Lecture on Biomechanics: Factors Affecting Human Strength and Power

Introduction

• Lecturer: Dr. Goodin
• Topic: Factors affecting human strength and power
• Reference: Chapter 2 of "Essentials of Strength Training and Conditioning" by NSCA, specifically by Dr. Jeffrey McBride

Key Definitions

Strength

• Defined as the capacity to exert force at any given speed.
• Strength is limited by speed due to contractile velocity components at the muscle fiber level.
• Example: Greater force exerted in a back squat compared to a vertical jump due to time limitations.

Acceleration

• Change in velocity per unit of time.
• Associated with resistive force by Newton’s second law: Force = Mass x Acceleration.

Power

• Loosely defined as explosive strength in athletics.
• Scientifically defined as the rate of doing work.
• Power = Force x Velocity.
• Example: Comparing the throw heights of a 6 lb vs. a 60 lb medicine ball.

Work

• Defined as the product of force exerted on an object and the distance it moves in the direction of the force.
• Work = Force x Displacement.
• Example: Differences in work between a tall and a short individual lifting the same weight.

Negative Work

• Work performed on the muscle during eccentric muscle actions.

Angular Displacement

• The angle through which an object rotates, measured in degrees.

Rotational Work

• Calculated as Torque x Angular Displacement.
• Torque: Rotational equivalent of force, tendency of an object to rotate.

Strength vs. Power

• Both reflect the ability to exert force at a given velocity.
• Examples:
  • Powerlifting: High levels of strength at slower speeds.
  • Olympic Weightlifting: High power through explosive movements.

Examples

• Powerlifting: Ray Williams squatting 183.5 kg, showcasing slow, powerful strength.
• Weightlifting: Clarence Kennedy performing a clean and jerk at 222.5 kg, demonstrating explosive power.
• Athletics: Werner Gunthor's plyometrics routine illustrating explosive strength.

Conclusion

• Strength and power are biomechanical terms that must be used appropriately.
• Strength involves exerting force with varying time constraints.
• Power involves exerting force quickly, demonstrated in explosive movements like weightlifting.

Upcoming Topics

• Next video will cover biomechanical determinants of strength and power in humans.

• Questions: Encouraged to ask questions in comments.
• Stay Tuned: For the next video on biomechanical determinants of strength to power.
• End Note: Stay strong!