Lecture Notes: Torque and Moments

Recap of Last Class

• Discussed torque and how to calculate it.
• Practical and anatomical examples of torques.
• Internal joint moment.
• Muscle force component and co-contraction.

Today's Lecture

• External Moments
  • Manipulating moment arm length.
  • Practical examples of joint moments.
  • Calculating joint moments in static equilibrium.
  • Potential discussion on stability and equilibrium.

Co-Contraction

• Positive Effects:
  • Fine motor control (e.g., surgery, writing).
  • ACL and hamstring examples.
• Negative Effects:
  • Exercise examples (e.g., bicep curl with too much tricep activation).
  • Compressive forces on cartilage.

External Joint Moments

• Created by:
  • Segment mass and weight.
  • External objects (e.g., dumbbells).
  • Ground reaction forces.
• Important for exam: Three contributors to external moments.

Practical Example: Elbow Flexion

• Static Equilibrium: Relaxing the bicep leads to elbow extension because of external extension moment.
• For static equilibrium, internal flexor moment combats external extension moment.

Manipulating External Demand

• Torque Equation: Torque = Force x Distance
• Exercise Difficulty
  • Increase: Heavier dumbbells or longer moment arm.
  • Decrease: Shorter moment arm.

Examples of Manipulating Moment Arms

• Push-ups and Inclines: Shortening the moment arm makes exercises easier.
• Carrying Groceries: Keep bags close to body to reduce torque.

Ground Reaction Forces

• Influence joint loading.
• Example of Abby Steiner: Analyzing ground reaction force vectors.
• Joint Moments:
  • External knee flexion moment.
  • Internal knee extension moment needed.
  • Hip and knee joint torque considerations.

Joint Moments in the Frontal Plane

• External Knee Adduction Moment:
  • Associated with ACL tears and osteoarthritis.
  • Important for exam.

Calculating Joint Moments

• Example Problems:
  • Calculating torque at a joint.
  • Using rotary components and lever arms for calculations.

Static Equilibrium

• Midpoint of Bicep Curl:
  • Force of bicep required to maintain balance.
  • Considerations of weight and positioning.

Complex Calculations

• Lever arm vs moment arm.
• Importance of angle of pull in calculations.
• Practical application in exercises like squats and deadlifts.

Closing

• Exam hints: Consideration of angle of pull.
• Wrap-up questions for review.
• Encouragement to practice problem-solving on static equilibrium and joint moments.