It is amazing what an enormous role the media plays in our lives and in our perception of certain things.
For years butter got a really bad rap for being unhealthy, and margarine was the way to go. Then there was "a study" that found the opposite to be true, so everyone was back on butter.
Well the same scenario seems to be playing out in many recent forums and publications about Lactic Acid.
There has been a resurgence in discussions on and around Lactic Acid: Is it good? Is it bad? Can it be used to make more energy? Is it a waste product? Does it cause the burning felt in the muscle during intense activity? Does it cause muscles soreness? Is Lactate Threshold Testing dead?
There have been some pretty interesting postulations and ideas tossed around, a few with validity, others, not so much.
As a Sport Scientist, Bioenergetics (the means by which the demand for energy is met in the body) has always been one of my favorite areas of study, and as an Endurance athlete and Triathlon Coach, it has helped me better understand just how it fits into the programming and training continuum.
So let's break break things down: (Please put on your brainiac hats)
- There are 2 by-products of Glycolysis: Pyruvic Acid and Lactic acid.
- Lactic Acid is a by-product of Anaerobic energy production (Anaerobic Glycolysis)
- Anaerobic Glycolysis utilizes primarily Carbohydrate energy sources to produce energy.
- Lactic Acid does not build up at all Training Intensities, but begins to accumulate when the bodies demand for energy starts to exceed its ability to produce it, via Aerobic pathways. This leads to Anaerobic pathways being called on for more rapid energy provision.
- Lactic Acid is, in fact, a by product of the increased production of Hydrogen ions. This occurs when the production of Hydrogen exceeds the bodies ability to Oxidize them down the respiratory chain (Pyruvate accepts an additional Hydrogen Ion, and Lactic Acid is formed).
- Bottom line: Increased Hydrogen Ions are at the heart of the problem.
- Fast Twitch Muscle Fibers (FTF) are more prone to create Lactic Acid than are Slow Twitch Fibers (STF). An enzyme found in both Fibers (LDH), in FTF favours Pyruvic Acid conversion to Lactic Acid, and in STF, favours the conversion of Lactic Acid to Pyruvic Acid.
- Lactate Acid that is formed in one part of a muscle can be oxidized by another part of that muscle, or by less active tissue around the muscle where the Lactic Acid is produced (called the Lactate Shuttle.
- Lactic Acid, is no longer considered a metabolic waster product, but as a source of energy.
- It has been shown that Lactate can be used as a substrate for the liver to synthesize glucose from (Gluconeogenesis) i.e. a source of energy from which the liver can extract energy.
- Lactate can also be used as a direct energy source for skeletal muscles and the Heart.
- Lactic Acid does not cause the stiffness felt a day or 2 after intense phyical activity. What you are feeling is called D.O.M.S (Delayed Onset Muscle Soreness), and is a result of an increased amount Eccentric Loading (Placing a load on a muscle while it is stretched). For example after doing a Track, Interval Session.
- The burning you feel in your muscles during intense bouts of activity are also often blamed on Lactic Acid, and again, the culprit is actually the Hydrogen ion. This pain is caused by an accumulation of hydrogen ions that stimulate pain nerves located in the muscle. Performance decline is induced by both metabolic and muscular fatigue.
- There is, and has always has been, a question of whether Lactate Threshold (LT) is relevant or not. Well, in a number of research studies, it has been shown that LT can be used as a good predictor of endurance performance potential (along with many other parameters such as movement Economy).
- Is there any way to extend the time before performance becomes affected by Lactic Acid? Well a number of studies have been done on the impact of Sodium Bicarbonate loading on performance, and they showed that there was an increase in time to exhaustion and output levels of the athletes. This does not mean you should go out and start eating Baking Soda before racing - overdosing can cause extreme GI distress, cramping and pain.
The take away for us (Athletes and Coaches), is that nothing, no theory or research finding, can replace consistent and well structured training.
