Lactic acid is well known as the evil substance that makes legs stop working on hard climbs, but its power can also be used for good
It can happen on steep hills; it can happen when sprinting or time-trialling. We’re talking about the burn – the pain in your legs letting you know that whatever it is you’re doing, your body doesn’t like it. The catchall phrase for this has come to be known as a ‘build up of lactic acid’ and it’s been blamed for more evil deeds in the peloton than Lance Armstrong. Everything from fatigue to cramp to delayed onset muscle soreness (the dreaded DOMS) has been laid at the door of lactic acid. Common knowledge dictates that it is a very bad thing indeed.
Except that it’s not. In fact lactic acid is very definitely a good thing that not only powers your rides but can also be used to improve performance.
The hard cells
Lactic acid, or lactate (they are not exactly the same thing, but for the purposes of this article the terms are interchangeable) is a chemical compound produced by the body as a result of the oxidisation of glucose, particularly but not exclusively during strenuous exercise. That’s the simple bit. Now it gets more scientific…
‘On a cellular level the energy your body runs on exists as a molecule called adenosine triphosphate [ATP],’ says Xavier Disley, exercise physiologist and elite coach for RST Sport. ‘We have about 100g of ATP in the body but that only lasts for a couple of seconds so we have three main energy systems whose job it is to create ATP so that we can replenish our stores. Two of these occur without the presence of oxygen [anaerobic], while the other occurs with oxygen [aerobic].’
The aerobic system is generally the one most cyclists are interested in because as long as you don’t overexert yourself – and you don’t stop breathing – your body can break down fats and carbohydrates all day long.
The anaerobic systems are used for much shorter periods: the alactic [without lactate] anaerobic system is the first one recruited when performing high-intensity exercise and lasts for 10 seconds or less. ‘When you exercise from those 10 seconds to up to a minute you’re using the lactic anaerobic system for fuel,’ says Disley. This basically means that performing high-intensity exercise for up to a minute uses an energy system that increases lactic acid production. In this situation your body can’t clear it fast enough so it builds up.
It’s not all bad
There is some good news, however. ‘Lactate is also a significant fuel as well as an indicator of fuel use,’ says Dr Hannah Moir, senior lecturer in health and exercise prescription, School of Life Sciences at the University of Kingston. ‘Your body produces it all the time [even when you’re not exercising it’s produced as part of the body’s metabolism] but there’s a limit to how much you can have in your system. The point at which there’s too much for your body to clear properly is known as your lactate threshold.’ There are different names for the lactate threshold – you may hear it referred to as the anaerobic threshold or onset of blood lactate accumulation (OBLA) – but they all mean the same thing.
Once you reach that threshold, lactate is removed from the body in two ways: via oxidisation back into the muscles or conversion to glucose in the liver. These processes actually go on to help rather than hinder performance once your body returns to an aerobic state – by restoring energy to the cells and replenishing glucose levels, hence the idea that it is a ‘fuel’. And there is another benefit: the production of lactate regenerates nicotinamide adenine dinucleotide (NAD+), an essential coenzyme in cells that’s used up during exercise.
‘Lactic acid is definitely not a poison,’ says Disley, ‘But if you’re going really, really hard at the end of a time-trial you will feel it. When there’s not enough oxygen around the body to metabolise it, your blood lactate goes through the roof and you start to die – metaphorically speaking.’
Pain and gain
‘In the past, people have associated muscle pain with lactic acid,’ says Disley. ‘This was because lactic acid is tracked through blood lactate and it was assumed that when it was high, it was causing pain. The problem is when you start talking about muscle acidosis [acidosis is increased acidity in the blood and body tissue as a result of lactic anaerobic exercise] and the muscle pain that happens during and after exercise. The body may react to the presence of an abundance of lactic acid but that hasn’t got anything to do with DOMS. The reason you get DOMS is due to muscle cell damage or the inflammatory response to that damage.’
‘Muscle pain emphasises the myth that lactic acid is bad for you,’ says Moir. ‘It was traditionally considered a waste by-product that resulted in the muscle damage and pain caused by overexertion. The perception has now shifted from lactate being a waste product to it being an essential molecule in the signalling process of fatigue, recovery and tissue repair, particularly muscle hypertrophy [the increase in volume of the muscles’ cells as a result of exercise].’
The traditional belief that the build-up of lactic acid causes tiredness and fatigue if you push too hard is only partly true. ‘Once the body is unable to cope with the increased production of lactate, the blood pH becomes acidic,’ says Moir. ‘This increased acidity under anaerobic conditions results in the development of fatigue but doesn’t actually make you tired per se.’
In fact it’s the chain of events in which the acidity of the blood increases that causes the inactivation of various enzymes involved in the energy transfer. This results in the impairment of your muscles’ ability to contract. In other words, it’s not the lactic acid itself that tires you out, it’s how your body reacts to it that can cause fatigue.
Find your level
Just because lactic acid isn’t actually harmful or fatiguing in itself, as was once believed, you don’t want to ride at a level where your body is producing so much that it has a negative effect on performance. The term lactate threshold suggests it’s something that can be increased, but that couldn’t be further from the truth.
‘Your own particular blood lactate is like a fingerprint, so it will vary from person to person,’ says Disley. ‘Just because you’re an Olympic athlete doesn’t mean you’ll have a higher threshold than the average Joe – in fact sometimes it’s the other way around.’
Your lactate threshold is a predictor of your performance but doesn’t govern performance itself – it’s simply the amount of power you can produce at your given threshold that counts.
‘The average lactate threshold is 4 millimoles per litre of blood [mmols/L],’ says Disley. ‘If the amount of lactate in the blood goes above that it will start to accumulate, which is when you get the downward spiral. We’d look at what performance can be achieved at that average level over, say, a one-hour time-trial and then work with the rider to improve their performance. At RST we use power meters. You can apply the same principles when using a heart rate monitor although it’s not as accurate.’
You may see this protocol referred to as lactate tolerance training, which brings to mind images of riders chewing their handlebar tape to physically resist the effects of the lactate build-up. Again it would appear to be another instance of the terminology dictating the meaning. ‘It’s not about tolerating extra lactate in the body,’ says Disley, ‘It’s about being able to eke out the particular power output at that level. You’re not tolerating the lactate better, you’re just getting better at that level. It’s got nothing to do with being more hardcore mentally or physically – it’s about your physiology improving which allows you to perform at a higher workload threshold.’
All this information is academic if you don’t know what your lactate threshold is. Getting it tested in a lab can be expensive, but it’s worth contacting your local university’s exercise science lab and putting yourself forward for one of their study groups. You’ll be able to get your tests done as part of their research work, and that data will be free.
However, if that isn’t an option and you have a heart rate monitor you can find what your heart rate is at your lactate threshold with this DIY time-trial. Plan a three-mile route that you can ride without stopping and set your HRM to tell you your average heart rate. Warm up for 20 minutes, then ride the route as fast as you can. Ride back to the start of your route at an easy pace, then repeat the test. Your heart rate at your lactate threshold is approximately the average heart rate of the two tests. You can use this figure for threshold training, for example by performing intervals while staying just below that heart rate.
Short and sweet
It’s taken time to reach the conclusion that lactate isn’t an enemy, but it’s not been for the want of trying. ‘It’s not down to a lack of research because people have spent a lot of time looking at it,’ says Disley. ‘The simple fact is it’s really hard to study the different ions, chemicals bases, acids and alkalines that occur at such a cellular level.’ In fact, such is the shift in perceptions we may not be that far off supplementing with lactic acid. ‘In the lab you can improve someone’s performance by giving them lactic acid in the form of calcium lactate,’ says Disley. However, don’t bother heading down to Boots just yet to stock up before your next gran fondo: ‘You only see its benefit in the very, very short and intense stuff – so unless you’re a 500m time-triallist or track rider you probably won’t notice the difference
Lactic myth busters
Four widely held beliefs about lactic acid that just aren’t true
- Lactate exacerbates muscle damage and causes pain
Not so. ‘Lactate is essential in the development of adaptation to exercise and is key in stimulating the production of growth hormone, which in turn is involved in muscle growth and strength gains,’ says Dr Hannah Moir. - You want to reduce the amount of lactate you produce
Nope, you want more. ‘Inducing lactate is key in the development of strength and power,’ says Moir. ‘Training to improve your ability at the lactate threshold in aerobic exercise enables individuals to perform harder and for longer.’ Which is the Holy Grail of pros and sportive riders alike. - Lactic acid hangs around in the body for days causing pain If someone boasts about how they can feel the lactic acid in their muscles the day after riding, feel free to tell them they’re wrong. ‘Your lactate level stays high for 4-6 minutes then goes down over the next hour,’ says exercise physiologist Xavier Disley. Active recovery, which promotes blood oxygenation, reduces it even more quickly.
- Lactate is produced only when you exercise hard
‘It’s not a substance that’s suddenly produced when you exercise,’ says Disley. ‘It’s in your body the whole time. It’s only when you exercise past a particular point and you can’t get rid of the excess lactate where you start to slow down and can’t carry on.’
