Detailed Notes on Enhancing Performance Through Nutrition and Hydration

Nutrition and Hydration Strategies

Fluid Replacement

  • Humans lose water through breathing, sweating, and urination.
  • To prevent dehydration (fluid loss exceeding intake), consume approximately 2L of fluids daily.
  • Urine color indicates hydration levels: clear urine signifies good hydration, while darker urine suggests dehydration.

Pre-Exercise Fluid Replacement

  • Increase fluid stores before an event.
  • Recommended: 1L of fluid prior to exercise.
    • 600ml, 3-4 hours before.
    • 400ml just before to prime the stomach.
  • Avoid caffeinated drinks due to their diuretic effect.
  • Benefits: Allows more sweating before performance is inhibited.
  • Drink approximately 200ml of water every 15 minutes during activity, adjusting for environmental conditions and exercise intensity.
  • Avoid drinking only when thirsty, as you're likely already dehydrated.
  • Use sports drinks to replace salt lost in sweat, not just water.

Post-Exercise Fluid Replacement

  • Replenish to pre-exercise weight.
  • Consume 1.5L of fluid for every 1L of sweat loss, accounting for urination.
  • Consume slightly salty fluids to maintain osmolality and reduce urination.
  • Practical method to determine fluid replacement needs:
    1. Weigh yourself before exercise.
    2. Perform exercise.
    3. Weigh yourself after exercise.
    4. Each 100g of weight loss = 150ml of fluid to replace.
      • Example: 1kg weight loss requires 1.5L of fluid.

Fluid Replacement Guidelines

  • 24 hours prior: 3500ml.
  • 3-4 hours prior: 3000ml
  • 20 minutes prior: 400ml
  • Every 15 minutes during: 2500ml
  • Post Exercise: 500ml

Phase of Activity Considerations

  • Athletes need the right food combination during training to provide correct nutrients and fuel.
  • Consider the type of sport and environmental conditions.

Aerobic Events

  • Require a high amount of carbohydrates (CHO).
  • Use a combination of high and low Glycemic Index (GI) foods.
  • Consume adequate protein for muscle repair post-training.
  • Maintain adequate fluid intake.

Anaerobic Events

  • Power athletes need more protein than endurance athletes.
  • Require a high amount of CHO for training fuel.
  • Maintain adequate fluid intake.

Climatic Conditions

  • Increase fluid intake in hot conditions.
  • In cold environments, especially for endurance events, increased fat intake may aid insulation.

Pre-Competition Nutrition

  • Carbohydrate loading delays glycogen store depletion.
  • Increase CHO consumption before competition to store extra glycogen in the liver and muscles.

Three-Day Method

  • Consume approximately 7-8g/kg body weight of carbohydrates for 3 days before competition (approximately 700g stored).
  • Taper exercise to avoid depleting glycogen stores.

One-Day Method

  • Consume approximately 8-10g/kg body weight of carbohydrates the day before competition (approximately 700g stored).
  • Equivalent to eating almost 3 loaves of bread - supplements may be necessary.
  • Reduce training load to spare muscle glycogen stores.

Important Note on CHO Loading

  • 1 \, \text{gram glycogen} \, \text{binds with} \, 2.7 \, \text{grams} \, H_2O,
  • CHO loading 700 grams = 1.9kg H_2O = 2.6kg weight increase.
  • This weight increase might be detrimental if the extra CHO isn't needed.
  • As exercise intensity increases, CHO usage increases.
    • At 85% VO_2 max, 90% of energy comes from CHO.
  • Muscle glycogen, liver glycogen, and blood glucose can be depleted in 1.5-2 hours, depending on exercise intensity.
  • CHO loading pre-exercise and intake during exercise allows athletes to perform longer at higher intensity.
  • Beneficial for events lasting 1 hour or more.

Advantages of CHO Loading

  • Avoids depletion of glycogen stores by increasing muscle and liver glycogen levels.
  • Allows aerobic athletes to maintain higher intensity for longer.

Disadvantages of CHO Loading

  • Binding of H2O to CHO molecules increases H2O absorption, increasing weight.

Pre-Event Meal (1-4 Hours Before)

  • Provide adequate carbohydrates and ensure optimal hydration.
  • Consume low GI foods for slow glucose release into the bloodstream.
  • The body uses recently digested foods as an energy source, assisting glycogen sparing.
  • Examples: Pasta, all bran cereal, apples, lentils.
  • Consume approximately 600-800ml fluid 1 hour before the event to assist hydration.

Considerations

  • Food preference (liquid meals, nutrition bars).
  • Digestibility of foods (low in fat and fibre).

Advantages

  • Increase glycogen levels leading to glycogen sparing.
  • Ensure optimal hydration.
  • Ensure gastrointestinal tract feels comfortable during performance.

During Exercise Nutrition

  • CHO and fat are the most common fuels used by athletes.
  • Events lasting up to 60 minutes can be fueled by stored CHO and fat.
  • For longer events, CHO consumption is important to avoid glycogen depletion.
  • CHO ingestion prevents low blood sugar, crucial for brain function and avoiding CNS inhibition.
  • Important for team sports requiring decision-making and concentration.
  • Studies: Athletes make fewer errors when refueling during a game.
  • Consume 30-60g of High GI CHO per hour, or 1g/kg of body mass per hour.
  • Examples: sports bars, jelly beans.
  • Consume approximately 150-200ml fluid every 15 minutes to prevent dehydration.
  • Electrolyte drinks (5-8% CHO concentration) spare glycogen and prevent dehydration.
  • Avoid high fibre/fat foods, as they are hard to digest and may cause upset stomachs.

Recovery Nutrition

First 30 Minutes After Exercise

  • Muscles are most responsive to topping up glycogen stores immediately after exercise.
  • Increased muscle glycogen storage occurs due to high GI food consumption.
  • The more depleted CHO stores, the faster the rate of recovery.

Next 24 Hours After Exercise

  • Glycogen replenishment takes at least 24 hours after heavy endurance work.
  • CHO replenishment depends on exercise intensity and duration.
  • Consume low/medium GI foods for the next 24 hours to complete glycogen replenishment.
  • Protein is important for muscle repair.
  • Recommendations:
    • 1g/kg body mass of high GI CHO within 30 minutes of the event.
    • At least 7-10g/kg body mass of low to moderate GI CHO over the next 24 hours.
    • Protein consumption.
    • Consume fluid equating to 1.5 * weight loss.

Summary: Dietary Recommendations for Events Longer Than 90 Minutes

  • Day(s) before: CHO loading with exercise taper, maintain fluid intake.
  • Pre-event meal (1-4 hours before): 1L fluid, low GI meal.
  • During event: 200ml fluid every 15 minutes, 30-60g high GI CHO per hour.
  • Immediately after (first 30 minutes): 1g/kg body mass of high GI CHO, commence fluid replenishment (1.5 * weight loss).
  • Next 24 hours: Fluid (1.5 * weight loss), 7-10g/kg body mass low to moderate GI CHO, protein for muscle repair.