Sports, Exercise and Health Science | Hydration and nutrition

Welcome to Hydration and Nutrition! (A.2)

Hello future SEHS expert! This chapter, Hydration and Nutrition, is absolutely critical. Why? Because the food we eat and the liquids we drink directly determine how efficiently our body performs, recovers, and even adapts to training.
Think of the human body as a high-performance race car. Nutrition is the fuel and oil, and hydration is the coolant. Get this wrong, and performance crashes!
We will break down water balance, the role of fuel sources (macros), the importance of tiny helpers (micros), and specific strategies to maximize athletic output.

Part 1: The Foundation - Water and Electrolyte Balance

A. Water: The Most Important Nutrient

Water makes up about 60% of the body mass in an adult and is essential for virtually every physiological process.

Key Roles of Water in the Body:

• Transportation: Water is the main component of blood plasma, transporting nutrients, oxygen, and hormones to cells, and removing waste products (like CO\(_2\) and urea).
• Temperature Regulation: This is crucial! When we exercise, water absorbs heat and is evaporated from the skin (sweating), cooling the body down.
• Lubrication: Water helps lubricate joints and mucous membranes (like the eyes and digestive tract).
• Cell Structure: It maintains the shape and integrity of cells.

Analogy: If your body is a city, water is the entire road network, the public transit system, and the air conditioning all rolled into one!

B. Dehydration and its Effects

Dehydration occurs when the loss of body fluids (mostly water and electrolytes) exceeds the intake. Even a 2% loss of body mass due to fluid deficit can significantly impair performance.

Step-by-Step Effects of Dehydration on Performance:

1. Reduced Plasma Volume: Less water means less liquid component in the blood.
2. Increased Blood Viscosity: The blood becomes thicker, making it harder for the heart to pump.
3. Increased Core Temperature: Less fluid is available for sweating, causing the body's internal temperature to rise (hyperthermia).
4. Cardiovascular Strain: The heart rate increases (trying to pump thick blood faster), leading to earlier fatigue.
5. Impaired Cognitive Function: Decision-making and concentration decrease.

Key Term: Electrolytes are minerals (like sodium, potassium, and chloride) that carry an electrical charge when dissolved in water. They are essential for nerve and muscle function, and maintaining proper fluid balance. We lose them in sweat, which is why sports drinks often contain them.

Part 2: The Energy Providers - Macronutrients

Macronutrients are nutrients needed in large amounts. They provide the body with energy, measured in kilojoules (kJ) or kilocalories (kcal). The three main macros are Carbohydrates, Fats, and Proteins.

A. Carbohydrates (CHO)

Carbohydrates are the body’s preferred and most readily available source of energy, especially for high-intensity exercise.

Structure and Function:

• Structure: Made up of carbon, hydrogen, and oxygen atoms (C\(_n\)H\(_{2n}\)O\(_n\)). The basic unit is a simple sugar (monosaccharide).
• Energy Yield: Approximately \(17 \text{ kJ/g}\).
• Storage: Stored in the liver and muscles as Glycogen.

Simple vs. Complex Carbs:

• Simple (Sugars): Broken down quickly (e.g., glucose, fruit). Provide a fast energy boost.
• Complex (Starches/Fibre): Broken down slowly (e.g., whole grains, vegetables). Provide sustained energy.

Memory Aid: C.H.O. = Carbon, Hydrogen, Oxygen. Carbs are our fast cash fuel.

B. Fats (Lipids)

Fats are crucial for long-duration, low-intensity activities. They provide the largest reserve of potential energy.

Structure and Function:

• Structure: Primarily made of triglycerides (glycerol and three fatty acids).
• Energy Yield: Approximately \(37 \text{ kJ/g}\). (More than double that of carbs!)
• Roles: Energy storage, insulation, protection of vital organs, and transport of fat-soluble vitamins (A, D, E, K).

Did you know? Even the leanest athletes have enough stored fat to fuel many hours of activity. The challenge is accessing this fuel quickly during high-intensity work!

C. Protein

Protein is the building block of the body, essential for growth, repair, and immune function. It is generally the last resort for energy.

Structure and Function:

• Structure: Made up of chains of amino acids. Some amino acids are "essential" (must be obtained through diet).
• Energy Yield: Approximately \(17 \text{ kJ/g}\).
• Roles: Building and repairing muscle tissue, making enzymes and hormones.

Common Misconception: Athletes need huge amounts of protein. While protein needs are higher, excessive intake is unnecessary and can strain the kidneys. Focus on adequate intake for repair, not huge amounts for energy.

Part 3: The Supporting Cast - Micronutrients

Micronutrients are nutrients needed in small quantities. They do not provide energy, but they are vital catalysts that help release the energy stored in macronutrients, regulate processes, and protect cells.

A. Vitamins

Organic compounds necessary for metabolic functions.

• Water-Soluble Vitamins (B and C): Cannot be stored by the body, so they must be consumed regularly. They often function as co-enzymes (helpers) in energy release.
• Fat-Soluble Vitamins (A, D, E, K): Stored in the body's fat tissues. Excessive intake can be toxic (hypervitaminosis). Vitamin D is especially important for calcium absorption and bone health.

B. Minerals

Inorganic elements necessary for structural development (bones, teeth) and regulatory functions (fluid balance, nerve transmission).

• Calcium: Essential for bone structure and muscle contraction.
• Iron: Crucial component of Haemoglobin, which transports oxygen in the blood. Iron deficiency (anaemia) severely reduces aerobic performance.
• Sodium/Potassium: Key electrolytes involved in fluid balance and nerve impulse conduction.

Tip for Struggling Students: Remember that "Micro" means small. Micronutrients are the tiny helpers that keep the engine running smoothly—they don't supply the fuel, they just make sure the fuel combusts properly!

Part 4: Fueling Performance - Nutritional Strategies

An athlete’s dietary needs change dramatically depending on the timing of exercise. Nutritional planning aims to maximize glycogen stores and promote rapid recovery.

A. Pre-Exercise Nutrition (The Build-Up)

The primary goal is to maximize muscle and liver glycogen stores without causing gastrointestinal distress.

• 2-4 hours before: Consume a meal high in complex (low GI) carbohydrates, moderate in protein, and low in fat and fibre (as fat and fibre slow digestion).
  Example: Oatmeal, toast, or pasta.
• Glycaemic Index (GI): This scale ranks foods based on how quickly they raise blood glucose levels. Low GI foods are preferred pre-exercise for sustained energy.

Carbohydrate Loading: This is a specific strategy used for endurance events (90+ minutes) to super-saturate muscle glycogen stores, increasing the body's fuel reserve capacity.

B. Nutrition During Exercise (The Top-Up)

For exercise lasting longer than 60 minutes, the goal is to spare glycogen and maintain blood glucose levels.

• Fuel: Consume simple carbohydrates (high GI) quickly absorbed into the bloodstream. Sports gels or drinks are common.
• Hydration: Focus on fluid intake (with electrolytes) to replace sweat loss.
• Rate: Athletes typically aim for 30–60g of carbohydrates per hour of intense exercise.

C. Post-Exercise Nutrition (The Recovery)

The goal is immediate refuelling and repair. This is known as the "Glycogen Window"—a 1–2 hour period where muscles are highly receptive to absorbing nutrients.

• Refuel (Carbs): Consume high GI carbohydrates to rapidly replenish muscle glycogen stores.
• Repair (Protein): Consume protein (amino acids) to initiate muscle tissue repair and synthesis.
• Ratio: A common recommendation is a 3:1 or 4:1 ratio of Carbohydrate to Protein.
  Example: Chocolate milk or a high-carb smoothie with protein powder.

Part 5: Ergogenic Aids (HL Extension Focus, but Relevant to All)

An ergogenic aid is any substance or phenomenon that enhances performance or speeds up recovery. We focus only on legal and commonly researched nutritional aids.

A. Creatine

• What it is: A compound found naturally in muscle cells, primarily used to recycle ATP in the ATP-PC system (used for short, maximal bursts of energy).
• Mechanism: Supplementation increases the stores of Phosphocreatine (PCr) in the muscles. More PCr means the athlete can maintain maximal effort for a few seconds longer or recover faster between sets.
• Performance Benefit: Improved power and strength in high-intensity, short-duration activities (e.g., sprinting, weightlifting).

B. Caffeine

• What it is: A central nervous system (CNS) stimulant.
• Mechanism:
  1. It reduces the perception of effort (makes the exercise feel easier).
  2. It potentially increases the mobilization and use of fat (FFA) as a fuel source, sparing glycogen stores during endurance exercise.
• Performance Benefit: Enhanced endurance and reduced fatigue perception across various activities.

C. Sodium Bicarbonate (Bicarbonate Loading/Buffering)

• What it is: A common household baking ingredient (baking soda) used as an internal buffer.
• Mechanism: During intense anaerobic exercise (like a 400m sprint), the body produces Lactic Acid, which quickly dissociates into Lactate and hydrogen ions (\(H^+\)). The accumulation of \(H^+\) causes the "burning" sensation and fatigue. Bicarbonate acts as a buffer, neutralizing these ions and slowing down muscle fatigue.
• Performance Benefit: Enhanced performance in activities lasting 1–7 minutes (high-intensity, anaerobic activities).