When you eat a carbohydrate, your liver converts the food into glucose, a type of sugar whose main purpose and benefit when working out is to supply energy to your muscles and brain. Extra glucose is stored by the body as glycogen which is also used as fuel during exercise. Insufficient blood glucose levels during workouts can lead to fatigue, hypoglycemia and other problems.
Glucose: It's What's Fueling Your Workouts
Glucose, which is transported by your bloodstream to organs and tissues after eating carbohydrates, provides an essential source of energy for both your muscles and brain when working out. As energy and glucose needs to increase with exercise, it's important to eat enough carbohydrates in order to fuel your workouts. Having low blood glucose levels during exercise harms performance and can lead to physical and mental fatigue, sometimes resulting in weakness, dizziness and hypoglycemia. Glucose also prevents the body from using protein for energy. If working muscles have insufficient energy from glucose during exercise, they start using protein for fuel, which puts stress on the kidneys and diverts protein from its primary function of building and maintaining muscle.
Glycogen: Muscle Food for Atheletes
When glucose isn't needed for immediate energy, the body stores it as glycogen in the liver and skeletal muscle. Glycogen stores are especially important when working out, as the body's energy demands may exceed the amount supplied by glucose in the bloodstream after prolonged exercise or when exercising with insufficient carbohydrate intake. According to Iowa State University, during low-intensity workouts, glycogen stores can be used to increase glucose levels in the bloodstream for as long as 90 minutes -- whereas during high-intensity exercise, glycogen stores provide energy for only about 20 minutes. Active people therefore need to replenish glucose regularly by eating plenty of carbohydrates. However, in less-active people with adequate glycogen stores, additional glucose is stored as fat.
Getting the Most Glucose Benefit from Foods
To get the most glucose energy benefits for your workouts, complex carbohydrates such as starch and fiber are preferred over simple carbohydrates like the sugar found in juice or candy. Some common foods containing complex carbohydrates include whole grains, pasta and bread. Whereas eating a simple carbohydrate before working out can cause a sharp drop in blood glucose after about 30 minutes of exercise, complex carbohydrates which take longer to digest provide a slow, steady increase of blood glucose over several hours. According to Iowa State University, to ensure adequate glucose for a tough workout, you should consume a meal rich in complex carbohydrates two to four hours before working out and a carbohydrate snack one to two hours before working out. After working out for 90 minutes, drinking a sports drink can help replenish glucose.
Glucose and Exercising with Diabetes
Having adequate and stable glucose levels for exercise is especially important for people with diabetes whose blood glucose may fluctuate dangerously when working out. Therefore, people with diabetes and people taking medications that cause low blood sugar should monitor their blood glucose levels before, during and after exercise. Generally, 100 to 250 mg per deciliter, or mg/dL, is a safe pre-exercise blood sugar measurement, according to MayoClinic.com. If your measurement falls below this range you may be able to remedy it with a carbohydrate snack. If it is above 250 mg/dL, you may be at risk for developing a dangerous condition called ketoacidosis, and you should therefore postpone your workout until your levels drop to the safe pre-exercise range, according to MayoClinic.com.
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