Sports drinks are generally categorized into three distinct varieties: Isotonic, Hypertonic and Hypotonic. Brands such as Lucozade and Powerade use these words as marketing instruments, but what do they really mean? Tonicity refers to the concentration of the solution as compared to that of the human body. Iso means equal to, hyper means greater than and hypo less than. This is important, as it tells us how much carbohydrate/energy can be delivered or absorbed into the body, in order to replace fluids you have lost.
These drinks contain different amounts of carbohydrates (principally sugars) and electrolytes (salts). The drinks are beneficial for different types of exercise. They can enhance performance, endurance and recovery when consumed before, during or after exercise.
The carbohydrate in the drinks helps replace the body’s energy stores, muscle glycogen, the primary fuel source during exercise. Sodium is the main electrolyte lost when you sweat. When too much sodium is lost through sweating, the body’s electrolytes become unbalanced and it is important to replace them.
Hypotonic drinks contain the least carbohydrate and sodium out of the three. They are effective at transporting water back into your cells, as the concentration of electrolytes is less than that in your body. The water from the drinks moves via osmosis into your cells, hydrating you. Hypotonic drinks (such as Lucozade’s’ zero calories) have been found to be most effective when hydrating before exercise or during light-moderate exercise that lasts up to an hour.
Isotonic drinks are of similar concentration to human blood (285- 295 Osm/kg). They tend to be composed of around 6-8% carbohydrate and contain electrolytes. Also, they are the most common type of sports drink found on supermarket shelves. Isotonic drinks tackle the two biggest causes of fatigue during exercise: dehydration and lack of energy. Studies have shown that they prove most effective during moderate-intense exercise lasting longer than 60 minutes or for intense bursts of exercise lasting no longer than 30minutes.
The nutritional information of sports drinks from iconic brands. The photos below show a hypotonic, hypertonic and isotonic drink, in that order.
Hypertonic drinks contain the greatest concentration of carbohydrates. They very rarely contain electrolytes, examples include Lucozade’s ‘energy’ range. They are often referred to as energy drinks, as they aim to replenish energy used by the body and should be used post exercise. The main purpose of these drinks is not hydration, but recuperation after strenuous activity. The high concentration of carbohydrates results in a slower absorption rate of the fluid. Athletes that burn large amounts of energy for a sustained period, such as ultramarathon runners, often utilize hypertonic drinks.
Next time you reach for a sport’s drink, do your body a favor – choose wisely!
Written by Charlie Farmer
Want to read more about health and fitness nutrition. Read further on our blog and discover our “Monday Myth: Are Carbs the Enemy?”