Muscles can be classified in the following ways:
Muscle comprises 40-50% of a person's total body weight.
Note: Superficial muscle lies closer to the surface, can be seen when contracted and causes movement. Muscles that lie below the superficial muscles are called deep muscles.
Types of muscle contractions
When a muscle is stimulated, the fibres tighten. The muscle can either shorten (concentric), stay the same length (isometric) or lengthen (eccentric).
Antagonistic - eg biceps / triceps - opposing sets of muscles. Agonist - bicep (primary muscle), antagonist - tricep
Synergist - a muscle that steadies a movement. When making a fist, the finger muscles are the agonists and the wrist extensors are the synergists.
Fixator - a fixator holds the origin of the agonist stable. Eg, abducting arm - deltoid is abductor, fixators are other flexors keeping the scapula in position eg rhomboids.
Notes on above: