IB Sports, exercise and health science A.3.3.4 Hydration and Nutritional Strategies for Exercise Recovery Notes

Nutrition and Recovery

1. Recovery from training and competition depends heavily on what an athlete consumes after exercise, since post-exercise nutrition restores depleted fuel stores, supports tissue repair, and re-establishes fluid and electrolyte balance.
2. Nutritional planning must address both quantitative needs (total energy intake) and qualitative needs (the composition of macronutrients and micronutrients).
3. An athlete who consumes adequate calories but the wrong mix of nutrients will recover incompletely.

Macronutrient Intake for Recovery

1. Carbohydrates

1. Carbohydrates are the primary fuel source for the body, stored as glycogen in muscles and the liver.
2. Post-exercise carbohydrate intake is crucial for restoring glycogen levels and ensuring energy availability for future activity.
3. Glycogen resynthesis is the process of replenishing glycogen stores after exercise to restore energy balance.

Factors Affecting Glycogen Resynthesis

1. The first 2 hours after exercise is the critical window for glycogen replenishment, when muscle is most sensitive to carbohydrate availability.
2. Glycemic Index (GI): High-GI foods (e.g., white rice, bananas) promote faster glycogen recovery, while low-GI foods (e.g., oats, lentils) provide sustained energy.

Carbohydrate Quantification

1. The minimum intake rate to support glycogen replenishment is 0.7 g per kg of body mass per hour.
2. After prolonged intense exercise, full restoration of glycogen stores requires a daily intake of 8 to 12 g per kg per day.
3. Complete glycogen resynthesis typically takes about 24 hours when intake is adequate.
4. Foods with a high glycaemic index raise blood glucose quickly and accelerate glycogen resynthesis compared with low-glycaemic-index foods.
5. Carbohydrate drinks are advantageous because they contribute to rehydration at the same time as fuel replacement.

2. Proteins

1. Protein is essential for muscle repair, growth, and adaptation.
2. Exercise causes microtears in muscle fibers, which require protein for recovery.

Optimal Protein Intake for Recovery

1. Approximately 20 g of protein at a single feeding maximises muscle protein synthesis, and larger amounts at one sitting confer little additional benefit.
2. Complete proteins (e.g., whey, eggs, chicken) contain all essential amino acids needed for muscle repair.

Animal vs Plant Sources

1. Animal-based protein sources stimulate higher rates of muscle protein synthesis than plant-based sources.
2. The difference is attributed to the amino acid profile, particularly the leucine content, and to the rate at which the protein is digested and absorbed.
3. Athletes following plant-based diets can still meet protein requirements but may need higher total intakes or combinations of sources to match the response produced by animal protein.

3. Fats

Fats play a role in long-term recovery and inflammation control.

4. Creatine Monohydrate

1. Creatine is a naturally occurring compound that helps replenish ATP stores in muscles.
2. Creatine phosphate system provides a rapid source of ATP during short bursts of high-intensity exercise.

Benefits of Creatine for Recovery

1. Speeds up ATP replenishment: Enhances power output.
2. Reduces muscle damage and soreness: Aids faster recovery.
3. Short-term creatine supplementation may produce a small increase in water retention over the first days, but this is not observed over weeks of continued use.

Dosing and Tolerance

1. Recommended creatine supplementation is 3 to 5 grams per day, or approximately 0.1 g per kg of body mass per day.
2. At these doses, creatine is well tolerated by healthy individuals.
3. Short-term supplementation may produce a small water retention over the first days of intake, but this is not observed over weeks of continued use.

Safety

1. Creatine is not an anabolic steroid.
2. At recommended doses, creatine does not cause kidney damage or renal dysfunction in healthy individuals.
3. Current evidence does not support claims that creatine causes dehydration or muscle cramping.

Wider Recovery and Health Effects

1. Creatine may help maintain optimal glycogen levels in athletes who deplete glycogen heavily during training.
2. It may reduce muscle damage and enhance recovery from intense exercise.
3. It may reduce musculoskeletal injuries and accelerate injury recovery.
4. It may reduce the risk of heat-related illness when training in hot, humid environments by supporting hyperhydration and improved heat tolerance.

Exercise-Induced Muscle Damage and ROS

1. Exercise-induced muscle damage is the structural disturbance within muscle fibres caused by high-intensity exercise and eccentric muscle actions, and it presents as impaired force production, increased soreness, and reduced range of motion in the days that follow.
2. Free radicals are generated as a normal part of metabolism, and those derived from oxygen are termed reactive oxygen species (ROS).
3. During exercise, whole-body oxygen consumption can rise 20-fold above resting values, and within working muscle mitochondria the local increase reaches around 200-fold, generating substantial ROS as a by-product.
4. A controlled inflammatory response is part of the repair process, but when ROS production outstrips the antioxidant capacity of the tissue, redox balance is disrupted and oxidative stress develops, causing further damage and delayed healing.

5. Polyphenol-Rich Foods

Polyphenols are antioxidant compounds found in plant-based foods that help reduce oxidative stress and inflammation.

Polyphenol Supplementation Benefits

1. Plant-derived polyphenol supplements help reduce the negative effects of exercise-induced oxidative stress and accelerate recovery of muscular function.
2. A particular benefit is reduction of muscle soreness and faster recovery after exercise-induced muscle damage.
3. Polyphenol supplementation is most clearly effective in team sports that involve frequent high-intensity eccentric actions such as jumping and rapid changes of direction.

Foods High in Polyphenols and Their Benefits

Hydration After Exercise

1. Water makes up between 40 and 70 per cent of total body mass, around 65 to 75 per cent of muscle mass, and approximately 50 per cent of fat mass.
2. Maintaining body water is essential for thermoregulation, cardiovascular function, and the transport of nutrients and metabolic by-products.
3. Percent dehydration is calculated from body mass measured before and after exercise: ((weight before minus weight after) divided by weight before) times 100.
4. For an accurate result, the athlete should be weighed naked, dry, and with an empty bladder both before and after exercise.
5. Thirst is an insensitive marker of hydration status during exercise and does not respond quickly enough to keep pace with sweat losses.
6. Thirst is also blunted in cold environments and at high altitude, increasing the risk that fluid intake will be insufficient to match losses.

Importance of Electrolyte Balance

1. Electrolytes are essential minerals that regulate fluid balance, nerve signaling, and muscle contractions.
2. During exercise, sodium, potassium, and magnesium are lost through sweat, leading to muscle cramps and fatigue.

Rehydration Strategies

1. To account for ongoing sweat and urinary losses, athletes should aim to consume approximately 150 per cent of the fluid lost during exercise.
2. Each kilogram of body mass lost corresponds to approximately one litre of fluid.
3. Rehydration fluids should contain 20 to 50 mmol per litre of sodium, because plain water alone reduces the osmotic concentration of the blood and increases urinary excretion.
4. 3 to 12 per cent glucose in the drink increases fluid retention by supporting sodium uptake and intestinal water absorption.
5. Spreading fluid intake over 4 to 5 hours produces a better overall fluid balance than rapid replacement within 3 hours or less.
6. Caffeine and alcohol may increase urine output relative to water or electrolyte drinks, making them less effective rehydration vehicles immediately after exercise.
7. The most effective option is an electrolyte drink combined with food, which provides the highest total intake of sodium together with adequate volume and energy.

2023 IOC Consensus on Hydration

1. Dehydration impairs performance in most events, and athletes should begin exercise well hydrated.
2. Fluid intake during exercise should limit any reduction in body mass to less than approximately 2 per cent.
3. Sodium intake is required when sweat losses are high, and is particularly important when exercise lasts longer than 2 hours.
4. Athletes should not consume so much fluid during exercise that body mass actually increases.
5. Recovery rehydration should provide both water and the salts that were lost in sweat.