Kinesiology & Biomechanics

Kinesiology

The study of movement

Biomechanics

The mechanics of human movement

Kinematics

The study of motion
('what' moves)

Kinetics

The effect of forces on the body
('how' it moves)

Translation
(Translatory Motion)

1. Linear motion (straight line/rectilinear, curved line/curvilinear)
2. All parts of the object move the same distance and direction at the same time.
3. Named by the axis that it translates 'along,' or the plane that it translates 'in.'

Linear Motion (2 types)

1. Straight line (rectilinear)
2. Curved line (curvilinear)

Rectilinear Motion

Translatory motion in a straight line

Curvilinear Motion

Translatory motion in a curved line

Rotation
(Rotatory Motion)

1. All parts of the object rotate through the same angle in the same angular direction
(curved path around a pivot axis)
2. Named by the axis that it rotates 'around,' or the plane that it rotates 'in.'

Axis of Rotation

The point where motion of the rotating body is equal to zero

Combined Motion

1. Translation with rotation
2. More often seen in the human body

Path of Instantaneous Center of Rotation
(PICR)

The route followed by the axis of rotation during combined motion.
This can indicate normal or abnormal movement.

PICR Influencing Factors

1. Shape/contour of joint surfaces
2. Ligamentous control
3. Muscle actions

PICR Abnormalites

1. Consequence of influencing factors
2. Abnormal wear/tear on joint structures
3. Can be identified in many joints during clinical exam

Position

Point in space

Displacement

The change in position (linear or angular)

Velocity

The change in position over time (x/t: m/s or rad/s)

Acceleration

The change in velocity over time (v/t: m/s^2 or rad/s^2)

Displacement/Velocity vs. Velocity/Acceleration

1. At max/min in displacement/velocity, velocity/acceleration equals zero.
2. The slope of displacement/velocity equals the instantaneous velocity/acceleration.

Frame of Reference

What is moving relative to what?
(You must specify your reference point and orientation)

Right Hand Rule

When designating a direction of torque, follow the right hand rule.
-Fingers follow the rotation: the thumb points in the direction of momentum
-CCW torque is positive
-CW torque is negative

Local Coordinate System

Used when analyzing one segment with respect to the adjacent segment ("relative").

Global Coordinate System

Used when analyzing motion with respect to the ground or gravity.

Osteokinematics

The motion of the bones relative to the planes of the body (sagittal, frontal/coronal, transverse)
Ex: flexion/extension, abduction/adduction, internal/external rotation

Arthrokinematics

The motion of the bones relative to other bones.
Ex: roll, spin, glide

Roll

Multiple points contact multiple points.

Glide

A single point contacts multiple points.

Spin

A single point rotates on a single point

Convex/Concave Rule

1. A convex articulating surface moves in the OPPOSITE direction of the rolling bone.
2. A concave articulating surface moves in the same direction as the rolling bone.

Degrees of Freedom

1. You can have a maximum of 3 Translatory and 3 Rotatory degrees of freedom (6 total).
2. Available motion is determined by: bone shape, ligaments, the joint capsule, accessory joint structures, and muscle).
3. Total degrees of freedom for a system is the sum of each joint.

Translatory Degrees of Freedom

1. Superior/Inferior
2. Medial/Lateral
3. Anterior/Posterior

Rotatory Degrees of Freedom

1. Sagittal plane (AP axis)
2. Frontal/Coronal plane (ML axis)
3. Transverse plane (SI axis)

Open Chain System

One or more ends of the system are free to move (not fixed).
-One joint can move in isolation of other joints
-Ex: Flexing the wrist

Closed Chain System

Each end of the system is rigidly fixed.
-Movement of one joint necessitates movement of other joints.
-Ex: doing a push up (flexing wrist requires shoulder movement)

Functionally Closed Chain System

Each end of the system is fixed or has a constraint on it.
-May not be rigidly fixed, but is functionally fixed
-Ex: Bench press (your hands can move, but are 'fixed' by the amount of weight you're holding; i.e. they can't move much)

Close-packed position

The joint position of maximum congruency (best fit).
-Ligaments and capsules are taut
-Minimal accessory movement allowed
-Most stable joint position

Loose-packed position

The joint position of loosest fit.
-Ligaments and capsules slackened
-Increased allowance of accessory movements
-Less congruent

Force

1. Magnitude
2. Spatial orientation
3. Direction
4. Pont of application

Internal Force

A force within the body:
1. Active: Muscle
2. Passive: Periarticular connective tissue (e.g. ligaments, joint capsules, etc)

External Force

A force outside the body:
1. Gravity
2. External load (weight)
3. Friction

Muscle Force

Magnitude: CSA, # motor units active, strength of contraction
Spatial Orientation: Origin to insertion
Direction: Normal or reverse action

Connective Tissue Force

Magnitude: As much force as is required
Spatial Orientation: Connection to connection
Direction: Opposite of the pull
Point of application: The origin or insertion

Joint Reaction Force

Magnitude: As much force as is required
Spatial Orientation:
Direction: Compression, distraction, shear
Point of application: @ axis of rotation

Center of Mass

The point at which all the mass of an object can be considered to be concentrated; the balance point of an object.
CM=(m1x1+m2x2+m3*x3....)/(m1+m2+m3...)

Anthropometry

The process of modeling CoM segments

Base of Support

Surface area that a person's mass is distributed throughout (stability is determined by whether the CoM falls within the base of support, and the overall width of the base)

Friction

1. Friction resists movement between contacting surfaces.
2. It's magnitude depends on the normal force, and the material each surface is made of.

Torque
(Moment of Force)

Rotational force = applied force * moment arm (perpendicular distance between the force and the axis of rotation)

-Muscle produces an internal torque at a joint, external load produces an external torque.

Moment Arm

The perpendicular distance between the force and the axis of rotation.

Force/Displacement Trade-off

If moment arm is close to the axis: A large force is required, but a small muscular displacement will result in a large angular displacement.

If moment arm is far from axis: Less force is required, but the muscle must contract further to produce similar angular displacement.

Work

Force applied over a distance (W=F*x)
-Work is positive if displacement is in the direction of the force.
-Work is negative if displacement is in the opposite direction of the force.

Energy

The ability to perform work

Power

The rate at which work is done (P=work/time; P=Fv; P=torqueangular velocity)

ex: If torque/moment are in the same direction as the angular velocity, a graph of work should be positive

Momentum

Mass * velocity:
1. Linear momentum = m*v
2. Angular momentum = Iw (moment of inertiaangular velocity)

Conservation of Momentum

Momentum is always conserved within a system (i.e. the total momentum in any direction remains constant unless some external force acts on the system in that direction)