Muscle

1. Muscle

2. What are muscles? • Machines • purpose of machines is to help us do work.

3. Characteristics of Muscle Tissue • Extensibility • Elasticity • Contractility • Irritability • Amplitude • Viscosity

4. What is a muscle contraction?

5. Types of Contractions • Concentric Contraction • Static Contraction • Eccentric Contraction • Isometric and Isotonic Contractions

6. Concentric Contractions • development of tension within a muscle with consequent shortening of the muscle. • the movement is caused by the muscle.

7. Static Contraction • development of tension within a muscle with no change in the overall muscle length. • goal is usually to maintain a position.

8. Eccentric Contraction • development of tension within a muscle resulting in lengthening of the muscle. • movement is caused by another force • contracting muscle tries to control the movement.

9. Mechanical Factorsdetermining specific movements • structure of the joint or joints muscle crosses • the orientation of the muscle’s line of pull to the axis or axes around which movement is permitted

10. Line of Pull • the direct line between the centers of the muscle’s attachments • one origin, one insertion • one origin, multiple insertions

11. Mechanical Axis • the straight line drawn connecting the centers of the joints at each end of the specific bone, or • from the center of the joint where the movement is occurring to the center of the distal end of the limb, if the limb is moving as a unit

12. Axis of Rotation • the angle formed by the line of pull and the mechanical axis.

13. Muscle Roles • Individual muscles take on a variety of roles at different times and under different circumstances. • there are six roles a muscle can assume

14. Muscles and their Roles • Muscles are not selective when stimulated to contract. • Resulting actions are partially determined by functions performed by other muscles attendant to the agonist.

15. Muscle Roles • Agonist • Antagonist • Fixator • Regulator • Neutralizer • Synergist

16. Agonist • Prime Mover • causes a concentric contraction

17. Antagonist • refers to a muscle whose function is opposite to that of some muscle tending to cause a movement. • Three different functions: • relax throughout the movement • relax initially, but contract toward the end of the movement to prevent injury • contract throughout the movement

18. Fixator • any muscle that contracts to anchor or steady the position of a particular bone • Two categories of fixators: • Stabilizing role - • Supporting role -

19. Regulator • used to identify a muscle contracting eccentrically to control a movement caused by an external force.

20. Neutralizer • acts to prevent the undesired action of another contracting muscle without interfering with the desired function of that other muscle • two types • mutual neutralizer - • true neutralizer -

21. Synergist • usually assigned to the synchronous action of two joint muscles • 2 types • Concurrent pattern - • Countercurrent pattern -

22. Control of Movement • Coordination is an orchestrated sequencing of binary impulses • Reciprocal Innervation (Sherrington’s Principle) • inhibition of one member of antagonistic pair • Corollary • inhibition of muscle is inhibited

23. Conditions for Co-contraction • when an exact amount of tension or accurate placement of a limb is needed • deceleration of limb • to stabilize the wrist for precise hand movements or for a powerful grip

24. Ballistic Movements • Three phases: • Acceleration- • Inertial- • Deceleration-

25. Ballistic Movements • muscle initially contracts to move the limb, but then the limb is carried through space due to momentum • antagonistic muscles fire to slow down the speeding limb

26. Stretch Reflex • occurs in skilled ballistic movements • muscle is stretched quickly, resulting in a stronger contraction

27. Olson’s Principles • Dealt with free weights only and considered: • direction of movement relative to the line of gravity • the type of contraction • the muscle group used

28. Olson’s 1st Principle • If the movement is against the line of gravity: • the muscle causes the movement • the contraction is concentric • the muscle group that should perform the action, performs the action

29. Olson’s 2nd Principle • If the movement is through the line of gravity: • the muscle causes the movement • the contraction is concentric • the muscle group that should perform the action, performs the action

30. Olson’s 3rd Principle • If the movementis toward the line of gravity: • the resistancecauses the movement • the contraction is eccentric • the muscle group that is opposite to the joint movement acts to control the movement

31. Ulibarri’s Corollaries toOlson’s Principles • These corollaries restate Olson’s Principles relative to the: • direction of the weight (resistive force) • type of muscle contraction • muscle group used

32. Ulibarri’s 1st Corollary • If the weight (resistive force) moves against the line of gravity: • the muscular force causes the movement • the contraction is concentric • the muscle group that should do the action, performs the action

33. Ulibarri’s 2nd Corollary • If the weight (resistive force) moves toward the line of gravity: • the resistive force causes the movement • the contraction is eccentric • the muscle group that is opposite to the joint action acts to control the movement