1. How Muscles Attach to Bone

2. Introduction Skeletal muscle attaches to bone one of two ways
Indirectly: the epimysium extends past the muscle as a tendon and then attaches to the periosteum of the bone
Epimysium: the sheath of connective tissue that surrounds the exterior of the muscle fibre
Directly: the epimysium adheres to and fuses with the periosteum
Periosteum: the outer membrane that covers the bone

3. Antagonistic Pairs Skeletal muscles are arranged as opposing pairs
While one muscles flexes, the other must extend to allow for the bone to move
The flexor and extendor are known as antagonistic muscles

4. Agonist vs. Antagonist
The muscle primarily responsible for movement of a body part is referred to as the agonist
The muscle that counteracts the agonist, extends or lengthens when the agonist contracts, is referred to as the antagonist
Example: in elbow flexion, the agonist is the biceps and the antagonist is the triceps

5. Origin and Insertion
When a skeletal muscle contracts, it causes movement of the bone it is attached to
The point where the muscle attaches to the more stationary of the bones of the axial skeleton is called the origin
The point where the muscle attaches to the bone that is moved most, is called the insertion

7. Types of Muscle Contraction
3 different types of muscle contractions
The term contraction does not necessarily mean that the muscle has shortened, but rather that tension has been generated
Concentric: occurs when muscle fibres shorten
- example: the biceps shorten when lifting an object
Eccentric: occurs when the muscle fibres lengthen
- the biceps lengthens as the same weight is placed back on the ground
3. Isometric: occurs when the muscle fibres do not change in length
- when you try to lift an immovable object

9. Muscle Contraction During Exercise
Isotonic Exercise
involves concentric contraction (shortening) and lengthening of the muscle
Example: weight training with dumbbells and barbells – as the weight is lifted, the muscle shortens
Other examples: chin-ups, push-ups, sit-ups

10. Isometric Exercise Muscle fibres maintain a constant length No motion
These exercises are usually performed against an immovable object
Example: pressing your arm into the wall
These exercises are frequently used in rehabilitation

11. Isokinetic Exercise
Involves using machines to control the speed of contractions
These machines allow for force to be exerted at a constant and pre-set speed
These types of machines are only used by high- performance training centres and professional teams
Not available to the public