Ch. 1 Biomechanics and Related Movement Disciplines

KH 3600 Biomechanics
Biomechanics and Related Movement Disciplines

Biomechanics: the physics (mechanics) of
motion produced by biological systems.
More specifically…a highly integrated field of
study that examines the forces acting upon,
within, and produced by a body.

Integrates biological characteristics with
traditional mechanics.
Mechanics: the branch of physics specifically
concerned with the effect of forces and energy on
the motion of bodies.

Mechanics
Statics: the study of systems in a state of
equilibrium.
▪ At rest or in a constant state of motion.
Dynamics: the study of systems in a state of
accelerated/changing motion.

Kinematics: study or description of the spatial and
temporal characteristics of motion without regard
to the causative forces.
e.g., displacement and velocity
Kinetics: study of forces that inhibit, cause,
facilitate, or modify motion of a body.
e.g., friction, gravity, and pressure

Example: A soccer player injures his foot
while trying to outmaneuver an opponent,
and possibly because he is too old to be
playing soccer.
▪ Kinematic perspective: How fast was the soccer player
moving at the moment of injury?
▪ Kinetic perspective: How much force was absorbed by
the body when making a quick change in direction?

Outside of sport, biomechanists also examine
more common human motions, such as
walking.
Example: Walking infant
▪ Kinematic perspective: What is the length of the infant’s
strides?
▪ Kinetic perspective: Why does the infant walk in this
manner?

Describe a movement in kinematic terms

Biomechanics is about movement:
Exercise Physiology: movement is caused by
contraction of skeletal muscle.
Motor Control: mechanics used by the nervous
system to control and coordinate movements.
▪ Motor development
▪ Motor learning

Biomechanics is about movement:
Ergonomics: analyzing the work environment and human‐
machine interaction.
Physical therapy and sports medicine:
prevention/treatment/rehabilitation from acute and
chronic injuries that result from human motion.
Pedagogy and coaching: try to modify movement
behaviors.
Functional anatomy: no matter the movement‐related
discipline, an in‐depth knowledge of the human body is a
must.

Exercise requires the cooperation of all the
body systems:
Neurological system initiates muscle contraction
to move the skeletal system.
▪ Increased activity of the muscular system requires a
large amount of energy (ATP) to be produced by the
metabolic system.
▪ To make ATP, oxygen and food fuel are needed.
Transported within the body by our cardiovascular system.

The link between exercise physiology and
biomechanics is the neuromuscular system.
Muscles are the metabolic machines that cause
motion of the skeletal system.
▪ Muscles are under the control of the nervous system.
▪ Muscles are a kinetic factor that affects kinematic
values.

For movement, muscles produce force, and
forces are the realm of kinetic analysis.
As muscular strength changes, so do the
kinematics of movement.

Motor = movement
Motor behavior is defined by three sub‐
areas:
1. Motor control: how the nervous system controls
coordinated skill performance.
2. Motor development: how motor control changes
over time.
3. Motor learning: how humans learn motor skills.

Depending on the movement task, humans are
believed to rely on one of two control systems:
Open‐loop: movements that happen so quickly the brain
doesn’t have time to receive feedback to influence the
current performance.
Closed‐loop: movements that can be changed during a
performance as the brain receives sensory feedback from
the eyes, ears, and proprioceptors throughout the body.

Coordinated movement must be controlled
by the nervous system.
In some cases the skills are open‐loop,
whereas other skills are closed‐loop.
The internal kinetics and resulting kinematics may
vary.

From birth to advanced age, the body is in a
state of dynamic state of change.
The primary motor activities are evident at
birth and are not voluntary.
They are reflexive behaviors that are designed to
gather information and protect the body.
Voluntary motion begins only when the
nervous and muscular systems are ready.

Kinematics and kinetics of all skills change
with motor development:
Until puberty, girls and boys differ very little in
structure and physiology.
Changes that occur during and after puberty can
have positive and negative effects on athletic
performance.
▪ i.e., Michael Jordan was cut from his high school
basketball team as a freshman, but he excelled once he
adapted to his new size and strength.

The process of learning begins in the early stages of
infancy.
Early learning in movement is a trial‐and‐error
process in which infants and toddlers attempt new
activities.
Motor learning takes into account the structural and
physiological changes through the lifespan, but
focuses primarily on neurological aspects of
attaining and retaining motor skills.

Ergonomics: a discipline concerned with
interaction of humans and machines and with
the factors that influence that interaction.
Ergonomists attempt to improve the human‐
machine system.

Biomechanics and ergonomics are so closely
related that ergonomics is sometimes
referred to as occupational biomechanics.
Many kinetic factors affect work tasks: muscle
forces, weight of equipment, vibrations, and
surface textures.

The kinematics of the work task can be
analyzed by the ergonomists to estimate the
effects of kinetic factors upon the human‐
machine interface.
Based upon the findings of biomechanical
analysis, the ergonomists can then make
informed decisions to improve the human‐
machine system.

Biomechanical analysis can then be used to
observe the resulting kinetic and kinematic
changes to verify the effectiveness of the
intervention.

Physical therapy: the field dedicated to preventing,
evaluating, and treating movement abnormalities.
Disordered movement may be caused by injury,
disease, muscular imbalance, or congenital
conditions.
Abnormal motion at one joint is often associated
with abnormal motion at another joint.

This abnormal motion (measured
kinematically) is likely associated with
abnormal forces acting upon that structure
(kinetics), leading to further motion
abnormality.
Physical therapists must be familiar with
biomechanical principles to properly
recognize and diagnose the underlying cause
of disordered movement.

Sports medicine: focuses on preventing and
immediately treating injuries that occur during
sports and on rehabilitating athletes after such
injuries.
Preventing injury may require such methods as bracing
and taping, both of which can affect normal human
motion.
Biomechanics can help the athletic trainer
understand the mechanism of injury.

The common objectives of quality teaching
and coaching are to encourage learning and
enhance performance.
Pedagogy in physical education and sport
draws upon several fields to form the basis of
scientific principles for teaching and
coaching:
Psychology, sociology, motor behavior, anatomy
and physiology, and biomechanics.

Adapted physical education: the process of
teaching movement activities to children
with disabilities.
Understanding how the human body moves
and learns enables the teacher to adapt
movement activities that can help people
with a variety of disabilities become
competent, lifelong movers.

Defined: Biomechanics, Mechanics, Statics,
Dynamics, Kinematics, Kinetics
Biomechanics in linked with many other
disciplines, but is the best and most
important of all of them.