Energy Use During Exercise
- Carbohydrates and fats are the primary sources of fuel during exercise, with carbohydrates being the predominate source.
- Be picky when choosing carbohydrate sources. Whole wheat breads, waffles, bagels and pasta, rice, potatoes with the skin intact, sweet potatoes, fruits, vegetables and dairy products are nutrient dense sources of carbohydrates. Sports nutrition products are formulated to provide the most absorbable forms of carbohydrates and are excellent choices for before, during and following endurance events.
- Consuming adequate carbohydrate on a daily basis is necessary to replenish muscle and liver glycogen between daily training sessions and/or competitive events.
- Carbohydrate loading can increase muscle glycogen (stored energy) by as much as 75%. You can “top off the tank” of muscle liver glycogen before an event by consuming carbohydrate-rich meals.
- Consuming carbohydrates before and during prolonged exercise (longer than 45 minutes) provides the body with a constant supply of glucose for sustained muscle performance and that all important mental edge.
- Inadequate carbohydrate intake is problematic, especially for those athletes whose performance depends on sustaining high-intensity exercise for prolonged periods.
Recommended Daily Carbohydrate Intake:
- 5-10g carbohydrate/kg
- 5-7g carbohydrate/kg for general training needs
- 7-10g carbohydrate/kg for endurance athletes
- Ultraendurance athletes have exceptional needs and often need more than 11g carbohydrate/kg
Carbohydrate Intake Prior to Exercise:
- The ideal pre-exercise meal or snack is carbohydrate-rich, palatable, and well-tolerated. A meal composed of complex carbohydrates, lean protein, and little fat is best. For endurance events lasting longer that 1-2 hours aim for 75% of your pre-event meal to be from complex carbohydrates.
- Experiment with low-, medium-, and high glycemic index foods during training. Many sports nutrition products are formulated with a blend of all three types of carbohydrates. Research shows that the combination of the three may provide the best results.
- Athletes should consider both the timing and the amount of carbohydrate prior to exercise. General recommendations are as follows:
Carbohydrate, g/kg Timing Prior to Exercise, hours
(Example: a 130 lb. (63kg) woman would need 63g (252 calories) 1 hour prior to exercise or 253g (1012 calories) 4 hours prior to exercise.
Carbohydrate replenishment during exercise:
- It is important to note that the goal is not to replace all of the used glycogen stores, but rather to deliver a constant supply of glucose to the muscles and brain.
- Carbohydrate intake during exercise is encouraged for exercise lasting longer than 45 minutes 1 hour.
- The ideal carbohydrate replenishment source is palatable and well-tolerated. This point cannot be emphasized enough. There are many effective sports nutrition products on the market. Taste and texture absolutely make a difference. If it doesn’t taste good going down, it is not going to sit well once its there.
Recommended Carbohydrate Intake During Exercise:
- Carbohydrate intake during exercise improves endurance performance as well as performance in stop-and-go sports.
- General recommendation is 30-60g carbohydrate every hour as food and/or fluid.
- Most athletes choose medium- to high-glycemic index foods.
High GI = glucose, bread, potatoes, breakfast cereal, sports drinks
Moderate GI = sucrose, soft drinks, oats, tropical fruits such as bananas and mangos
Low GI = fructose, milk, yogurt, lentils, pasta, nuts, cold climate fruits such as apples and oranges
- Research has indicated that water absorption is enhanced when rehydration solutions combine two to three different transportable carbohydrate substrates (glucose, sucrose, fructose, or maltodextrins) as opposed to solutions containing only one transportable carbohydrate substrate. The addition of a second or third carbohydrate substrate seems to activate additional mechanisms for intestinal solute transport and involve transport by separate pathways that are noncompetitive.
Carbohydrate Intake After Exercise:
- The restoration of muscle and liver glycogen stores is important for recovery after strenuous training. Consuming carbohydrate shortly after exercise enhances the rate of muscle glycogen synthesis.
- Several things contribute to glycogen repletion after exercise:
-Blood flow to the muscles is much greater immediately after exercise
-Muscle cells are more likely to take up glucose
-Muscle cells are more sensitive to the effects of insulin during this time period, which promotes glycogen synthesis.
- Glucose and sucrose are twice as effective as fructose in restoring muscle glycogen after exercise.
Recommended Carbohydrate Intake After Exercise:
After hard exercise>90 minutes:
1.5g carbohydrate/kg immediately after exercise
Additional 1.5g carbohydrate/kg 2 hours later
Protein Intake Before, During and After Exercise:
- You need protein for muscle growth and to repair muscle damage after exercise. You also need protein to make red blood cells, which move oxygen to muscles, and white blood cells, which help fight infection. Your body uses protein to make hormones and enzymes, which help regulate metabolism.
- Consuming some protein before a workout lasting 90 minutes or longer may help prevent muscle catabolism and reduce muscle fatigue/soreness.
-Consuming protein after a workout does not appear to increase the uptake of glycogen into cells provided that carbohydrate is consumed. It does, however, aid the recovery of muscle tissue by supporting muscle anabolism and minimizing muscle fatigue and soreness.
Recommended Daily Protein Intake:
1.2-2.0 g/kg/day with higher levels consumed during pre-race and racing seasons
Nutrient-dense sources of protein: fish, lean red meat, poultry, lean pork, eggs, soy products, edamame, yogurt, milk, legumes, beans, nuts
Fat Intake Before, During and After Exercise:
- You need fat for energy. Fat also helps your body to use some vitamins as well as plant chemicals known as “phytochemicals. Fat helps move substances in and out of cells, and it helps keep your brain and nervous system healthy. Choose heart-healthy fats like canola oil, olive oil, peanut butter, oil-based salad dressings, avocados, and nuts.
- Plan to eat fats primarily following endurance events rather than before or during.
Recommended Daily Fat Intake:
0.8-2.0g/kg/day to match energy expenditure