Principles of Kinesiology and Biomechanics

What is Kinesiology?

The study of anatomy and mechanics in relation to human movement.

Anatomical Position

Refers to the specific orientation of the human body that serves as the universal reference point for describing anatomical structures.

-Body is upright and facing forward.

-Arms are adducted, with forearms supinated.

-The legs are parallel, with feet flat on the ground and facing forward.

-The head is level, and the eyes are directed straight ahead.

Superior

Above

Inferior

Below

Cranial

Direction of the skull

Caudal

Beneath or toward the tail

Ipsilateral

Same side of the body

Contralateral

Opposite side of the body

Medial

Toward Midline

Lateral

Away from Midline

Proximal

Toward the Trunk

Distal

Away from the Trunk

Radial

Toward the radius bone (thumb side)

Ulnar

Toward the ulna bone (pinky side)

Sagittal plane

-Divides the body into right and left sides

-Midsagittal plane in the center of the body (midline)

Frontal plane

-AKA: Coronal plane

-Divides the body into anterior and posterior portions

Transvers plane

Divides the body into inferior and superior portions

Frontal axis

-Medial to lateral

-Flexion and Extension

Sagittal axis

-Anterior to posterior

-Abduction and Adduction

Vertical axis

Inferior to superior

Internal and External Rotation

Kinetic Chain

Interdependent movement of the segments or joints of the body (Closed/Open Chains).

Kinetic Chain: Closed Chain

-Functional movement

-Proximal joints moving in relation to fixed/distal segment

-Promote stabilization

Kinetic Chain: Open Chain

-Free movement of distal segment in space

-Allows joints to move together OR independently of others

-Promotes mobility

Biomechanical Properties of Body Tissues

Examine the structure, function, and motion of the biological systems that make up a living organism.

Bone

Made of collagen and calcium

Cortical bone

-Greater mineral content than collagen

-Shaft of long bones

-Rigid support

Cancellous (spongy) bone

-Higher collagen content

-Found in marrow cavity and at end of long bones

Articular (hyaline) cartilage

-Covers ends of long bones

-Dense connective tissue to absorb force between bones

-Multiple layers

Ligaments

-Connect bone to bone

-Joint stability

Tendons

-Connect muscle to bone

-Transfer force

Joint capsule

-Dense fibrous sleeve around synovial joint

-Passive stability

-Contains synovial fluid

Aponeurosis

-Fibrous insertion that connects adjacent muscles

Cardiac Muscle

-Forms muscular components of heart (myocardium)

-Striated and in segments

-Cardiac Muscle fibers are interconnected allowing the cells to contract in a wave like pattern allowing the heart to pump

Smooth Muscle

-Involuntary Muscle

-Internal Organs

-Nonstriated

-Contracts slowly and automatically

Skeletal Muscle

-Moves bones of skeleton, supplying force for purposeful movement

-Striated and alternating bands of fibers

Motor Control

A single muscle is made up of many moto units that send sperate all-or-none signals to sarcomeres

A motor unite includes:

-A motor Neuron (Nerve Cells)

-The muscle fibers it controls

Strong Contraction

Many motor units firing

Weak Contraction

Few motor units firing

Muscle tone

baseline tension at rest and present even when relaxed.

comes from low-level motor unit activity

Normal Muscle Tone

-Smooth resistance to movement

-Allows for efficient occupational performance

Hypotonia

Low Muscle Tone

Caused by loss or interruption of nerve input

Muscle feels limp, soft, and lacking resistance

Severe impact on function

Hypertonia

High Muscle Tone

Increased muscle tone and caused by unregulated CNS signals

Signs are stiffness, increased resistance to stretch, and poor voluntary control

Severe impact on function

Muscle Spindles

-Located within the muscle fiber

-Signal changes in muscle length

-Serves to protect muscles-Muscle contraction

-Contributes to proprioception

Golgi Tendon Organs

-Located within the tendon

-More sensitive to tensile focus

-Protective reflex against over stretching-Muscle relaxation

-Contributes to proprioception

Slow-Twitch (Type I)

Low force, long duration, fatigue resistant, important for posture and endurance tasks.

Fast-twitch (Type II)

High force, quick contraction, fatigue quickly, important for rapid movements and precision tasks.