It seems like every second advert on the TV now is for a sports drink. Sports stars are featured using them, from Brian O’Driscoll to Sean Ó Hailpín and Damien Duff. These drinks make a lot of claims about improving performance and endurance, so how do they work?
To understand this, we need to look at how exercise affects your body chemistry.
Exercising involves a complex chain of chemical changes. (Image: London School of Economics)
Whether you’re running, walking, swimming, or playing football, your muscles are working more than they normally would. To work efficiently, your body chemistry changes.
Working muscles need lots of oxygen. This is delivered to your muscles and organs by blood, so exercise puts increased demands on your heart and lungs. Your heart beats faster to supply the blood and your lungs gulp in the air to get the oxygen from it.
Here’s the technical bit. The chemical equation for respiration and aerobic exercise is:
C6H12O6 + 6O2 = ATP + 6H2O + 6CO2
Or (more simply): glucose + oxygen = ATP + water + carbon dioxide.
ATP in that equation stands for adenosine triphosphate (C10H16N5O13P3).
ATP is an energy carrier, a bit like a truck transporting energy from one part to another, so it’s needed to think, breathe or contract muscles, and it’s recharged with food.
For this to work, your body needs three things to happen:
- As with any form of combustion, your body needs oxygen to burn or use ATP (so you inhale a lot).
- Your body needs to stay cool and get rid of excess heat (you sweat).
- Your body also needs to get rid of waste produced in this process (you exhale and your body breaks down lactic acid into its constituent parts to dump or reuse).
If you can’t get the oxygen to your cells fast enough, your system uses whatever else is available to create ATP: it uses lactic acid. The chemical equation for anaerobic exercise goes like this:
C6H12O6 = 2 C3H6O3 + 2ATP
Or, in simpler terms: glucose = lactic acid + energy.
The presence of this acid is the reason why your muscles feel sore while exercising (although, contrary to popular belief, it’s not why they feel sore after exercising).
If Your Body Doesn’t Get Enough Water
If you don’t have enough water in your system while exercising, your body temperature rises and there’s an even greater need to bring water to the sweat glands.
Blood is about 50% water, which is why blood that is being used to transport oxygen and nutrients to your muscles has to be diverted to do this, so your muscles don’t get what they need. This leads to a poorer performance.
Sweating also involves the loss of essential salts or electrolytes such as sodium, potassium and calcium ions. These are central to healthy cell communication and affect how your muscles contract, so replacing them is crucial.
Your body needs a lot of water to maintain performance. (Image: Mark Hillary)
So where do sports drinks come into all this? Isotonic drinks contain electrolytes and carbohydrates. When you’re engaged in strenuous activity, secondary bodily functions like digestion often ‘shut down’.
Isotonic drinks with small amounts of glucose are an alternative to eating solids – they are a quick and light way to give your body the food it needs to keep going. If you can manage a sip or two every 20 minutes during exercise it can prevent an energy crash.
The drinks are fortified with essential salts too, so drinking them can help to maintain cell function and prevent dehydration. Flavours are also added, but this is just to make the drinks tastier.
Make Your Own
The bottom line is that isotonic drinks really do work and it’s simple to make your own. Here’s a basic recipe for one litre:
- 200ml of fruit squash/concentrate
- 800ml of water
- A pinch of salt
Mix and enjoy.