nutrition for exercise
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Nutrition for Exercise
What is Nutrition ?
Science involving study of food and liquid requirements of the body for optimal functioning
Nutrients
Macronutrients Carbohydrates
Monosaccardides- Glucose, Fructose, galactose
Disaccharides- Sucrose, Lactose, Maltose
Polysaccharides• Plant• Animal
Protein Complete Incomplete
Lipids Saturated Unsaturated
Micronutrients Vitamins
Fat Soluble Water Soluble
Minerals Essential Trace
Water
Carbs
Monosacchardides- • Glucose • Fructose• Galactose
Disaccharides• Sucrose• Lactose• Maltose
Polysaccharides• Starch• Fibre
What happened to your breakfast??
Carbs and energy
GlycolisisGlucogenesisGluconeogenesisGlucogenolysis
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.
FOOD ITEM GLYCEMIC INDEX
Cornflakes 121Instant mashed potatoes 120Whole wheat bread 100
Baked beans 70
Skim milk 46
White pasta (boiled) 45
Lentils (boiled) 36
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
Proteins
‘Building blocks’Complete- Animal –
Incomplete- plant
Lipids
Saturated
Unsaturated Monounsaturated
Polyunsaturated
Micronutrients
Vitamins Vital to release energy from food
Minerals Important in catabolism and Anabolism of
macronutrients
Athletes Iron, especially for women athletes Calcium.
Energy for Sport
Major Considerations
CHO & protein requirementsPre competition mealsFluid 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 2 6 x 2 32 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
404075
17 10
2085
204580
Preparation for Competition
In general Taper exercise, 50% CHO diet 1st 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)
Bergstrom, Hermansen, Hultman, & Saltin (1967)
Mixed diet Low Carb diet High carb diet
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
“Hitting the Wall”
Muscle glycogen lowLiver glycogen lowBlood glucose lowExtreme fatigueDizzinessHunger - hypoglycaemia
Post Competition
Depends on time and intensity50 - 75 g every 2 hours 500gLarge carbohydrate rich mealRestRehydrate
Muscle Glycogen SynthesisMuscle 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 BWPre 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% = dangerConsume 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 ratesof 1-1.2 L /hr with gastric volumes of 100 - 200 mL.
DRINK CHO(g/100 mL)
Na+(mEq/L)
K+(mEq/L)
Caffeine(mg/L)
Osmolality(mOsmol/kg)
10K 6.3 52 26 350
Coca-Cola 10.7 2 0 136.8 554
Cranberry juice 10-15 2 7 890
Dioralyte 1.6 60 20 ?
Exceed 6.0 21 3 250
Gatorade 6.0 21 3 280
Isostar 7.6 24 4 305
Orange juice 11.8 0.5 58 690
Sprite 10.2 5 0 695
Water 0 trace trace 0-20
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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