Lecture Notes: Isotonic vs. Isometric Contraction

Introduction to Muscle Contraction

• Isotonic Contraction

  • Involves movement of muscles
  • Two types: concentric and eccentric

• Isometric Contraction

  • Muscle contracts without changing joint angle
  • Common in activities like yoga

Isotonic Contraction Details

• Concentric Contraction

  • Muscle fibers shorten during contraction
  • Example: Bicep curls
  • Biceps Brachii Example
    • Origin: Supraglenoid tubercle and coracoid process
    • Insertion: Radial tuberosity on the radius
    • Action: Flexion of the elbow
    • Muscle bunches up as it contracts

• Eccentric Contraction

  • Muscle fibers lengthen while still contracting
  • Occurs when the muscle is lengthening under tension

Isometric Contraction

• Muscle is engaged without changing joint angle
• Example: Holding a cup of water and filling it
• Muscle still works even if the joint angle doesn’t change
• Common in yoga where poses are held for extended periods
• More workload applied over time without joint angle change

Summary

• Isotonic: Includes dynamic muscle movements (concentric and eccentric).
• Isometric: Muscle tension without joint movement.
• Both types involve muscle work but differ in how the muscle length changes or doesn’t change.

Use these notes to understand how different types of muscle contractions function and how they apply in various physical activities.