Athletes' CHO Intake PDF

Athletes: Energy Balance, Macronutrients and other Nutritional issues..  Readings Mandatory reading: ACSM/ADA/DC. (2016) Joint Position Statement on Nutrition and Athletic Performance Note: Many of the images with “blue” coloring have been taken by the book entitled Spor...

Athletes: Energy Balance, Macronutrients and other Nutritional issues..  Readings Mandatory reading: ACSM/ADA/DC. (2016) Joint Position Statement on Nutrition and Athletic Performance Note: Many of the images with “blue” coloring have been taken by the book entitled Sports Nutrition by Asker Jeukendrup (Human Kinetics)  Athlete nutrition 1. Total energy intake 2. Macronutrient intake a. CHO b. Fats c. Proteins 3. Micronutrient intake 4. Water intake 5. Recommendations for weight loss/gain  1. Total energy intake Needs can be quite variable in athletes – Should consider recommendations relative to body size and energy expenditure. Exceptionally high expenditures in some sports (e.g. Tour de France) Challenges for weight gain and weight loss  2. Macronutrient intake General considerations (Health Canada) – Relative vs. absolute! In general, similar to recommendations for all Canadians  2.a. Macronutrient intake (CHO) Review: Acute effect of endurance exercise High intensity exercise (~75% VO2max; 1 hr) depletes liver glycogen 50%. Supramax, repetitive work also depletes Time to exhaustion directly related to resting glycogen stores Effect of endurance-training glycogen-sparing improved mitochondrial metabolism enhances lipid oxidation larger glycogen stores in skeletal muscle  2.a. Macronutrient intake (CHO) About 12-16 g of CHO per kg of muscle. If someone has 25 kg of muscle = 300-400 g of CHO Liver glycogen… higher concentration than muscle but lower total amount (~100g) can be depleted to below 20g after an overnight fast  2.a. Macronutrient intake (CHO) Muscle stores: Intensity vs. duration Hepatic glucose production Intensity vs. duration Figure 6.1 Figure 6.2 Figure 6.4 Jeukendrup (Human Kinetics book)  2.a. Macronutrient intake (CHO) 1. General CHO intake guidelines 2. CHO days before competition 3. CHO hours before competition 4. CHO during competition 5. CHO after competition … first: glycemic index (GI) glycemic load (GL)  2.a. Macronutrient intake (CHO) 1. Glycemic index – pure glucose is the standard reference (100) 2. What can influence the GI of a food? 1. the biochemical structure of the carbohydrate 2. the absorption process, 3. the size of the food particle, 4. the co-ingestion of fat, fiber, or protein  2.a. Macronutrient intake (CHO) GI = AUC 50g other CHO ×100 GlycemicGlycemic IndexIndex (GI) AUC 50g glucose 9 GI: 0-100 Plasma Glucose 8 50g is standard (mmol/l) 7 Glucose 6 Other 5 GI affected by biochemical 4 structure of CHO, Pre 30 60 90 120 absorption, co-ingestion of Time (min) fat/protein/fiber. Glycemic load (GL) = GI × g CHO 100  2.a. Macronutrient intake (CHO) Examples Glycemic Index (GI) Low GI 70 corn flakes, baked potato, some white rices (e.g. jasmine), white bread 2.a. Macronutrient intake (CHO) General recommendations (ACSM 2016) -Daily needs  2.a. Macronutrient intake (CHO) 2. CHO days before competition Goal: to replenish/maximize muscle glycogen SUPERCOMPENSATION (CHO loading) – ↑ time to fatigue by 20% – ↓ time to complete task 2-3% – Mostly for activities > 60-90 minutes Other things to consider… – 5-7 days supercompensation not always feasible – If each g of CHO is store with 2-3 g of water… 2.a. Macronutrient intake (CHO) Carbohydrate loading - some studies suggest muscle glycogen doubled compared to “normal” resting levels! Classical More modern Any potential issues with classical supercompensation? hypoglycemia when CHO is low may not be not practical (meal prep) GI problems Mood Tenseness without training  Randomized to 5 days of high (70%) vs low CHO (55%) carbohydrate Exercise session – 75% for 1h Then did a muscle biopsy Also did time to fatigue at 85% of max  2.a. Macronutrient intake (CHO) Carbohydrate loading – Men vs. Women??? – High = 75%, low = 55-60% Men Women Tarnopolsky (1995)  Why might glycogen stores be different? Women tend to have a greater reliance on fat oxidation. Carb loading may increase weight – issues? If carb loading is not increasing muscle glycogen, where does it go?  2.a. Macronutrient intake (CHO) Carbohydrate loading – Muscle vs. liver glycogen Muscle glycogen is often super- compensated before full recovery of liver glycogen (muscle takes precedence – Fructose (fruits/honey) vs. glucose (pasta) Fructose can lead to slower muscle glycogen but similar liver glycogen replenishment. – Glycemic index??? High vs low  2.a. Macronutrient intake (CHO) 3. CHO hours before competition – Goal: to replenish/maximize liver glycogen and increase glucose delivery to muscle – 0-4 hrs before exercise: – Meal 3-4 hour before exercise can increase muscle glycogen. – 1 hour before liver glycogen can be increased (but likely not muscle) – 1.0-1.2 g/kg snack 30-60 min before exercise (more controversial but recently more accepted) Concerns over “reactive hypoglycemia” (which may be less common if consumed closer to exercise (e.g. 15 min) or if warm up is included. Consequence of excessive insulin released which continues past eating.  2.a. Macronutrient intake (CHO) 3. CHO hours before competition ~200-300g 3-4h before exercise some confusion due to glucose-induced insulin release (hypoglycemia, excessive skeletal muscle uptake and blunted lipolysis) Low GI vs High GI to minimize reactive hypoglycemia? Fructose (slower absorption – requires conversion in liver) may not be as effective….. Continued controversy Timing goal: not feeling hungry or undigested food in stomach More benefits if CHO cannot be consumed during exercise Individuality “GI distress”  2.a. Macronutrient intake (CHO) Comparing low vs. high GI meals 3h before endurance running @ 70% until exhaustion. 2g/kg body mass, GI 77 vs. 37, isocaloric (Meal taken 3 hr prior to exercise) Wu (2006) 2.a. Macronutrient intake (CHO) Running to exhaustion at 70% VO2max 108.8 ± 4.1 vs. 101.4 ± 5.2 min (P = 0.038) Increased fat WHY??? oxidation during exercise after LGI! Wu (2006)  HGI: Glucose higher PP but HGI: Insulin higher PP but lower during exercise. similar during exercise. HGI: FFA lower during. exercise HGI: fat oxidation lower. during exercise 2.a. Macronutrient intake (CHO) CHO before competition – needs to be tailored to the needs of the athlete and competition. Always test out in advance of the competition……  2.a. Macronutrient intake (CHO) 4. CHO during competition ~ 30-60 g/hr, could be up to 90 g/hr(liquid or solid) benefits high intensity, long duration work (extends time to exhaustion) – 0.7g/kg/hr training state does not improve ability to utilize oral CHO Better to provide every 15-20 min than after 2 h Not high fructose (slower to absorb, more GI symptoms) Controversy for events lasting 65% High GI if rapid 4-6 hours if speedy of daily EI replenishment recovery is needed required