1. Issues that Affect Performance Course
Section 2 Learning Activity
The following definitions are taken from the book “Equine Lameness for the Layman” by Dr. Robert Grisel and are a review of terms associated with function of the muscular and nervous systems.

2. Concentric Muscle Action
Issues that Affect Performance Course
Section 2 Learning Activity - Definitions
Concentric Muscle Action

3. Concentric Muscle Action
Issues that Affect Performance Course
Section 2 Learning Activity - Definitions
Concentric Muscle Action
Contraction or shortening of muscle fibers.

4. Eccentric Muscle Action
Issues that Affect Performance Course
Section 2 Learning Activity - Definitions
Eccentric Muscle Action

5. Eccentric Muscle Action
Issues that Affect Performance Course
Section 2 Learning Activity - Definitions
Eccentric Muscle Action
Relaxation or lengthening of muscle fibers.

6. Myopathy Issues that Affect Performance Course
Section 2 Learning Activity - Definitions
Myopathy

7. Myopathy Issues that Affect Performance Course
Section 2 Learning Activity - Definitions
Myopathy
Muscle disease

8. Neuropathy Issues that Affect Performance Course
Section 2 Learning Activity - Definitions
Neuropathy

9. Neuropathy Issues that Affect Performance Course
Section 2 Learning Activity - Definitions
Neuropathy
A disease or condition affecting the nervous system.

10. Fibrotic Myopathy Issues that Affect Performance Course
Section 2 Learning Activity - Definitions
Fibrotic Myopathy

11. Fibrotic Myopathy Issues that Affect Performance Course
Section 2 Learning Activity - Definitions
Fibrotic Myopathy
Pathologic condition characterized by the presence of scar tissue within one or more muscle bellies.

12. Issues that Affect Performance Course
Section 2 Learning Activity –
Biomechanical Lameness
Following are some conditions that might be observed in the horse that are described as biomechanical lameness, that is, there is something limiting within the physical structure of the horse.
These may or may not be associated with pain and are just one of the useful classifications in trying to understand the various types of lameness.

13. Issues that Affect Performance Course
Section 2 Learning Activity –
Biomechanical Lameness
Observed Effect: The muscle cannot contract to its minimum length.
Potential Underlying Issue:
Myopathy resulting in decreased myofiber contractility.
Corresponding joint has limited range of motion.

14. Issues that Affect Performance Course
Section 2 Learning Activity –
Biomechanical Lameness
Observed Effect: The muscle contracts beyond its normal minimum length.
Potential Underlying Issue:
Corresponding (displaced) bone fracture with loss of architectural integrity, allowing the attachment points to move too close together.
Corresponding joint dislocation or loss of collateral support, allowing the attachment points to move too close together.

15. Issues that Affect Performance Course
Section 2 Learning Activity –
Biomechanical Lameness
Observed Effect: The muscle contracts too slow.
Potential Underlying Issue:
Myopathy resulting in muscle atrophy/weakness.
Neuropathy resulting in muscle paresis (slight or partial paralysis).

16. Issues that Affect Performance Course
Section 2 Learning Activity –
Biomechanical Lameness
Observed Effect: The muscle contracts too fast.
Potential Underlying Issue:
Neuropathy resulting in hyperactive muscle function.

17. Issues that Affect Performance Course
Section 2 Learning Activity –
Biomechanical Lameness
Observed Effect: The muscle cannot contract at all.
Potential Underlying Issue:
Ruptured or detached muscle structure.
Neuropathy resulting in muscle paralysis.

18. Issues that Affect Performance Course
Section 2 Learning Activity –
Biomechanical Lameness
Observed Effect: The muscle cannot stretch to its maximum length.
Potential Underlying Issue:
Myopathy resulting in decreased myofiber elasticity.
Corresponding joint has limited range of motion.

19. Issues that Affect Performance Course
Section 2 Learning Activity –
Biomechanical Lameness
Observed Effect: The muscle stretches beyond its normal (maximum) length.
Potential Underlying Issue:
Corresponding displaced bone fracture with loss of architectural integrity, allowing the attachment points to move far apart from one another.

20. Issues that Affect Performance Course
Section 2 Learning Activity –
Biomechanical Lameness
Observed Effect: The muscle relaxes too slow.
Potential Underlying Issue:
Myopathy resulting in decreased myofiber elasticity.

21. Issues that Affect Performance Course
Section 2 Learning Activity –
Biomechanical Lameness
Observed Effect: The muscle relaxes too fast.
Potential Underlying Issue:
Myopathy resulting in decreased myofiber tone.

22. Issues that Affect Performance Course
Section 2 Learning Activity –
Biomechanical Lameness
Observed Effect: The muscle cannot relax at all.
Potential Underlying Issue:
Neuropathy resulting in hyperactive muscle function
Myopathy resulting in restrictive tissue fibrosis.