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Fundamentals of KinesiologyLecture 05 Professor Berthet

Apparel Technical Design

Fundamentals of

Biomechanics

Terminology in Biomechanics


& The Description of Human Movement

(Ch. 10 & 11)

Mechanics● Area of scientific study that answers the questions, in reference to forces

and motion ●What is happening? ●Why is it happening? ● To what extent is it happening?

● Deals with force, matter, space & time.

● All motion is subject to laws and principles of force and motion.

Biomechanics● The study of mechanics limited to living things, especially the human

body.

● An interdisciplinary science based on the fundamentals of physical and life sciences.

● Concerned with basic laws governing the effect that forces have on the state of rest or motion of humans.

The Study of Biomechanics

Biomechanics

Biology Mechanics

Anatomy/ Physiology Kinematics Kinetics

emg* Motion capture* Force plate/ transducer*

Structure FunctionStatics

(zero or constant velocity)

Dynamics (acceleration)

Statics (ΣF=0)

Dynamics (ΣF≠ 0)

* Tools used to collect biomechanics data in laboratories

Statics and Dynamics

Statics: all forces acting on a body are balanced

ΣF = 0 – The body is in equilibrium.

Dynamics: deals with unbalanced forces

ΣF ≠ 0 – Causes object to change speed or direction. ● Excess force in one

direction. ● A turning force.

● Principles of work, energy, & acceleration are included in the study of dynamics.

● Biomechanics includes statics & dynamics.

Kinematics and KineticsKinematics: geometry of motion ● Describes time, displacement, velocity, & acceleration. ● Motion may be in a straight line or rotating.

Kinetics: forces that produce or change motion.

Linear – motion in a line.

Angular – motion around an axis.

Kinematics and Design

3D printed dress

Motion: Relative MotionMotion is the act or process of changing place or position with

respect to some reference object. ● At rest or in motion depends totally on the reference. ● Sleeping passenger in a flying airplane: ● At rest in reference to the airplane. ● In motion in reference to the earth.

Cause of Motion●Force is the instigator of movement.

●Force must be sufficiently great to overcome the object’s inertia (resistance to motion)

●Force relative to resistance will determine if the object will move or remain at rest.

Kinds of Motion●2 classifications of movement patterns: ●Linear or translatory ●Angular or rotary

●Although the variety of ways in which objects move appears to be almost limitless, careful consideration reveals only

Translatory Movement (linear) ●An object is translated as a whole from one

location to another.

●Rectilinear: straight-line progression

●Curvilinear: curved translatory movement

Rectilinear motion

Curvilinear motion

Circular Movement (curved linear)● A special form of curvilinear motion.

● Object moves along the circumference of a circle, a curved path of constant radius.

● The logic relates to the fact that an unbalanced force acts on the object to keep it in a circle .

● If force stops acting on the object, it will move in a linear path tangent to the direction of movement when released.

Angular, or Rotary, Motion

● Typical of levers, wheels, & axles

● Object acting as a radius moves about a fixed point.

● Measured as an angle, in degrees.

● Body parts move in an arc about a fixed point.

Angular or Rotary Motion?

●Circular motion describes motion of any point on the radius.

●Angular motion is descriptive of motion of the entire radius.

●When a ball is held as the arm moves in a windmill fashion ● ball is moving with circular motion. ● arm acts as a radius moving with

angular motion.

Other Movement Patterns● Combinations of linear & angular motion are called general motion

● Angular motions of forearm, upper arm & legs.

● Hand travels linearly and imparts linear force to the foil.

Other Movement Patterns

●Most joints are axial.

●Segments undergo primarily angular motion.

●Slight translatory motion in gliding joints.

Fig

Kinds of Motion 
Experienced by the Body●Linear movement when the body is acted

on by the force of gravity or a linear external force.

Kinds of Motion 
Experienced by the Body

● General motion ● e.g. forward and backward rolls on

ground

● Rotary motion ● e.g. spinning on ice skates

● Curvilinear translatory motion ● e.g. diving and jumping

● Reciprocating motion ● e.g. swinging on a swing

Factors Modifying Motion● External factors ● Friction helps a runner gain traction, but hinders the rolling of a ball.

● Air resistance or wind is indispensable to the sailboat’s motion, but may impede a runner.

●Water resistance is essential for propulsion, yet it hinders an objects’ progress through the water.

Factors Modifying Motion

● Internal or anatomical factors: ● Friction in joints; tension of antagonists,

ligaments & fasciae; anomalies of bone & joint structure; atmospheric pressure inside joints; and presence of interfering soft tissues.

● Major problems in movement are: ● How to take advantage of these

factors. ● How to minimize them when they are

detrimental to the movement.

Critical Thinking & Application of Knowledge

Define the Type of Motion of the Planets?

What would happen if the gravitational force of the sun ceased to be exerted on the planets?