a quick energy fuel preferred by the heart and muscles. Under anaerobic conditions, lactate even becomes a primary fuel for the brain. Lactic acid is enormously important to mechanisms involved with how we adapt to stress, and when correctly managed is possibly one of the most important keys to athletic success in high intensity sport. Research with rats while swimming at high intensity has shown that lactate has a stimulatory effect on testosterone release. Lactic acid may also signal the release of human growth hormone from the pituitary. Thats good because both of theses hormones generally take a nosedive as people age. Its not known yet whether its the lactate ion itself or the intense anaerobic exercise (which increases lactate ion concentration) that causes hGH to be released, but there is definitely a correlation. The Real Cause of DOMS
Lactic acid does not cause that dreaded burning sensation during intense exercise. When lactic acid is made its split into lactate ion (lactate) and hydrogen ion. Hydrogen ion is the bad guy, the acid in lactic acid that interferes with electrical signals in nerve and muscle tissue. And lactic acid is not responsible for any muscle soreness felt the next day or two after a hard workout. That is caused by muscle damage and post-exercise tissue inflammation. Dr Fred Hatfield, author of Hardcore Bodybuilding: A Scientific Approach, associates delayed onset muscle soreness (DOMS) with hydroxyproline damage, caused by the production of superoxide free radicals, hydroperoxides, hydroxyl radicals and ammonia. Hydroxyproline is a constituent of collagen and occurs throughout connective tissue. In Optimum Sports Nutrition, Dr. Michael Colgan clearly describes how both muscle damage and DOMS are caused by the accumulation of ammonia, phosphate leakage from muscle into the blood, compression hemolysis (destruction of red blood cells), reduction of cytochrome C and uncontrolled free radical pathology. To offset this damage, which is potentially greater in large muscles such as the legs or back and rises with increased intensity, or in aerobic activity which forces a greater consumption of oxygen, athletes should take supplemental antioxidants before & after training, such as vitamin C & E, coenzyme Q10, n-acetyl-cysteine (NAC), L-glutathione, grape seed extract, beta carotene, niacin, B5, zinc and selenium. The Lactate Shuttle
Dr. George Brooks, PhD, professor of integrative biology at the University of California, Berkeley, claims that lactate can be shuttled between cells to supply additional energy for continued work. Lactate produced in fast-twitch (white) Type II explosive muscle fibers can be transported to slow-twitch (red) Type I endurance muscle fibers and throughout the entire vascular system to be used as fuel. This is one of the reasons why I teach my clients to perform cardio AFTER the resistance exercise segment of their workout, not before. The other reasons relate to the way we oxidize fatty acids more efficiently after glycogen has been depleted and as a preparatory step for the next and final segment of my Five Step Exercise Program©, which includes a full body stretch inclusive to the combined techniques of yoga, martial arts and dance. More on Lactic Acid
Lactic acid is formed from the breakdown of glucose, our bodys main source of carbohydrate. Although this process is oxygen independent, lactic acid is also formed and maintained in muscles that have plenty of oxygen available. The key issue is elevation above threshold, because when the rate of lactic acid entry into the blood exceeds our ability to remove and/or control it effectively, then those pesky hydrogen ions begin to lower the pH of muscle, which invariably interferes with how they contract and thus our ability to perform. Thomas Fahey, PhD, professor of Exercise Science at Cal State, Chico, says the body uses lactic acid as a biochemical middleman for metabolizing carbohydrates. Most glucose from dietary carbohydrate bypasses the liver and enters the general circulation where it reaches muscle and converts into lactic acid. Lactic acid then goes back into the blood and returns to the liver where its used as a building block to make liver glycogen. This is called the Glucose Paradox and should remind us why its so important to have a healthy liver and active muscles. Nutrients Which Improve Lactic Acid Metabolism
The first one that comes to mind is creatine. In Creatine, The Power Supplement, Richard Kreider, PhD explains that increasing phosphocreatine [in the myocyte] through creatine supplementation may enhance performance by buffering acid [hydrogen ions], mitigating the formation of lactic acid and reducing the reliance on anaerobic glycolysis as a replenishment source of ATP. HMB (ß-hydroxy-ß-methylbutyrate) is also a great asset. Steven Nissen PhD has shown that athletes taking HMB can exercise at a higher intensity and/or for a longer period of time when compared to a placebo. HMB seems to help the body burn intramuscular fatty acids preferentially over carbs. HMB improves VO2 peak, increases the time it takes to reach VO2 peak and increases lactic acid threshold. For more info and references, check out www.mettechinc.com. Hydration is monumental to health & performance and its surprising how few people including athletes adequately hydrate themselves. A group of scientists in the United Kingdom examined the effects of ingesting a 6% carbohydrate-electrolyte solution on athletes (versus a placebo) during 90 minutes of intermittent high-intensity running. Serum insulin and blood glucose concentration was maintained for longer periods and blood lactate after 30 minutes of exercise was lower compared to water only (Medicine & Science in Sports & Exercise, September 1999). Sodium bicarbonate and phosphate both help beat the burn. So do carnosine and carnitine. Standardized panax ginseng extract spares glycogen and increases fatty acid oxidation. When you spare glycogen as a fuel source in exercise you can usually extend the time it takes to reach your tolerance to acid as it builds up. Of course the food you eat also contributes in a powerful way. Unlike the Canadian average (20%) at least sixty percent of your dietary profile should consist of alkaline food. But thats another whole article in itself! References
Fahey, T., PhD, Dont Dis Lactic Acid, Sports Science, Volume 36, Number 9, Muscular Development (September 1999) Boettger, C., MS, The Lactate Shuttle, Sports Research Update, Muscle & Fitness (February 2000) Brooks, G.A., Mammalian fuel utilization during sustained exercise. Comparative Biochemistry and Physiology. Biochemistry and Molecular Biology 120 (1): 89-107 (1998) Gladden, L., Lactate uptake by skeletal muscle. Exercise Sport Science Review 17:115-155 (1989)