People who exercise may know what it feels like to ‘feel the burn’. And most runners will have experienced ‘a stitch’ whilst running. Usually poor old lactic acid gets the blame. I have even heard people blame lactic acid for their cramps.
But what is lactate and lactic acid and why does it why does it get such a hard time? This post aims to dispel some of the common myths regarding lactate. I make no apologies, it gets a bit geeky...
Myth 1. Lactate is acidic
Strictly speaking, an acid is a substance that is able to donate hydrogen ions (H+). Lactic acid is such a substance. When it donates a hydrogen ion the resultant product is referred to as the conjugate base of the acid and in this case is Lactate. The body does not store lactic acid but quickly breaks it down to lactate. Lactate itself is therefore not an acid!
Myth 2. Lactate is a waste product
Wrong. Lactate and lactic acid for some time have been considered a waste product resulting from a lack of available oxygen to the working muscles. Far from being a waste product, the formation of lactate allows the metabolism of carbohydrates to continue through glycolysis. The heart, brain and most slow twitch fibres are very good at clearing lactate from the blood and in some cases lactate may actually be the preferred source of fuel. The vast majority of lactate produced is reused and is not a waste product.
Myth 3. A Lactate build up causes our muscles to burn
Nope. The burn or ‘stitch’ you may feel is thought to be due to the acidity, or excess of H+ ions, of muscles during exercise. Lactate, as we now know is a conjugate base and therefore helps to mop up these excess hydrogen ions. Lactate actually prevents muscle acidosis by transporting H+ ions out of muscles.
Myth 4. Lactate hangs around the body for days and causes ongoing soreness.
During and after your workout, your muscles and heart can metabolise lactate for energy. Your liver clears lactate from the bloodstream by converting it into glucose. The liver can also convert lactate into amino acids, the building blocks of proteins. Some lactate is lost in your sweat as well. All of these processes contribute to the rapid clearance of lactate from your bloodstream after exercise. Nearly all of the lactate you produce during a workout is cleared within 30 to 60 minutes, even after very intense exercise. Performing an active cool-down after your workout will help clear lactate more quickly than simply resting.
Myth 5. Massage therapy can clear lactate
Lactate accumulation after vigorous anaerobic exercise is cleared rapidly and efficiently by the body. This occurs on the cellular level via metabolic pathways and not by soft tissue therapy. However, massage therapy may help the mechanical symptoms of delayed onset muscle soreness, or DOMS, which is muscle soreness that typically develops a day or two after exercise. DOMS results from microscopic damage to your muscles, usually from exercises that you are not accustomed to doing.
What is the lactate threshold?
Anaerobic power and capacity (creating energy without the use of oxygen) are essential elements in sports where brief and explosive movements are required. Take a 100 metre race. If you're running at full capacity your body will not be able to meet your energy demands through respiration and oxygen intake. Anaerobic pathways take over and lactate levels will eventually build in blood.
In contrast, if you pace yourself well throughout a marathon race, you may never need to rely on anaerobic power as your energy requirements may be met through breathing and aerobic glycolysis pathways. This is providing you do not cross your anaerobic threshold, the point at which body demands cannot be met by aerobic metabolism and anaerobic takes over. This threshold is also sometimes called lactate threshold as vigorous exercise beyond this will cause lactate blood levels to rise.
(NB. The above description is hugely simplified. In reality there is no real 'distinct threshold' as aerobic and anaerobic pathways are being utilised all the time, just in varying degrees, but you get the idea...)
The anaerobic or lactate threshold is often a marker of fitness and can be trained over a period of time. Primarily for three reasons;
1. Lactate utilisation increases
2. Lactate production declines and
3. Lactate clearance increases.
Lactate in sport
In elite athletes, lactate levels are tested throughout their year/season to determine their lactate threshold. This is done by a simple pin prick blood test after a predetermined vigorous exercise programme. This acts as a marker of their fitness levels. The longer it takes an athlete to reach their lactate threshold, the greater their aerobic capacity and cardiovascular reserve must be.
Knowing your lactate threshold can help you determine how hard to train or when to push yourself during a race
Why does any of this matter to me?
Amazingly, some heart rate wrist monitors can estimate your lactate threshold by using your heart rate responses to set running protocols, without a drop of blood in sight. For experienced runners, the threshold occurs at approximately 90% of their maximum heart rate and between 10k and half-marathon race pace. For average runners, the lactate threshold often occurs well below 90% of maximum heart rate.
Knowing your lactate threshold can help you determine how hard to train or when to push yourself during a race. If you know you are exceeding your lactate threshold 5km into a half-marathon race, then there is no way that pace will be sustainable. Whilst training however, you want to be pushing your lactate threshold on occasion to gain the maximum cardiovascular and health benefit!
By training smart you should see your lactate threshold rise over time. But more importantly, by having a basic understanding of the science behind how our bodies create energy, this gives us another tool to help us train better and maximise our results.
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