KIN 222 - Midterm 1

Biomechanics

Biomechanics

study of structure and function of biological system by means of the methods of mechanics

Kinematics

study of motion WITHOUT regard to the forces that cause it

Kinetics

study of forces

Quantitative analysis definition and example

• numerical evaluation of motion based on measurement

• hip flexes X degrees, knee flexes Y degrees

pros/cons of quantitative analysis

pros: objective, accurate, specific cons: expensive, difficult to get data (special training and equipment required), difficult to apply, need norms

Qualitative analysis definition and example

• non-numerical evaluation of motion based on observation

• hip flexes, knees flex

pros/cons on qualitative analysis

pros: cheaper, time efficient cons: subjective, general, less accurate, experience changes results

statics is the evaluation of objects in a state of ...

evaluation of objects in a state of equilibrium - at rest or constant velocity

dynamics is the evaluation of objects ...

evaluation of objects that are not in a state of equilibrium - acceleration

Evaluating a runner at the start position would be static or dynamic?

static

Evaluating a runner after the start position would be static or dynamic?

dynamic

Scalar definition and examples

• can be described by magnitude

• distance, speed, mass, volume, energy

Vector definition and examples

• can be described by magnitude and direction

• displacement, velocity, acceleration, force

linear motion definition and example

• straight or curved motion where all parts move the same distance in an equal amount of time

• ball travelling after a throw

Angular motion definition and example

• motion about an axis of rotation where regions do not move the same distance in an equal amount of time

• a rotating sprinkler

Gait definition. What are the two primary gait patterns?

• particular pattern of footfalls that are used in locomotion

• walk and run

Describe the gait cycle events

Stance Phase (60% of the stride): Heel #1 makes contact with ground in frontward position (double support). All weight transfers to #1 (single support) as hip extends. Heel #2 makes contact with ground (double support).

Swing Phase (40% of the stride): All weight transfers to leg #2(single support). Leg #1 swings from hip extension to flexion

Step

process of moving one limb forward

stride

porcess of making one step with each foot

stride time

time it takes to complete one stride

stride length

distance between heel strikes of the same foot

stride velocity

• vector so includes changes in direction

• stride length/stride time

walking speed

• scalar

• distance/time

stride cadence (this is a frequency)

1/stride time

If time decreases what happens to stride velocity and walking speed?

increases

What is the relationship between stride velocity and stride length, and stride velocity and cadence? What does this relationship show?

There is a linear relationship (increase stride length = increase stride velocity, increase cadence = increase stride velocity). This shows the preferred speed-step length relationship where the pace chosen is the pace with the least metabolic cost

What happens to stride length and cadence as velocity increases during running?

The linear relationship held at walking speed does not continue. Stride length plateaus and cadence increases

What is the difference between a walk and a run?

Walk:

• always one foot in contact with ground

• contact pattern: 1, 2,1

Run:

• an airborne phase between single supports

• contact pattern: 1, 0, 1

What is considered to be a functional vital sign?

Walking speed. It is used to identify health issues and can predict adverse health outcomes

displacement

• change in an objects position from initial to final location

• vector = final position - initial position

velocity

• rate of change of an objects displacement over a particular time interval

• vector = displacement/time or (final position- initial position)/ (final time - initial time)

when velocity = 0

object not moving or object changing direction

Distance

• total length travelled

• scalar

when distance = displacement

object moves in straight line

Displacement is always _____ than or _____ to distance

less than or equal

speed

• distance travelled over time or rate of distance travelled over time

• scalar = distance/time

average velocity

average change in displacement over a time interval

instantaneous velocity

rate of change of displacement at a particular instant in time

what happens to displacement when velocity increases and time is constant?

displacement increases

What happens to displacement when time increases and velocity is constant

displacement increases

On a displacement over time graph, what represents velocity? A positive velocity is indicated by? A negative velocity is indicated by? What point on a graph would indicate that the object is changing direction? The greater the slope = ? Lesser?

• slope

• positive slope (line going upward)

• negative slope (line going downward)

• when slope changes from pos to neg or neg/pos. This indicates velocity = 0

• greater velocity

• lesser velocity

How do you calculate velocity on a displacement over time graph?

slope = rise/run

What motion is each segment represent?

1. Accelerating walking in positive direction (speeding up)

2. decelerating walking in positive direction (slowing down)

3. y = 0 stop or change in direction

4. Accelerating in negative direction

5. Decelerating in negative direction

6. stop

How is displacement calculated on a velocity vs time graph?

By taking the area of the graph and subtracting positive and negative displacements. Calculate area of a triangle = 0.5 x base x height

Describe the motion that each velocity vs time graph illustrates

A: slow acceleration , fast acceleration , fast deceleration, slower deceleration B: deceleration + direction, change direction, acceleration in - direction C: constant deceleration to a stop D: moving at a constant velocity

Acceleration

• measure of the rate of change of velocity with respect to time

• vector quantity

True or False. A change in velocity does not always indicate there is acceleration?

False. If there is a change in velocity (either magnitude or direction) then there is acceleration

If acceleration and velocity are in the same direction

velocity will increase

If acceleration and velocity are in opposite directions

velocity will decrease until the object stops or changes direction

What type of path do projectiles follow?

Parabolic

What are the vertical and horizontal accelerations of projectiles

• vertical -9.81 m/s^2

• horizontal 0, remains constant

If you kick a ball upwards at 0, 45, and 90 degrees, which will have the greatest vertical and horizontal displacement?

0

• no vertical displacement

• horizontal displacement but slows down from surface friction

45

• less vertical displacement than kicking upwards at 90

• greatest horizontal displacement

90

• greatest vertical displacement

• no horizontal displacement

Describe the time and horizontal displacement of a projectile with equal launch and landing height

• time from launch to apex is equal to time from apex to landing

• horizontal displacement equal from launch to apex and apex to landing

Describe the time and horizontal displacement of a projectile with a higher launch point than landing point

• time from launch to apex will be shorter than apex to landing

• horizontal displacement will be shorter from launch to apex than apex to land

Describe the time and horizontal displacement of a projectile with a lower launch point than landing point

• time from launch to apex will be longer than apex to land

• horizontal displacement from launch to apex will be longer than apex to land

When are velocity formulas inaccurate?

when the object is undergoing acceleration

If a person is not undergoing acceleration, what formula can be used and will be accurate

average velocity formulas can be used

frontal plane

anterior and posterior halves

transverse plane

inferior and superior portions

saggital plane

left and right sides

Anteroposterior axis

• goes through the body from front to back

• associated with frontal plane

Longitudinal axis

• runs from top to bottom

• associated with the transverse plane

Mediolateral axis

• side to side

• associated with sagittal plane

what are degrees of freedom? What is the max degrees of freedom? How many degrees of freedom do joints have?

• number of independent movements an object can perform

• max 6 degrees of freedom (3 rotations, 3 translations)

• joints have 1-3 however, translation also occurs at many joints, increasing their degrees of freedom

Shoulder joint (Glenohumeral) - what type of joint and how many degrees of freedom?

• ball and socket

• 3 df

Name the glenohumeral joint movements and what plane/axis they occur in

Flexion/extension

• saggital and mediolateral

Abduction/abduction

• frontal and anteroposterior

Medial and lateral rotation

• transverse plane longitudinal axis

Superior and inferior radioulnar joints - what type of joint and how many degrees of freedom

• pivot joint

• 1 df

ulnarhumeral and radiohumeral joint - what type of joint and how many degrees of freedom

• hinge

• 1 df

Acetabulofemoral - what type of joint and how many df?

• ball and socket

• 3 df

Describe the movements of the hip joint and what plane/axis they occur in

Flexion/extension

• sagital

• mediolateral

Adduction/abduction

• frontal

• anteroposterior

medial/lateral rotation

• transverse

• longitudinal

Knee (Tibiofemoral) joint - what type of joint and how many df?

• double condyloid (modified hinge)

• 2 df

• significant translation accompanies knee joint motion

Name the movements of the knee joint and what plane/axis they occur in

Flexion/extension

• sagital

• mediolateral

Medial/lateral rotation

• transverse

• longitudinal axis

Ankle (talocrural) joint - what type of joint and how many df?

• hinge

• 1 df

ankle joint movements and plane/axis

dorsi/plantar flexion

• sagital

• mediolateral

What symbols are used for angular kinematics?

• theta: angular displacement

• omega: angular velocity

• alpha: angular acceleration

Counter clockwise rotations are? Clockwise?

• positive

• negative

Angular displacement definition. Vector/scalar? Formula

• differences between the initial and final orientation of a rotating object

• vector = final orientation - initial orientation

Angular distance definition. Vector/scalar?

• total of all angular changes measured following a rotating segments exact path

• scalar

Angular displacement cannot be greater than _____, angular distance can be ______

• 360 degrees

• any value

Angular velocity definition. What is it analogous to? Formula.

• rate of change of angular displacement over time

• analogous to linear velocity

• w = (theta final - initial)/time

The steepness of an angle vs time graph determines the? The direction of the slope determines the?

• magnitude of angular velocity

• direction of angular velocity

On an angle vs time graph, a change in the direction of the slope indicates a?

a change in the direction of movement

on an angular velocity vs time graph, a change in the sign of angular velocity indicates

a change in direction of movement

Angular motion definition

• evaluation of an objects motion around a fixed axis

• all parts move through the same angle, but do not have equal linear distance

Name 3 techniques used to measure angular motion

• Video: camera captures frames/sec

• Motion capture: uses specific dots/points on body, then is input into computer

• goniometry: measures the joint angle with specific instruments ex. the bendy wire

local reference system

axes are aligned with a segment and intersect at the joint center

global reference system

axes are aligned with the vertical and horizontal relative to the environment (lab)

How are absolute segment angles calculated?

• use the trigonometric relationship of tangent

• the distal end coordinate values are subtracted from the proximal end coordinate values

• theta = [(y prox - y dist)/ (x prox - x dist)]

What is a relative joint angle? What reference system is used? Where is the vertex located?

• the angle between the longitudinal axis of two segments. Defined as the angle of one segment relative to another segment

• local reference system

• at joint

Relative (joint) angle conventions - a system of lower limb conventions has been proposed for two dimensional sagittal plane rotation of the _____, _______, and ______ joints.

This system uses the _______ angles of the trunk, thigh, leg, and foot to calculate relative joint angles

With this system, it is assumed that the _____ side of the body is captured

• hip, knee, and ankle

• absolute

• right

The relative hip angle is based on the absolute angles of the?

thigh and trunk

When the hip angle is positive, the hip is in what position? Angle = zero? Angle is negative?

• flexed (because it is to the right of the vertical axis)

• neutral

• extended (because it is left of the vertical axis)

What is the formula for calculating relative hip angle

theta hip = theta thigh - theta trunk

The relative knee angle is based on the absolute angles of the?

thigh and leg

When the knee is in a flexed position the angle is? When the knee is in the extended position? Hyper-extended?

• positive (extend the shin line upwards and it will end up in the positive right quadrant)

• neutral

• negative (extend the shin line upwards and it will be in the negative x quadrant)

What is the formula for calculating relative knee angle?

theta knee = theta thigh - theta leg

The relative ankle angle is based on the absolute angles of the

leg and foot

When the angle is positive, the ankle is in what position? Angle = zero? Negative?

• plantarflexed

• neutral position (ex standing)

• dorsiflexed position

What is the formula for relative ankle angle?

theta ankle = theta leg - theta foot + 90

Define angular acceleration. It is analogous to?

• rate of change of angular velocity over time

• analogous to linear acceleration