Carbs and energy Glycolisis Glucogenesis Gluconeogenesis Glucogenolysis Energy! (ATP) -Glucose Glycogen- ST storage
Glycaemic Index Index for comparing the blood glucose response from the ingestion of different foods. - The more complex the carbohydrate, and the more fat, protein and fiber in the food lower glycaemic index.
Whole wheat pasta Glucose White breadIngestion Note the differences in the area under the curve Note that the blood glucose response to white bread is the standard reference
Major Considerations CHO & protein requirements Pre competition meals Fluid replacement
Daily intake Normal people 1500—2500 calories 50-60% carbs 20-30% fat 15-20% protein Athletes 1400 (gymnasts) – 6000 (TDF cyclists) 70-80% carbs 20% fats 10% protein
RDI’s- Protein Sedentary people and recreational athletes have similar protein requirements Sedentary: 0.8 to 1 gram of protein p/kg BM. Athletes: 1.2-1.8 g protein p/kg BM 87 kg x 1.8 g or 87 kg x 1.2g = 104.4 - 156.6 g p/day 8 28.5 x 26 x 232 x 2
RDI’s- Carbs Depends on sport Normal people: 5 g/kg Endurance athletes (training > 60 min p/day: 8-10 g /kg 59 kg x 8 g = 472 g p/day 20 465 40 75 1710 2085 20 4580
Preparation for Competition In general Taper exercise, 50% CHO diet 1 st 3 days V. low exercise, 80% CHO diet 3 days prior Strict protocol Depletion Day 1- Exhaustive exercise Day 2,3,4 mod intensity training & low carb intake (100g p/day) Day 5,6,7 High CHO intake (400-700g)
Day of Competition Nutrition 1-4 hours before= Large CHO meal 150 – 300g carbohydrate (3-5g CHO p/kg BW) OR 4 hours before – meal (200 g CHO) 1 hour before- snack (100g CHO)
CHO ingestion every 20 min CHO ingestion late in exercise No CHO ingestion 65-75% VO2max
Liquid Carbohydrate Ingestion Suited for long duration (> 60 min) exercise where a glucose source is needed to support blood glucose Need at least 45 g/CHO/Hr Drink of 60 g CHO/L would require at least 750 mL/Hr During hot and humid conditions, a lower [CHO] drink would allow greater volumes to be ingested. Most people can not ingest more than 1.2 L/Hr CHO should be mostly glucose
Post Competition Depends on time and intensity 50 - 75 g every 2 hours 500g Large carbohydrate rich meal Rest Rehydrate
Muscle Glycogen Synthesis Muscle glycogen is synthesized very slowly. The rate of synthesis differs depending on the prior exercise conditions, after low intensity exercise - 7-9 mmol/kg/Hr after high intensity exercise - ~ 15 mmol/kg/Hr Muscle glycogen synthesis is optimized when, there has been no exercise-induced muscle damage recovery is passive at least 0.7 g CHO/kg/Hr is ingested ingestion occurs as soon after exercise as possible glucose should be the predominant CHO and the source food should have a high glycemic index
Tour de France riders Require CHO intake of 13 g/kg BW Pre competition meal Breakfast 3 hours before start High Carb (100g) snack Energy bars/ energy drinks 1 hour before start During the race Glucose gels- 15g CHO
Liquids - Rehydration Sweat rates increase with intensity of exercise Fit people sweat more and sooner; and it is more dilute Can be up to 1- 2.8 L/hr Sodium (Na), Potassium (K), Magnesium (Mg), Chlorine (Cl) Loss of body weight > 3% = danger Consume 500-1000 ml per hour
Fluids- Gisolfi & Duchman, 1992 Before: <1 hr @ 80-130% Vo2max= 300-500ml liquid w/ 30-50g CHO >1 hr @30-90% Vo2 max= 300-500ml H20 During <1 hr @ 80-130% = 500-1000ml H2o 1-3 hr @60-90% =800-1600ml liquid + 6-8% CHO + Na and Cl >3 hr = 500-1000ml H20 + 6-8% CHO + NA and Cl After Continue H2o consumption Caffeine, energy drinks and alcohol further dehydrate Gisolfi, C.V., & Duchman, S.M. (1992). Guidelines for optimal replacement of beverages for different athletic events. Medicine and Science in Sports and Exercise. 24, 679-687.
Gastric emptying Maximal rates of 1-1.2 L /hr with gastric volumes of 100 - 200 mL.
Nutrient and electrolyte content of commercial drinks.
Important nutrients & fads Female Athlete Triad Steroid use/abuse Over-consumption proteins Muscle building powders Creatine
Fad Diets Low CHO Atkins, Zone, South Beach Depletes glycogen, “eats” muscle and reduces performance Relies on ketosis Bad breath Starvation Body conserves fat stores Lose h20 only Diet pills Fat metabolisers do not exist Placebo effect Legal action against diet companies
Summary Sports nutrition has a huge impact on performance Nutrition and rehydration account for huge gains Expensive pills, potions and fads account for minute gains if any at all Avoid fads as many are counterproductive and may be illegal, banned substances
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