IB Sports, exercise and health science A.2.2.2 Nutritional Strategies for Exercise and the Effects of Low Energy Availability Notes

Nutrition Strategies

Pre-Exercise Nutrition Strategies

1. Pre-exercise nutrition plays a critical role in enhancing performance during both endurance and high-intensity activities.
2. Proper fueling before exercise helps optimise energy availability, delay fatigue, and enhance recovery.

Carbohydrate Loading

1. Carbohydrate loading enhances endurance performance by ensuring sufficient energy is available for prolonged physical activity.
2. Glycogen is stored in muscles and liver and is the primary fuel used during aerobic activity.
3. By carbohydrate loading, athletes can increase their glycogen stores beyond normal levels.
4. A well-conducted loading protocol ensures a maximal glycogen reserve, helping prevent early fatigue and maintaining energy levels throughout the event.

Phases of Carbohydrate Loading

1. Depletion Phase: Involves a reduction in carbohydrate intake and intense exercise (usually about 3-4 days before the event) to deplete glycogen stores.
2. Loading Phase: A high-carbohydrate diet (typically 7-12 g per kg body mass per day) over 24-72 hours combined with reduced training drives supercompensation of glycogen stores.

Glycogen Depletion in Different Fibre Types

1. Slow-twitch (type I) fibres: Dominant at low-to-moderate intensities. Deplete first during long endurance work.
2. Fast-twitch (type II) fibres: Recruited as intensity rises. Emptied quickly by all-out anaerobic efforts.
3. Specificity rule: ~30 seconds of maximal cycling can substantially reduce fast-twitch glycogen even though slow-twitch may remain full.

Timing and Composition

1. The timing and composition of your pre-exercise meal can affect energy levels, glycogen availability, and overall performance.
2. The type of carbohydrate consumed, whether low or high GI, can also affect energy release during exercise.

Low GI vs High GI Carbohydrates

1. Low-GI Carbohydrates (e.g., whole grains, fruits) are digested more slowly and provide a steady release of glucose, helping to sustain energy levels during prolonged exercise.
2. High-GI Carbohydrates (e.g., white bread, potatoes, sugary foods) are rapidly digested and cause a quick spike in blood glucose and insulin, providing immediate energy for short bursts of intense exercise.

Glycemic Index (GI) for Recovery

1. Ranks foods by how fast 50 g of their carbohydrate raises blood glucose, with pure glucose set at 100.
2. High-GI foods: Sugary drinks, white rice, sports bars. Best choice for rapid post-exercise recovery when another session is within 24 hours.
3. Low-GI foods: High-fibre cereals, peanuts, raw fruit and vegetables. Better for sustained pre-exercise meals.

Timing

1. Ideally, a pre-exercise meal should be consumed 2-3 hours before exercise to allow time for digestion.
2. A meal high in carbohydrates, moderate in protein, and low in fat helps provide adequate fuel without causing digestive discomfort.
3. If eating closer to exercise (30 minutes to 1 hour), focus on high-GI carbohydrates for a quick energy boost.

Daily Protein Requirements

1. Healthy adult baseline: 0.8 g protein per kg body mass per day.