kinesiology chapter 2

Introduction to Muscle Movement Terminology

• Understanding movement involves recognizing the roles of different muscles based on their actions.
• Terms:
  • Agonist: The prime mover in a specific movement.
  • Antagonist: Muscle that performs the opposite action of the agonist.
  • Synergist: Assists the agonist in performing its action.
  • Stabilizer: Prevents unwanted movement during muscle contractions.

Definitions and Concepts

Agonist and Antagonist

• Movement examples:
  • Flexion (e.g., elbow flexion).
  • Biceps (agonist for elbow flexion), responsible for
  • Flexion of the elbow.
  • Flexion of the shoulder.
  • Triceps (antagonist for elbow flexion), responsible for
  • Extension of the elbow.
  • Extension of the shoulder.

Synergist

• Assists the agonist in its function.
• Example:
  • The quadriceps group primarily facilitates knee extension, while the rectus femoris also assists with hip flexion, making it a synergist in the knee extension context.

Stabilizers

• The role of stabilizers is to ensure stabilization of the proximal segment during movement.
• Example:
  • During elbow flexion, stabilizer muscles like the deltoid ensure stability at the shoulder to allow effective bicep contraction.

Functional Examples in Sport

Kicking a Soccer Ball

• Agonist:
  • Iliopsoas - hip flexor.
• Antagonist:
  • Muscles responsible for hip extension, primarily the gluteus maximus.
• Synergist:
  • Rectus femoris assists in both hip flexion and knee extension.
• Stabilizer:
  • Gluteus medius aids in stabilizing the pelvis during the kick.

Reciprocal Inhibition

• This concept involves the nervous system's facilitation to inhibit antagonists during an agonist action.
• Example:
  • During elbow flexion with a heavy load, the triceps are inhibited by the nervous system to prevent conflict between the agonist and antagonist actions.

Muscle Length and Contraction Types

Concentric and Eccentric Contractions

• Concentric: Muscle shortens as it contracts to create movement.
• Eccentric: Muscle lengthens under tension.
• Optimal Length:
  • Muscles have an optimal length for generating force, referred to as resting length, positioned between maximum contraction and maximum lengthening.
• Advantages of Optimal Length: Increases effectiveness of actin-myosin interaction, facilitating better contraction mechanics.

Active and Passive Movements

Active Movements

• Require muscle contraction and are driven by neural activation.
• Example of active movement includes voluntarily lifting an arm.

Passive Movements

• Movements occur without neural activation, often facilitated by an external force.
• Common in rehabilitative contexts where active movement is contra-indicated (e.g., post-surgical recovery).

Active and Passive Insufficiency

Active Insufficiency

• Occurs in biarticular or multiarticular muscles when they are shortened beyond capability to generate tension.
• Example: Trying to flex a fist while fully flexing the wrist results in ineffective finger flexion.

Passive Insufficiency

• Arises when an opposing muscle (often biarticular) cannot stretch adequately to permit movement due to being overly lengthened.
• Example: Lifting a leg while fully flexing the knee illustrates how tight hamstrings may limit hip movement.

Importance of Lines of Pull

• Muscle actions are dictated by their lines of pull between their origin and insertion.
• Example:
  • The bicep brachii pulls towards its origin at the scapula, crossing the shoulder and elbow joints, thus facilitating elbow flexion and shoulder actions due to its biarticular nature.

Conclusion

• Understanding these terms and concepts is critical in kinesiology for evaluating muscle function and movement.
• Application of knowledge applies to therapy, strength training, and biomechanics.

Discussion and Group Work

• Students will be organized into groups to consolidate understanding and connect topics of chapters one and two for comprehensive learning.