Lactic Acid

It’s not uncommon to view lactic acid as an enemy. For decades we’ve been conditioned by teachers and 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. 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.

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. Thomas Fahey, PhD, professor of Exercise Science at California State University, 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 it’s used as a building block to make liver glycogen. This is called the "Glucose Paradox" and should remind us why it’s so important to have a healthy liver and active muscles. Under anaerobic conditions, lactate even becomes a primary fuel for the brain.

Lactic acid is enormously important in how we adapt to stress. When it’s correctly managed it is possibly one of the most important keys to athletic success in high intensity sport. Research with rats 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 (hGH) from the pituitary. That’s good because both of these hormones generally take a nosedive as people age. It’s not known yet whether it’s the lactate ion or the intense anaerobic exercise that causes hGH to be released, but there is definitely a correlation.

The Real Pain in the Butt

Lactic acid does not cause that dreaded burning sensation during intense exercise. Lactic acid is formed from the breakdown of glucose, our body’s main source of carbohydrate. When made, it’s split into a lactate ion (lactate) and a hydrogen ion. The hydrogen ion is the bad guy–the acid in lactic acid that interferes with electrical signals in nerve and muscle tissue. When the rate of lactic acid entry into the blood exceeds our ability to control it effectively, then those pesky hydrogen ions begin to lower the pH of muscle. This invariably interferes with how the muscles contract and thus our ability to perform.

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 and in Optimum Sports Nutrition, Dr Michael Colgan clearly describes how causes of both muscle damage and DOMS include ammonia accumulation from muscle into the blood, compression hemolysis, reduction of cytochrome C and uncontrolled free radicals.

Athletes should take supplemental antioxidants before and after training, such as vitamin C and E, coenzyme Q₁₀, n-acetyl-cysteine (NAC), L-glutathione, grape seed extract, beta carotene, niacin, B₅, zinc and selenium.

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, particularly to endurance muscle fibres. This is one of the reasons why I teach my clients to perform cardio after the resistance exercise segment of their workout, not before. We also oxidize fatty acids more efficiently after glycogen has been depleted.

Lactic Acid Metabolism

Some supplements can help protect against the negative effects of lactic acid metabolism. The first that comes to mind is creatine. In Creatine, The Power Supplement, Richard Kreider, PhD explains that increasing phosphocreatine through creatine supplementation may enhance performance by buffering acid [hydrogen].

The supplement known as fl-hydroxy-¾-methylbutyrate (HMB) 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. This supplement seems to help the body burn intramuscular fatty acids preferentially over carbohydrates. It also increases the lactic acid threshold.

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 per cent) at least 60 percent of your dietary profile should consist of alkaline food. But that’s another whole article in itself!