Intro Flashcards
Kinesiology
Study of human movement
Focusing on anatomic and biomechanical interactions w/in musculoskeletal system
Why Study Kinesiology?
To understand how individuals move
- to enhance performance
- to decrease injury risk
- exercise equipment and technique, shoes/surfaces, braces/orthoses
- to evaluate pathokinesiology
- functional effect of physical impairments
Kinematics
Concepts that allow us to describe mvt w/o regard to forces that cause mvt (broadly describing motion)
Osteokinematics
Motion of bones relative to cardinal plane (can see what’s happening)
Arthrokinematics
Motion occurring b/w articular joint surfaces (jt mvt) that accompany osteokinematic mvt
Not under voluntary control
Mvt of joint surfaces relative to one another (designed to keep joint surfaces in contact w/ each other)
Occur to maintain jt integrity
Also called “accessory motions” or “joint play”
Kinetics
Allows us to describe why segment moves
Effects of forces on the body
Forces can move, stabilize, deform, injure body
Kinematics - Rotary (Angular) Mvt
Mvt of segment around fixed point
Each point moves in same angular direction across same # of degrees, at same time
Each point will travel different distances depending on their distance from AOR
Ex: shouder
Can measure
Kinematics - Translatory (Linear) Mvt
MTV of segment in straight line
Rectilinear - each point of segment moves thru same direction at same time (in straight line)
-Ex: SC joint
Curvilinear (planar): combo of rotation and translation
- AOR is not fixed (instantaneous center of rotation - ICoR)
- Ex: knee joint
Sagittal Plane (Osteokinematics)
Broken into R/L, M/L
Flex/ext
DF/PF
Forward/backward bending
Frontal Plane (Osteokinematics)
Ant/post direction
Abd/Add
RD/UD
Inversion/Eversion
Lateral flex
Horizontal (Transverse) Plane
IR/ER
Axial rotation
Osteokinematics and Axis of Rotation
During rotation, bones move in plane that is perpendicular to AoR
Typically through convex member or jt
Fixed axis
ICoR - theoretical AoR for joint at given jt position
Degrees of Freedom
of independent directions of mvts allowed at jt
Jt can have up to 3 degrees of freedom (corresponds to cardinal planes)
Proximal Segment Moving about Relatively Fixed Distal Segment Examples
Squat, crunch
Distal Segment Moving about Relatively Fixed Proximal Segment Examples
Seated knee extension, kicking a ball
Kinematic Chain
Series of articulated segmented links
Connected pelvis, thigh, leg, and foot of LE
Ex: squatting
Open Chain Mvt
Distal end of chain is free to move
One Joint can move independent on others
Closed Chain Mvt
Distal end is fixed
Mvt at one jt automatically creates mvt in other joints
Roll (Arthrokinematics)
Multiple points along one rotating articular surface contact multiple points on another articular surface
Slide/Glide (Arthrokinematics)
Single point on one articulating surface contacts multiple points on another articular surface
Rolling convex surface typically involves concurrent, oppositely directed glide
Concurrent roll/glide maximizes angular displaces and minimizes net translation
Spin (Arthrokinematics)
Single point on one articulating surface contacts single point on another articulating surface
Primary mechanism for jt rotation when longitudinal axis intersects w/ jt surface at perpendicular angle
Concave/Convex Rule
Arthrokinematics can be predicted from jt morphology
Convex-on-concave surface mvt - conves member rolls and glides in OPPOSITE directions
Concave-on-conves surface mvt - concave member rolls and glides in SAME direction
Closed Packed Position
Position of most congruency b/w 2 jt surfaces
Ligaments/capsule taut
Minimal accessory mvt
Open (Loose) Packed Position
All other positions
Clinically identified “open packed positions” for each joint
Allows greatest accessory mvt
Often biased toward flex
Forces
Push or pull that results from physical contact b/w two objects (w/ exception of gravity where there is no physical contact)
External - gravity, external load, physical contact (therapist generated)
Internal - w/in body
- Active = muscle
- Passive = tension
Magnitude of Displacement
Degrees or radians
Magnitude of segment can (or does) move through it’s ROM
Vectors
Arrow representing both magnitude and direction
Length = magnitude
Direction = direction of mvt
Represents forces
Muscle Force Vectors
Has orientation, magnitude, point of application
Used to determine efficiency of muscle in developing a moment
Force of Gravity
Acts on each unit of mass
LoG = line of gravity (always toward Earth)
CoG = hypothetical point at center of object’s mass (also known as CoM)
When considering several segments, CoG’s combine and move toward heaviest segment
Change angle - change center of gravity
Center of Mass of Humans
Anterior to S2
W/ rearrangement of segments of body, CoM moves
Effects of External Force and Base of Support
Move CoM over base of support
Newton’s 1st Law: Inertia
Body remains at rest or in uniform motion (moving w/ a given speed and direction) unless acted on by external force to change its state
Inertia: amount of energy required to alter velocity of body
Newton’s 2nd Law: Acceleration
F=ma
If acceleration is constant and force changes, need less force to move a lighter object than something heavier
Newton’s 3rd Law: Reaction
For every action, there is equal and opposite rxn
Linear Force System
Two or more forces w/ same orientation and line of action
Positive (up, forward/anterior)
Negative (down, back/posterior)
Resultant Forces
Two or more segments of one muscle or two muscles w/ common attachment
Ex: quads
Tensile Force
Created by opposite pulls on same object (stretching)
Distraction Force
Pull or mvt of 1 boney segment away from another
Joint Reaction Force
Two segments of joint are pushed together and press back against each other
Compression Force
Two forces that cause joint rxn force
Shear Force
Any force that has action parallel to contacting surfaces and creates/limits mvt b/w surfaces
Friction Force
Potentially exists on object whenever there is contact force on that object
Force and CoM
If force is applied though object’s CoM, linear displacement will occur
If applied force doesn’t pass through CoM, curvilinear mvt will occur
Force Couple
Two force of equal magnitude in opposite direction
Create rotation at point midway b/w 2 forces if ends are free to move
Only one side free to move - create rotation around point of application of one of forces if that point is fixed
Force Couple (Muscle)
2 or more muscles simultaneously produce forces in different linear directions w/ torques that act in same rotatory direction
Moment Arm
Perpendicular distance b/w force and axis of movement/rotation
Shorter moment arm - greater amount of force needed to create mvt
Torque
Strength of rotation (called moment of force)
Internal: muscle
External: gravity
Moment Arm and Angle of Application
Changes in angle of force results in changes to moment arm of force
Moment arm greatest when force is perpendicular to lever
Lever
Convert forces into torques
Functions to produce rotatory torque out of linear force
Consists of rigid body w/ two applied forces and point of rotation
Effort Force (EF)
Force that is producing
Always wins when mvt occurs
Ex: bending elbow - biceps is effort force
Resistance Force (RF)
Force tha is creating opposing force
Ex: bending elbow - gravity is resistance force
Effort Arm (EA)
Moment arm for effort force
Resistance Arm (RA)
Moment arm of resistance force
First Class Lever
Axis of rotation b/w opposing forces
EA may be >,
Second Class Lever
AoR is at end of one bone
External force is closed to AoR than muscle force (internal)
Muscle force has greater leverage than external forces
Very few in human body
Ex: gastroc
Third Class LEver
Axis of rotation is at end of one bone
Muscle force is closer to AoR than external force
External force has greater leverage than muscle force
Most common type in body
Ex: biceps
Mechanical Advantage
Measure of mechanical efficiency of lever
Ratio of internal to external moment arm
When internal moment arm is larger than external moment arm, MA > 1
Magnitude of internal/muscle force can be less than that of Ef and still “win”
Mechanical Advantage of Levers
1st class levers: MA >, 1
3rd class levers: MA < 1
3rd class lever mechanically inefficient
Muscle force must be greater than external force to create equilibrium or mvt
Mechanical Disadvantage
Allows for greater rotation through space
Small force creates large arc of mvt of distal segment
