How Muscles Attach to Bone

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

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

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

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

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

1. Concentric: occurs when muscle fibres shorten- example: the biceps shorten when lifting an object

2. 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

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

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

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