Hydration and Thermal Stress (1)

Hydration and Thermoregulation

• Importance of hydration for fitness

• Core concepts of thermoregulation

Elements in the Human Body

• Six major elements critical to human health:

  1. Oxygen

  2. Carbon

  3. Hydrogen

  4. Nitrogen

  5. Calcium

  6. Phosphorus

Importance of Water in the Body

• Acts as a solvent for molecules and ions

• Vital for regulating body temperature

Amount of Water in Various Body Parts

• Brain: 73%

• Heart: 73%

• Lungs: 83%

• Kidneys: 79%

• Muscles: 79%

• Skin: 64%

• Bones: 31%

• At various life stages:

  • At Birth: ~78%

  • 1 Year: ~60%

  • Adult Women: 55%

  • Adult Men: 65%

Hydrating Foods

• Hydration can also be achieved through foods rich in water:

  • Watermelon: 93% water

  • Salad greens: 90% water

  • Berries: 90% water

  • Tomatoes: 95% water

  • Radishes, Cauliflower, Zucchini, Peppers: ~90% water

  • Acorn and Butternut squash: 85% water

Mechanism for Keeping Hydrated

• Water absorption process:

  • Ingested water passes through the stomach and absorbed by the intestines

  • Transported into blood vessels for distribution

• Importance of hydration:

  • Required for normal physiological functions

  • Essential for performance and daily activities

Metabolism and Water

• Overview of aerobic metabolism:

  • Glycolysis, Citric Acid Cycle, Oxidative Phosphorylation

    • Converts glucose into energy while producing water and carbon dioxide

    • Overall reaction: C6H12O6 + O2 -> 6 CO2 + 6 H2O + ATP

Dehydration Synthesis and Hydrolysis

• Dehydration Synthesis:

  • Combines organic molecules, releasing a water molecule, requiring energy

• Hydrolysis:

  • Breaks down organic molecules, using a water molecule and releasing energy

Understanding Dehydration

• Signs indicating dehydration levels:

  • Mild to moderate: thirst, dry mouth, fatigue, headaches

  • Severe: rapid breathing, rapid heartbeat, dizziness, unconsciousness

Impact of Dehydration on Performance

• Effects of hypohydration:

  • Declines in exercise performance, cognitive functions, and mood

  • Increased risk for cardiovascular disease with chronic dehydration

  • Performance is detrimentally affected by as little as 0.5% body weight loss

Checking Hydration Status

• Coloration scale: 1-3: Hydrated; 4-5: Mild dehydration; 6-8: Severe dehydration

• Recommendations for rehydrating:

  • Use oral rehydration solutions for severe dehydration

  • Water is typically sufficient for mild dehydration

Treating Dehydration

• For mild dehydration: increase water intake

• Severe dehydration:

  • Special rehydration solutions with electrolytes recommended

  • Fluid replacement via IV may be necessary in critical cases

Oral Rehydration Therapy (ORT)

• Mechanism:

  • Sugar improves absorption of electrolytes in the intestines

  • Salt enhances water absorption into intestinal walls

Recommendations for Water Intake

• Daily fluid requirement by body weight:

  • Calculate based on body weight (lbs) x 2 = fluid oz. per day

• Dietary Reference Intakes for different age groups:

  • 1-3 years: 1.3 liters

  • 4-8 years: 1.7 liters

  • 14-18 years: 3.3 liters (males), 2.3 liters (females)

  • Adults: 3.7 liters (males), 2.7 liters (females)

Hydration During Exercise

• Guidelines for hydration around exercise:

  • Drink 16-24 oz before run, 8 oz 30 minutes before, 4 oz every 15 minutes during, and at least 16 oz for every pound lost post-exercise

Thermoregulation

• Body maintains temperature between 36.5–37.5 °C (97.7-99.5 °F)

• Balance between heat gain and heat loss is crucial

Mechanisms of Heat Exchange

• Heat exchange through:

  • Conduction, Convection, Radiation, Evaporation

  • Each plays a role in body temperature regulation and homeostasis

Effects of Sweat and Sweat Rates

• Factors influencing sweat rates:

  • Increase: high temperature/humidity, exercise intensity, larger body size

  • Decrease: cooler temperatures, lower intensity, better acclimatization

Impact of Dehydration on Performance

• Graphs showing relationship between dehydration percentage and performance levels

• Awareness of hydration status is critical for maintaining exercise performance

Final Key Points

• Water is vital for the body, especially during exercise

• Hydration strategies are essential, especially in high temperatures or prolonged activity

• Sports drinks should be used when appropriate but water is generally recommended first

• Plan hydration before, during and after physical activities to maintain peak performance.