Hypotonic = sub 4% Carbohydrate
Isotonic = 4 – 8% Carbohydrate
Hypertonic 8%+ Carbohydrate
PowerAMP Rapid Hydration has 3.2% sugar (Carbohydrates), putting it in the category of Hypotonic. Any increase in sugar levels beyond 4% has a negative effect on hydration.
Isotonic and hypertonic drinks (4+% carbohydrate) actually slow gastric emptying, the body needs more time to absorb the carbohydrates, resulting in slower uptake of fluid.
Typical sweat loss in an athlete is 1.5 – 3.0 litres per hour. Compare this with the rate of gastric emptying of water alone which is only 0.8 – 1.3 litres per hour. Drinking water alone will only slow the rate of dehydration. PowerAMP Rapid Hydration optimises the rate of gastric emptying from the stomach to the intestine at a rate which can exceed sweat loss and further improve fluid balance with both facilitated diffusion (Co-Transporter) and passive osmosis.
Sugar (Carbohydrates) can improve the taste of drink, and thereby promote its sales, resulting in an incentive for many companies to make isotonic and hypertonic drinks.
These drinks are usually marketed as a source of fuel and energy but in reality you need to have burned through all of you glucose stores for this to be effective (this takes multiple hours of exercise). You can also take carbohydrates in the form of snacks or gels, rendering isotonic and hypertonic drinks redundant.