Exercisers and athletes can expect to feel fatigued when their blood sugar levels drop. Researchers at Loughborough University, UK showed that athletes who did not take sugar during soccer competition lasting 90 minutes felt more tired, had less competitive desire, and had far lower blood sugar levels than athletes who took a sugared drink every 15 minutes during their game.
Your brain gets more than 98 percent of its energy from sugar in the bloodstream. However there is only enough sugar in the bloodstream to last about three minutes. The liver must constantly release sugar into the bloodstream, but there is only enough sugar in the liver to last eight hours during rest and far less than that during exercise. So athletes who do not take a source of sugar during events lasting more than an hour can suffer the psychological effects of low blood sugar levels what include a mental feeling of fatigue and lowered competitive desire.
In another study, researchers at the University of Waterloo in Canada showed that taking sugar 30 minutes after starting to cycle and every 15 minutes afterwards increases strength, speed and endurance when exercising fairly intensely at 60 percent of maximal oxygen uptake. Muscles burn carbohydrates, fats, and protein for energy. Carbohydrates (sugars) require the least amount of oxygen for conversion to energy, which allows you to move faster with less effort. Athletes use sugared drinks, power bars or candy bars, concentrated sugared gels, cookies and almost any other source of carbohydrates during prolonged competition. It is possible to take in too much sugar and get a high rise in blood sugar if you are not exercising intensely, but this is rarely a concern for competing athletes. Competition takes great concentration, and eating and drinking are distractions that most athletes limit as much as possible. Journal references