Exercise Physiology - Chapter 3 - Optimal Nutrition for Physical Activity

Recommended Proteins

• recommended dietary allowance equals 0.83gxkg body mass-1

• athletes who train intensely should increase intake to 1.2 to 1.8kg body mass-1

Recommended Lipids

• no standards exist for optimal lipid intake

• lipid intake should not exceed 30-35% of the diet’s energy content

• at least 70% should be unsaturated fatty acids

• limit saturated fat intake to less than 7% of total daily kcal intake

• limit trans fat intake to less than 1% of total daily kcal intake

High-Fats Diets

High-fat diet produced suboptimal adaptations in endurance performed not fully remedied by switching to a high-carbohydrate diet

Recommended Carbs

• recommendations range between 6 and 10 gxkg-1xd-1, depends on level of activity

• a low carbohydrate diet rapidly compromises glycogen reserves for vigorous physical activity and intense training

• optimum intake varies with daily energy expenditure and type of exercise performed

• the diet of physically active persons should contain 55-60% carbohydrates, predominantly from fiber-rich, unprocessed grains, fruits, and vegetables rP

Precompetiton Meal

• if a person trains or competes in the afternoon, breakfast becomes the important meal for optimizing glycogen reserves

• should contain 150-300g of carbs, 3 to 5 gxkg body mass as either solid or liquid

• contain relatively little lipid and fiber to facilitate gastric emptying and minimize gastrointestinal distress

• consume food 1-4 hours prior to event

Energy Beverages and Sports Drinks

• Limit energy beverage consumption to no more than 500mL or 1 can daily

• Do not mix energy beverages with alcohol - this can mask intoxication and is dehydrating

Carbohydrate Feedings Prior to, During, and in Recovery from Physical Activity

• Pre-exercise: Should be ingested at least 60 minutes before

• During exercise: 60g of liquid or solid carbohydrate hourly benefits intense, long duration (less than 60 mins) aerobic activity and repetitive brief bouts of near max exercise.

• Post exercise: Consuming carbohydrate-rich, high glycemic foods within 15 minutes following intense training or competition speeds glycogen replenishment

The Glycemic Index and Pre-Physical Activity Feedings

• Measure of blood glucose increase after consuming a specific carbohydrate food

• Foods with a low glycemic index digest and absorb at a slow rate to provide a steady supply of slow-release glucose during prolonged exercise

Glucose Feedings, Electrolytes, and Water uptake

• rate of gastric emptying (rate of contents of food exiting stomach and intestines) (dictate how fast we absorb nutrients) will affect fluid and nutrient absorption

• A 5-8% carbohydrate - electrolyte beverage consumed during exercise contributes to temp regulation and fluid balance as effectively as plain water.

Recommended Oral Rehydration Beverages

• Optimal gastric emptying occurs by consuming 400-600mL of fluid immediately before exercise followed by regular fluid ingestion during exercise (250mL every 15 min)

• A moderate amount of sodium added to rehydration fluid stabilizes plasma sodium concentrations to minimize hyponatremia risk

• each pound of weight loss corresponds to 450mL/15oz of dehydration