Section III. SOME SKELETOMUSCULAR MECHANICS
The skeletal and muscular systems of the body work together to produce motions
and locomotion of the body. All of these actions are mechanical in nature. They utilize
the various mechanics as studied in physics.
a. Vectors. The various forces produced by contracting muscles have specific
direction and magnitude. As such, these vectors or forces when plotted are
represented by arrows whose length corresponds to the magnitude of the force and
whose direction corresponds to the direction of the force.
b. Lever Systems. 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
third class of lever (Figure 5-2) is the most common.
Figure 5-2. Types of lever systems.
c. 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.
This is achieved by having the muscle's tendon go around a bony eminence in the same
way as a rope goes around a single pulley.
d. Pendulums. During locomotion, the body uses several pendulums in the
swinging of the upper and lower limbs.