Lecture Notes

Lecture 1: Bioenergetics

What is ATP?

• ATP (Adenosine triphosphate): Composed of adenine, ribose, and three linked phosphates.

• Synthesis: ADP + Pi → ATP

• Breakdown: ATP → ADP + Pi + Energy (via ATPase)

• Usage Rate: Each human cell uses ~10 million ATP/second (~1-2 billion/minute).

Importance of ATP

• Gibbs Free Energy (∆G): ∆G = total free energy of products – total free energy of reactants.

• Macromolecules for ATP Production: Primarily carbohydrates, alongside fats and proteins.

Pathways for ATP Production

1. Anaerobic Glycolytic ATP Production

• Efficiency: 1 glucose → 2 ATP (6-7%).

• NAD Recycling: Important in Anaerobic Glycolysis.

• Lactic Acid Processing: Key concept to understand.

2. Aerobic Catabolic ATP Production

• Efficiency: 1 glucose → 30-33 ATP (34%).

• High Energy Phosphagens: Utilized without glucose/O2 for muscle contraction; excess ATP stored at rest.

3. Lactate as a Fuel Source

• Cori Cycle: Lactate Shuffle for energy production.

• Enzymatic Role: Facilitate oxidation-reduction reactions.

Metabolic Rate

• Definition: Total cellular reactions of synthesis and breakdown.

• Electron Transport Chain: Oxygen is essential for aerobic energy production.

• Efficiency Metrics: 34% efficiency per CH2O (4.2 kcal/g) or fat (9.4 kcal/g).

  • Potential Energy: 1 mole of glucose = 686 kcal/mole → yields 32 moles of ATP (7.3 kcal each).

Lecture 2: Muscle and Nervous System

Muscle Fiber Types

• Classification: Biochemical, anatomical, and physiological differences.

• Mitochondria and Fiber Size: Vary between Slow Oxidative (SO), Fast Glycolytic (FG), and Fast Oxidative Glycolytic (FOG) fibers.

Variability and Adaptation of Muscle Fibers

• Genetic Determination: All muscles have genes for each type of myosin.

• Fiber Type Changes: Possible through resistance and endurance training, but duration and difficulty vary.

  • Resistance training leads to Type I (SO) to Type II (FG) switch in ~2 months.

  • Endurance training leads to Type II (FG) to Type I (SO) switch in 2-6 months.

Motor Units and Recruitment

• Motor Units: Composed of various independent fibers. Recruitment goes from Slow Twitch to Fast Twitch based on movement demand.

• Neural Activation: Not all motor units are activated simultaneously; differential activation plays a role in movement control.

Lecture 3: Fuel Nutrition

Heat and Exercise

• Body Heat Production: Related to exercise intensity and physiological responses.

• Precooling Impact: Can optimize endurance performance; mechanisms of cooling methods (e.g., slushies vs. cold compresses).

• Heat Stroke Susceptibility: Three factors influencing individual responses.

Hydration and Thirst

• Changing Hydration Guidelines: Evolution of recommendations affecting performance.

• Thirst vs. Dehydration: Investigating performance implications.

Carbohydrate and Performance

• Glycogen Influence: Duration of exercise affects reliance on muscle glycogen; ingesting carbohydrates can delay fatigue.

• Energy Drinks: Role in improving performance via glucose and fructose mix.

Lecture 4: Fatigue and Factors Affecting Performance

Types of Fatigue

• Central vs. Peripheral Fatigue: CNS accounts for 10-15%, while peripheral factors mainly contribute to fatigue.

• Mechanical Factors: Include sarcomere structural arrangements, Ca²+ availability, and ATP's role.

Fatigue Experiments

• Experimental Models: Understand trade-offs in methodologies (e.g., in vivo, isolated muscle).

Inducers of Peripheral Fatigue

• High [H+]: Can reduce force and maximal shortening velocity.

• Free Radicals: Affect actin and myosin efficiency, impacting overall fatigue.

• ATP Energetics: ATP levels remain relatively stable during exercise, with specific reactions stimulating glycolysis.

Summary of Performance Factors

• Tailoring Factors: Variation in performance for different exercise types and durations.

• Central vs. Peripheral Fatigue: Ongoing research exploring their respective impacts.

• Overtraining Symptoms: Can significantly affect performance, mood, appetite, and exertion level.