Muscles and Movement
Muscles and Movement
Muscles can only contract and pull. Therefore, joints have to have two or more muscles working opposite each other.
As the first muscle contracts, so the second muscle relaxes. As the second muscle contracts, so the first muscle relaxes. This is known as antagonistic muscle action.
For this to occur one end of the muscle must be fixed, this is known as the origin. When the muscle contracts, the other end of the muscle then moves towards the origin.
The end that moves is known as the insertion.
A good example of this is the upper arm where the triceps and biceps areon opposite sides of the humerus.
The origins of both the triceps and the biceps are at the top of the humerus near the shoulder joint.
As the bicep contracts, the lower arm (radius and ulna) moves up towards the shoulder. The triceps relax to allow this movement to happen.
The bicep is the prime mover or agonist, while the tricep is the secondary mover or antagonist.
Muscles are attached to bones at either side of the joints by tendons.
These are very strong flexible cords of connective tissue that extend from the epimysium and transmit large amounts of energy from the muscle to the bone.
The ends of tendons are embedded into the surface of the bone.
There are three types of muscle contraction:
Isometric - During isometric contraction, the muscle remains the same length. While performing a handstand, many of the bodies muscles are contracting.
Isokinetic - Isokinetic contraction occurs when the speed of the contraction remains constant throughout the movement. An example of this can be seen in cycling.The legs are moving at a relatively constant speed, although forces applied by the leg alter during a peddling cycle.
Isotonic - Isotonic contraction can be divided into two types:
- Concentric: the muscle shortens as it contracts.
- Eccentric: the muscle lengthens but is still under tension.
Due to the range of movements required in sport, it is useful to be able to describe them technically:
Flexion: bringing two parts of a limb together - bending at the joint.
Extension: moving two parts of a limb away from each other - straightening at the joint.
Abduction: moving limbs away from the centre of the body.
Adduction: Moving limbs towards the centre of the body.
Circumduction: the movement of a limb around a joint.