Buffers – Reducing blood acidity benefits performance

Fatigue in the body can occur for various reasons. In a previous post I described a theory of fatigue where the brain unconsciously regulates your pace, to prevent anything harmful from occurring. I’ve discussed hypoglycaemia or “hitting the wall” as one of those harmful events, when the body's supply of carbohydrate is used up. In this post we’ll look at blood acidity during high intensity exercise, and the nutritional supplements that offer the potential to boost performance.

Blood acid/alkaline balance – tightly controlled

The acid alkaline balance in your blood (blood pH) is kept within a very tight range, using a range of mechanisms to control it. If it ventures too far outside these limits, the result can be catastrophic. Increased blood acidity (reduced pH) is known as metabolic acidosis. It can occur for a variety of reasons including certain medical conditions, and if untreated can be fatal. Of course your brain is far too smart to let that happen during exercise, and I’ve never heard of anyone developing metabolic acidosis during sport.

High intensity exercise causes a rise in blood acidity (reduced pH)

During high intensity exercise the body is demanding large amounts of energy to be generated very quickly. As the intensity increases we need to use more fuel and more oxygen to create the energy, just like a car. However there comes a point when the amount of oxygen required exceeds what the body can deliver. The body can produce energy without adequate oxygen (anaerobic exercise), however as a by-product the muscles produce lactate and hydrogen ions. Sporting events that involve anaerobic energy production are typically high intensity events lasting 40 seconds to 6 minutes such as rowing, most swimming events, 400, 800 and 1500m running, and some track cycling events. There’s also longer races where short bursts of anaerobic exercise can make the difference between winning and losing, such as mountain biking, adventure racing and road cycling.

Despite popular belief it’s not the lactate that’s the problem in anaerobic exercise, but the hydrogen ions. If you ever did high school chemistry you’ll probably remember that hydrogen ions cause a fall in pH (ie. rise in acidity). This pH drop initially occurs in the muscle, but as hydrogen ions are released into the bloodstream the blood pH can start to fall as well.

Reduced blood pH causes fatigue

Because our blood pH must be kept within a very strict range to keep us healthy, it’s no surprise that the brain works hard to prevent us from producing too many hydrogen ions. This is where fatigue enters the picture. Our brain works to prevent the pH of the blood falling too low before we finish an exercise session. It does this by activating less muscle fibres in a contracting muscle group during exercise, to slow you down and prevent pH from reaching dangerous levels. At the same time you’ll be consciously aware of the physical and psychological stress that develops during high intensity exercise. This is your Rating of Perceived Exertion (RPE - how hard you feel you’re working) increasing. Eventually your RPE will get to a level where it is simply too unpleasant to continue exercising at that pace, and no matter how strong willed you are you can’t push yourself through it.

Buffers – preventing the fall in pH

This is where buffers become important. A buffer is any substance that reacts with hydrogen ions to neutralise their acidity. Not surprisingly the human body contains several buffers which can help to neutralise at least some of the hydrogen ions produced during anaerobic exercise. In the bloodstream bicarbonate is the main buffer, whilst in the muscles carnosine and phosphate act as buffers. Buffers allow us to produce more energy anaerobically whilst slowing the decline in blood pH. Since it’s the pH that the brain is concerned about, buffers allow you to produce greater high intensity bursts during sport. The difference is subtle, but can be enough to make the difference between winning or not in competition. We know that athletes that excel at events where anaerobic energy production is crucial have a higher buffering capacity than other people.

Nutritional supplements to increase the body’s buffering capacity

Nutritional supplements are used to boost the body’s ability to buffer the hydrogen ions. The first supplement to be used as a buffer was sodium bicarbonate. It increases the bicarbonate in the blood, which reacts with the hydrogen ions to prevent a change in pH. Ural, a dissolvable powder used to treat urinary tract infections, is commonly used as a source of sodium bicarbonate. Early experimentation with bicarbonate supplements were not particularly successful, because when bicarbonate mixes with water it creates carbon dioxide, and athletes experienced extreme stomach and bowel discomfort, bloating and in some cases severe diarrhoea. However in recent times sports scientists and dietitians have refined the protocols for using sodium bicarbonate which minimise the side effects whilst delivering the performance benefits.

The other nutritional supplement that has been used as a buffer is beta-alanine. Beta –alanine is one half of the carnosine molecule, which in the muscle acts as a buffer before the hydrogen ions are even released into the blood. The body has plenty of the carnosine’s other half L-histidine, so providing extra beta-alanine from supplements allows the body to produce much more carnosine in the muscle. Beta-alanine isn’t without its side effects either – a single large dose can cause blood levels to rise to a point that causes flushing and pins and needles. However taking the supplement in several smaller doses, or in slow-release capsules helps to minimise these symptoms.

Summary

During very high intensity exercise the body requires more oxygen to produce energy than what it can bring in. The body can still produce energy without oxygen, but as a result it produces lactate and hydrogen ions. The hydrogen ions cause a rise in acidity (fall in pH), firstly in the muscle but then in the blood. The blood pH is controlled within a very tight range, and the brain will work very hard to prevent the pH falling too low. It achieves this by activating less muscle fibres during exercise, and by increasing your Rating of Perceived Exertion – your feeling of fatigue.

Our body naturally contains substances that react with the hydrogen ions, helping to “buffer” or delay the fall in pH. Buffers exist both in the muscle and in the bloodstream. Two nutritional supplements can be used to increase the body’s own buffering capacity. This  allows you to exercise for slightly longer or at higher intensities. Sodium bicarbonate supplementation increases the bicarbonate level in the blood, whilst beta-alanine supplementation increases the body’s muscle carnosine levels. Both will work as buffers, and can potentially enhance performance in sports that involve very high intensity efforts of longer than 40 seconds.

In the next post we’ll start to look more closely at these buffering supplements. We’ll look at how they work, what sports they will be beneficial for, and how to take them.