introduction to kinesiology (movement science)

kinesiolgy

the study of movement

• three primary areas

• 1) anatomy

• 2) physiology

• 3) biomechanics

biomechanics

application of mechanical principles in the study of living organisms

mechanics

analysis of action of force

• broken into kinematics and kinetics

kinetics

the effects of forces that act on a body

• a push or pull that produces, modifies or stops movement

first law of intertia

a body that remains at rest/motion will stay at rest/motion unless acted on by an external force

second law of acceleration

acceleration of a body is directly proportional to the force causing it and takes place in the same direction in which the force acts

• inversely proportional to the mass of the body

  • F = ma

third law of action-reaction

for every force there is an equal and opposite directed force

kinematics

the motion of a body w/o regard for the forces or torques that cause that motion

• broken into translation and rotation

translation

linear motion

• broken into rectilinear and curvilinear motion

rectilinear motion

motion along a straight line

• ex: box pushed along the ground, COM during a sprint

curvilinear motion

motion along a curved path

• ex: path of ball in air, COM path during long jump, diver

rotation

angular motion

angular motion

assumption is a rigid body moves in a circular path around some pivot point or axis of rotation

• all points rotate simultaneously

  • ex: ball spinning in air, gymnast swinging around high bar

active movements

stimulated by muscle contraction

passive movements

stimulated by a source other than an active muscle contraction

• ex: push or pull from another source, gravity

osteokinematics

the motion of bones/segments relative to the 3 cardinal planes of the body

• default to planes of motion standing in anatomic position

• sagittal, frontal and transverse plane

arthrokinematics

motion that occurs between the articular surfaces of joints

sagittal plane

divides the body into left and right

• terms medial and lateral relate to this plane

• perpendicular to ground

• actions that occur: flexion/extension, dorsiflexion/planterflexion

frontal plane

divides the body into front and back portions

• terms anterior and posterior relate to his plane

• actions: ABduction, ADduction, lateral flexion, eversion/inversion

transverse plane

divides the body into top and bottom portions

• terms superior and inferior relate to this plane

  • actions: internal and external rotation, axial rotation a

axis of rotation

the reference line around which angular motion occurs

• segments move in a plane of motion perpendicular to an axis of rotationve

vertical axis

runs inferior to superior

• formed by the intersection of the sagittal and frontal planes

• movement about the transverse plane

• motions that occur: rotation

medial-lateral axis (frontal)

runs horizontally from left to right

• intersection of the frontal and the transverse planes

• movement about the sagittal plane

  • motions that occur: flexion/extension

anterior-posterior axis (sagttial)

runs horizontally from anterior to posterior

• intersection of the sagittal and transverse planes

• movement about the frontal plane

• motions that occur: ABduction/ ADduction

center of mass

a distribution of mass in space is the unique point where the weighted relative position of the distributeddegr mass sums to zero

• generally just anterior to the sacrum

• helps us understand movement, balance and stability

degrees of freedom

the # of independent directions of movement permitted at a given joint

• maximum # of 3 DOF

accessory motion

the slight passive translations that occur in most joints

• driven actively by muscle or passively bc of natural laxity within a jointr

reference point

specific anatomical landmark or position used to describe, measure, and track the movement of a bone relative to the body or the environment

• proximal segment moving on relative fixed distal segment

  • 1) ex: performing a squat

• ex: distal segment moving on relative fixed proximal segment

  • 2) performing a seated leg extension

open kinematic chain (OKC)

when the distal segment IS NOT fixed to the earth or other immovable object

• distal segment is free to move

  • ex: bicep curl, leg extension

closed kinematic chain (CKC)

when the distal segment IS fixed on the earth or other immovable object

• distal segment is NOT free to move

• ex: squat

external forces/loading

act on an object as a result of interaction w/ environment

• contact (ex: ground reaction force)

• non-contact forces (ex: gravity)

internal forces/loading

act within the object or system

• hold system together when acted on by external forces

• ex: muscle/ligament tension

characteristics of force

vector quantity

• key features: magnitude, direction, point of application, orientation angle

normal force

force acting perpendicular to surface of object

tangential force

force acting parallel of surface of object

net force

a single resultant force derived from the vector composition of all acting force

torque/moment

an angular force that causes a segment to turn around an axis

T = F*d

moment arm

the shortest perpendicular distance from the axis of rotation to the line of action of a force