The majority of the motions are of the rotary type and occur around an axis or fulcrum. These motions follow the physics of lever systems.
The various forces produced by contracting muscles have specific direction and magnitude.
Simple Pulley Systems
Another common mechanism of the human body is the simple pulley system. Here, the direction of force can be at an angle to the muscle.
During locomotion, the body uses several pendulums in the swinging of the upper and lower limbs.
Bones act as levers and as attachment sites for skeletal muscles.
The joint is the center, fulcrum, point, or axis of motion.
Skeletal muscles apply the forces for motion. Any given motion utilizes a group of muscles working together.
The muscle which makes the main effort for a given motion is called the prime mover, or agonist.
A synergist is a muscle which assists the prime mover.
An antagonist applies a force opposite to that of the prime mover.
The neutralizer, is present to counteract and correct the direction of pull, if needs be.
A stabilizer is a skeletal muscle that ensures that the joint being moved is properly maintained.
The skeletal muscles that hold these other joints immobile are called fixators.
An activity in which a muscle produces tension without a change in length is called an isometric exercise.
ISO = same
METRIC = measurement
In isotonic exercises, the active muscles change in length.
Several areas of the brain act as coordinators and modulators of the muscle activity of the body. These areas include the cerebellum and the basal ganglia.
The individual motor neuron has its cell body in the brainstem or spinal cord. The actual number of striated muscle fibers contacted by a single motor neuron are together known as a motor unit.
The axial musculature includes the skeletal muscles of the trunk and the upper and lower girdle regions.
The appendicular musculature includes the skeletal muscles of the upper and lower limbs beyond the girdles.
The Golgi tendon organ informs the CNS that the stretch is excessive, the CNS commands the muscle to relax.