Carbohydrates and Exercise PDF

Carbohydrates and Exercise Learning Outcomes Discuss the types and sources of carbohydrates Explain the role of carbohydrates in energy systems during exercise Provide dietary carbohydrate recommendations and strategies for exercise performance Discuss the role of ergogenic aids Carboh...

Carbohydrates and Exercise Learning Outcomes Discuss the types and sources of carbohydrates Explain the role of carbohydrates in energy systems during exercise Provide dietary carbohydrate recommendations and strategies for exercise performance Discuss the role of ergogenic aids Carbohydrates: Structural Features Simple Carbohydrates Monosaccharides Simplest form of CHO Simple sugars Glucose, fructose, galactose Disaccharides Consists of two monosaccharides Lactose, sucrose, maltose Carbohydrates: Structural Features Complex Carbohydrates Oligosaccharides Consists of short chains of monosaccharide units Raffinose, stachyose, verbacose Polysaccharides Long chains of monosaccharide units Starch, glycogen, dietary fiber Carbohydrate Polymer Commonly used in sports gels Typically include simple sugars and glucose polymers maltodextrins, rice syrup, polysaccharides, oligosaccharides Sources of Carbohydrates Healthy sources Whole grain cereals, breads, pasta; fruits, vegetables, legumes Performance benefit Carbohydrates are the major muscle fuel source for high-intensity exercise Glycemic Index (GI) Ranking of food based on blood glucose response to reference food High GI: Evoke large increases in blood glucose Carrots, raisins, corn flakes, breads, rice cakes Low/Moderate GI: Evoke small/modest increases in blood glucose Yogurt, apples, dried fruit, lentils, beans Glycemic Index of Foods Practical use of Glycemic Index Pre-race/training Low to moderate best to build up glycogen stores, avoid glucose-insulin spikes, GI tolerability During race Moderate to high is best for sustained energy High Intensity Sports Carbohydrates are the dominant energy source for sports such as: Track and field Swimming Martial arts Tennis/badminton Gymnastics Weight lifting Regulation of Blood glucose Fates of Blood Glucose CHO intake influences liver and muscle glycogen stores Glycogen levels affect endurance performance Decreased glycogen hasn’t shown a decrease in performance time but does show increases in the perception of fatigue.  Carbohydrate and exercise Exercise Intensity Exercise Duration How do athletes increase their muscle glycogen stores? Two techniques: 1. Depletion/repletion 2. Modified moderate approach Depletion/repletion Depleting glycogen reserves as much as possible through A combination of an extremely long bout of exercise about 7-10 days prior to a major competition, followed by a few days on a very low-CHO diet. Another bout of exercise on the 4th day and then 3 days of a high CHO diet. Modified Approach More popular approach is to taper training the week before competition while increasing the %CHO in diet (e.g. from 50-60% up to 70-75%) Although increases in muscle glycogen are not as dramatic as with the depletion/repletion approach, increases of perhaps 20% are possible (300 g 350 g) Carbohydrate Loading Carbohydrate loading is a fueling strategy designed to help athletes prepare for high-endurance activities Consider carbohydrate loading before periods of intense training or a long endurance event If you’re exercising at a steady pace and intensity carbohydrate loading can increase endurance by about 20% Carbohydrate loading ◦3 days of high CHO diet before race or long distance training session ◦Events longer than 60-90 minutes ◦ Muscle glycogen stores can be greatly increased, often by as much as 50% over the usual “full” condition (e.g. from 300 over 400 grams). Goal: Pre-training/race build up glycogen stores to prevent “bonking” or “hitting the wall” How to Carbohydrate Load Two Different Carb-Loading Example: Approaches Regimen 150-lb (68-kg) athlete 3–4 days prior 3.6–5.5 g carbs per lb 540–825 g carbs per day (Taper exercise for body weight daily for 3–4 days before 3–4 days before (8–12 g per kg) your event) 1–2 days prior 4.5–5.5 g carbs per lb 675–825 g carbs per day (Rest for 1–2 days body weight daily for 1–2 days before before your event) (10–12 g per kg) 600-grams carbs-per-day sample menu Benefits of carbohydrate loading Increases time to exhaustion Reduces the time to complete a task May improve performance in team sports that involve intermittent exercise and skill executions The downside to CHO loading/muscle glycogen supercompensation Only good for a one-time ultra distance event (marathon) Every gram of CHO is stored with ~4 g of water. This means that the storage of 500 g of CHO is accompanied by a water weight gain of approximately 2 kg. This would not be good for sports where an increase in body mass is not desirable. Dietary Carbohydrate Intake Recommendations CHOs should constitute from 45 to 60% of daily energy intake in the diet of an adult man, and more than 60% in the diet of an athlete In both recommendations, 80-90% of carbohydrate energy should come from complex carbohydrates In such cases, the mean CHO intake amounts from 6-8 g/kg of body mass, and during CHO loading up to 10 g/kg of body mass Carbohydrate requirements for Athletes Athletes need to consumes approximately 325-625 g CHO The daily recommended intake for athletes 5-10 g of CHO/kg of body weight Eg: 70 kg = 350-700g CHO (1400-2800 kcal) This is 60% of a 2500 kcal - 5000 kcal diet (athlete in training) A recommended tennis match carbohydrate intake regimen Before exercise Regular training = 5–7 g/kg High training/tournaments = 7–10 g/kg During match 30–60 g OR 500–1000 ml/h common carbohydrate sports drink After match Within an hour of exercise = 1.5 g/kg Carbohydrate intake before exercise Goal: maximize exercise performance 3-5 hours: breakfast Large meal to replenish liver glycogen Increase muscle glycogen stores Carbohydrate intake before exercise 60-30 minutes before exercise Top off liver glycogen Increase blood glucose levels, can be used as a substrate during exercise...or if intensity is low enough it will be used to synthesize muscle glycogen. Q. Common belief: ingesting High GI CHO right before exercise will create rebound hypoglycemia and decrease performance. Why? To prevent rebound hypoglycemia in athletes Consume lower GI CHO one hour before exercise If high GI CHO is consumed right before or at the onset of exercise, then there seems to be a benefit to maintaining carbohydrate intake during exercise. Carbohydrate intake during exercise CHO consumption during exercise >45min can improve performance by: Maintaining blood glucose and CHO oxidation rates Sparing liver glycogen Synthesizing muscle glycogen during LOW intensity exercise Increasing motor skills in prolonged periods of play How much CHO to consume during exercise 1.2g CHO per minute, 70g/hour during endurance exercise What to drink? glucose polymer (gatorade=good) galactose, fructose-not so good Choose drinks ranging from 4-8% CHO. Remember that CHO replacement during exercise is not generally needed for activities lasting less than 90 minutes. Carbohydrate intake after exercise GOAL: To replenish muscle glycogen The rate of glycogen synthesis depends on glucose transport to the muscle and the enzymes involved in glycogen synthesis. Exercise increases: - GLUT 4 (transporters) - glycogen synthase Factors affecting glycogen synthesis Timing When CHO is delayed two hours muscle glycogen is 45% lower compared to immediate consumption of the same amount. Rate of ingestion (amount): 0.7-1.0g CHO/kg consumed every two hours Type (High GI, vs. Low GI): High GI, large insulin release, more CHO storage Combination with protein Training and game/race day Training and race day diet should consist of: CHO: 55-70 % (6-10 grams per kilogram of body weight or 8-10 kcals per kilogram) Fats: 25-30% Protein: 12-15% (1.0-1.5 g/kg) of high quality protein Carbohydrate snacks Foods supplying 50 grams CHO 1 sports bar (check label) 500 ml juice 1.3 bagels 3 medium pieces of fruit 1/2 cup dried fruit 1 honey sandwich 2 breakfast bars 1 cup white rice 1 baked potato *Average 70 kg endurance athlete should consume 560 grams CHO per day Refueling during Exercise: Role of Carbohydrates Carbohydrate is the primary muscle fuel utilized during exercise, and stores are limited Carbohydrate refueling needs depend on the length and intensity of exercise For long-duration, all-out effort: refuel with sports nutrition products that provide a 2:1 blend of glucose and fructose to enhance energy delivery to muscles and help prepare for high- endurance activities CHO refueling Recommendations during exercise Exercise lasting less than Carbohydrate intake during exercise is not required to fuel your 1 hour performance However, a sports drink with carbs and sodium can help hydrate you more effectively under hot and humid conditions Exercise lasting Consume 30–60 g carbs during each hour of exercise to boost 1–2 hours performance and help prepare you for high-endurance activities Intense training lasting Consume 45–90 g of a 2:1 blend of glucose and fructose per hour of longer than 2–3 hours exercise to increase energy delivery to muscles and help prepare you for high-endurance activities Summary of the advice for CHO intake during endurance events of different durations To promote full recovery after exercise The necessary nutrients need to be provided: Carbohydrates to restore depleted glycogen stores Protein to repair and build muscle tissue Fluids and sodium to rehydrate CHO in promoting full recovery after exercise To speed glycogen restoration after strenuous exercise: Consume 0.5 grams of CHO/lb (1.1 g/kg) body weight within 30 minutes of finishing exercise For a 150-lb (68-kg) athlete, that equates to 75 g of CHO right after exercise Repeat this within 2 hours after exercise, or consume a CHO-based meal For heavy training, repeat this hourly for the first 3 hours after exercise, or consume CHO-based meals and snacks Simple CHO right after exercise are more effective at speeding glycogen restoration. This is especially important if you are exercising again within 24 hours Promoting full recovery after exercise Total Daily 150-lb (68-kg) Exercise Carbohydrate Needs Athlete Light 4 hours, 4.5–5.5 g per lb 680–816 g of carbs moderate- to high- body weight (10–12 g per kg) per day Training intensity Promoting full recovery after exercise Sample intake for about 500 g carbs per day Grams of carbs 1 cup cereal, 1 cup milk 45 1 cup blueberries 21 PowerBar® Sport Energy™ bar 43 Sandwich, 2 oz turkey 32 1 cup baby carrots 12 16 oz chocolate 1% milk 52 1 cup flavored yogurt 47 BBQ chicken tenderloins, 7.5-oz package 34 1 cup white rice 41 1 cup cooked sweet potatoes 58 1 PowerBar® Harvest Energy™ bar 35 16 oz cranberry juice 68 PowerBar ProteinPlus® protein powder drink mix (1 serving) 7 Total grams of carbs 495 Food values — USDA database. PowerBar values based on analysis. Sports drinks for endurance exercise Recommended for activity > 60 minutes ◦ Help maintain blood glucose level and blood volume ◦ Delay “bonking” Supply electrolytes: Na, K, P, Cl