Skeletal muscles are attached to bones by strong tissues called tendons. The muscle contracts when the nervous system sends a message to the muscle. This means it shortens and moves the bone or tissue it is attached to. This is what causes movement.
Every movement relies on one or more muscles pulling on a bone. Muscles never push on a bone. Movement is possible because muscles cross one or more joints. They are often grouped together by the similar nature of their actions, e.g. the abdominal muscles and the quadriceps muscle group.
Muscles make up around 40% of the body weight. Muscles develop strength with appropriate exercise, and they learn to work better together through practice. Co-ordination is the term used when muscles learn to work well together as a team to perform skills. Muscles need energy to contract. Exercise over a period of time requires oxygen and fuel, like sugar and fat. This means that the energy supplies in the muscle can support short bursts of physical activity. However, a prolonged, sustained effort will tire the muscle eventually. This is called muscle fatigue.
Muscles of the upper limb:
- Muscles that attach the shoulder girdle to the axial skeleton: trapezius, levator scapulae, serratus anterior, pectoralis minor
- Muscles that attach the humerus to the axial skeleton:
pectoralis major, latissimus dorsi
- Muscles that attach the humerus to the shoulder girdle: teres major, rotator cuff muscles (Supraspinatus, Infraspinatus, Teres Minor, Subscapularis), deltoid.
- Muscles of the shoulder: Deltoid, Infraspinatus, Subscapularis, Teres minor, Supraspinatus, Teres major
- Muscles of the arm: anterior (biceps brachii, brachialis) posterior (triceps)
- Muscles of the forearm: mainly extensors and flexors
- Muscles of the hand: extrinsic and intrinsic muscles
Muscles of the lower limb
- Muscles that rotate and abduct the thigh: gluteal muscles and hip flexors (lateral rotation).
- Muscles that adduct the thigh: adductor muscles(Adductor longus, brevis,gracilis.etc)
- Muscle that extends the thigh: hamstring group.
Recap- Movements of Bones
- Flexion : Forward bending
- Extension : Backward bending
- Lateral bending : Side to side bending
- Rotation : Twisting of the vertebrae relative to each other
There are three planes of motion in which we move. They are:
The Sagittal plane passes through the body front to back, so dividing it into left and right. Movements in this plane are the up and down movements of flexion and extension
The frontal plane divides the body into front and back. Movements in this plane are sideways movements, called abduction and adduction
This plane divides the body into top and bottom. Movements in this plane are rotational in nature, such as internal and external rotation, pronation and supination.