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Overview: Carbohydrates. Importance of carb storage Muscle & liver How many carbs are right for you? What to eat before, during and after exercise to enhance performance. Glycogen. The way the body stores glucose Limited storage Stored in muscle & liver
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Overview: Carbohydrates • Importance of carb storage • Muscle & liver • How many carbs are right for you? • What to eat before, during and after exercise to enhance performance.
Glycogen • The way the body stores glucose • Limited storage • Stored in muscle & liver • Important to have adequate stores because glucose is used for: • Fuel in the anaerobic and aerobic system • Fat can only be used as fuel in aerobic system if glucose is available.
Glucose stored in 3 locations • Muscle glycogen • Major source of glucose for the muscle • Provides 1200-1600 calories • Liver glycogen • Provides 300-400 calories • Glucose in blood • Provides 100 calories
Glycogen Depletion • Occurs during prolonged endurance exercise • Can be gradual, occurring over repeated days of training. Glycogen stores decrease each day • Workouts become difficult and fatigue is common.
Decline in Glycogen Stores Progressive decline due to inadequate carbs (< 50% of total calories) pg. 82 LAM book
Glycogen Stores & Endurance • Strong connection between muscle glycogen and length of time to exhaustion. • Study: 3 groups of runners eating different diets for 3 days. • High fat diet – < 5% calories from carbs • Mixed diet – 50% calories from carbs (typical American diet) • High carb diet – 82% calories from carbs
Why greater endurance on a high carb diet? • Increases glycogen stores • 3 days of high carb diet- plenty of glucose stored as glycogen. • Adequate glycogen storage before exercise • Delays fatigue • Contributes to endurance
Challenge Question Studies show that runners who eat a mixed diet (50% carbs, 25% fat, 25% protein), can exercise for approximately ______ minutes until exhaustion. • 90 minutes (1 ½ hours) • 120 minutes (2 hours) • 150 minutes (2 ½ hours) • 180 minutes (3 hours)
How many carbs do you need? • Determined by weight and exercise • Weight: Endurance and strength training recommendation is between 6-10 grams carbs per kg body wt. • Weight ÷ by 2.2 = kg
How many carbs do you need? • Determined by duration or intensity: • 1 hour or low intensity: 6 g/kg/daily • 2 hours or moderate intensity: 8 g/kg • 3 hours or heavy intensity: 10 g/kg
Determine Your Carb Needs How many grams of carbohydrates do you need daily to maintain your glycogen stores? • Determine your weight in kilograms • Weight divided by 2.2 = kg • Determine your exercise duration or intensity • Multiply the numbers • Experiment with consuming this amount of carbohydrates. Make adjustments.
Carbs: % vs Grams • 6-10 g/kg/day takes into account body wt. • More accurate & practical to consume a specific amount of grams from carbs rather than a % of calories • 60 kg athlete eats < 2000 cal/day, a diet of 60% calories from carbs (4-5 g/kg/day) will not maintain optimal glycogen stores.
Eating Before Exercise • High carb diet on a daily basis helps maintain adequate glycogen storage • With adequate glycogen, exercise lasting <90 minutes (moderate, intermittent or high intensity), no benefit for carbs prior to event. • High carbohydrate meal the night before event helps maximize glycogen stores • Choose a familiar food
Eating Before Exercise, cont. • Morning practice or event: • Exercise > 1 hour: eat small high carb meal at least 1 hour prior (limit fat, protein, fiber) • Afternoon practice or event: • Best to eat lunch 3-4 hours prior • Eating within 2 hours of exercise, limit fat, protein, fiber • Important not to be digesting food during exercise. • Experiment with pre-exercise meals to determine what works best.
Carbs During Exercise • Important if exercise lasts > 1 hour • Helps maintain blood glucose & spare glycogen • Ability to absorb carbs limits intake. The body can absorb: • 0.5-1 gram carb/minute • 30—60 g. of carbs/hour
Carbs During Exercise • The body can absorb & burn carbs at rate of: • 0.5-1 gram carb/minute • 30—60 g. of carbs/hour • Carb amounts above this my cause nausea, cramping or diarrhea. • Can obtain 30-60 g. from food (fig bars, gels, energy bars) or sports drinks.
Sports Drinks During Exercise • Sports drinks provide carbs and fluids • Best because they provide 6-8% carbohydrate • Gatorade is 14 grams of carbs per 8 ounces • Do not drink juice (11% carbohydrate) • Juice is 27 grams carbs per 8 ounces • Contributes to cramping, nausea and diarrhea • The body can absorb 30-60 grams/hour • Gradually drink approx. 24 ounces (3 c.) per hour • Ex. Gatorade: 24 ounces per hour = 42 grams
Post Exercise Recovery • Adequate glycogen storage is critical for continual optimal performance. • Replacing glycogen stores after strenuous training (2+hrs) helps minimize fatigue. • Within 2 hours, glycogen is restored at 8%/hr. Afterwards, it drops to 5%/hr. • It takes 20-22 hours to replace glycogen.
Post Exercise Recovery • Within 30 minutes of exercise: • Best to consume carb drink - chocolate milk or sports drink • Sucrose and glucose are better at restoring glycogen than fructose from fruit • Within 2 hours of exercise: • Consume high carb meal – pasta, bread, rice • Important to consume 6-10 grams per kg body weight every day.
