Balance and stability are used ______?

Interchangeably

Resistance to disruption of equilibrium

Stability

A persons ability to control equilibrium

Balance

For a system to be stable and for one to maintain balanced two conditions must be met? What does this basically mean?

1. All linear forces acting on the body must be balanced
2. All rotary forces (torques) must be balanced

Basically, the sum of all forces acting on the body must equal zero

All objects at rest are in equilibrium

Equilibrium

3 Types of equilibrium?

1. Stable Equilibrium
2. Unstable Equilibrium
3. Neutral Equilibrium

The center of gravity must be _____ in order to disrupt object? The more the center of gravity needs to be raised, the more ____ required to disrupt object? As a result the object is more ______? Where might we see this in sport/exercise?

raised

effort

stable

Athletic stance to lower COG

When the center of gravity starts high and drops to a lower point? It requires less ____ and
As a result, it is less _____?

Unstable Equilibrium

energy

stable

Object’s center of gravity does not change when the object’s position changes? Give an example?

Neutral Equilibrium

Walking….changes a little but not much

What are the 3 factors that can influence balance/stability? Describe the subcategories under each?

Physiological Factors- Proprioception

Body Characteristics and/or Positioning- Center of gravity
Base of support
Mass of the body

External Factors- Environmental Conditions

Proprioception is a term coined in ____?

1906

The ability to sense where our body is in space? Its a sense of ____ and _____? It is described to be _____?

Proprioception

Sense of position & balance

Cognitive/subconscious

Kinesthesia is a term coined in _____? “kenein” = _____?
“aesthesis” = _____?

1880

to move

sensation

Movement of body

Kinesthesia

What is behavioral kinesthesia?

– learn movements so you know how they feel for future reference

“Presently, “kinaesthesia” and “proprioception” are used practically synonymously to indicate the capability to appraise the configuration and movements of an __________.”?

organism’s body parts

Proprioception provides information on the ____ and _____ of movement of one body part relative to another? What is an example of this? Who has better proprioception than average individuals?

location

rate

Close eyes and touch nose example…we know general location of space

Elite athletes

Proprioceptive sense informs.....
The degree to which our muscles are being ______
The amount of tension created in the ______
_____ in joint position
The orientation of the ____ relative to the ____ and environment

contracted

tendons

Change

head...body

Proprioception is often divided into what 3 senses?

Sense of Tension (resistance)

Sense of Movement

Sense of Joint Position

The ability to appreciate force generated within a joint

Sense of Tension (resistance)

The ability to appreciate joint movement (duration, direction, amplitude, speed, acceleration, timing of movements)

Sense of Movement

The ability to perceive a presented joint angle and reproduce specified joint angles …close eyes, can you put your elbow at a 90 degree angle?

Sense of Joint Position

Cumulative neural input to the CNS from a variety of specialized nerve endings

Proprioception

Name 4 types of Mechanoreceptors?

Skeletal Muscle & Joint Receptors
Cutaneous & Fascial Receptors w/in skin

Proprioception also obtains information from what 2 things?

Vision
Vestibular

Sensory input received from mechanoreceptors are integrated and appreciated at what three levels of the CNS?

Spinal level

Brain Stem

Higher levels such as cerebral cortex + cerebellum

Can provide direct motor responses in the form of reflexes…reflex reaction

Spinal level

Brain Stem:
Integration of ______ information with visual and vestibular inputs to aid in control of typical ______ patterns, continual output to maintain _____ + _____

afferent

movement

balance & posture

Conscious awareness of movements – voluntary movements

Higher levels (cerebral cortex & cerebellum)

Muscle spindle provide______ at all times? Why is this special?

continual feedback

(only one that does this)

What do muscle spindles do? Within muscle fibers as _______
Automonic with _____ motor neurons

Response to stretch….make muscle contract as a protective mechanism

intrafusal fiber

gamma

Where is a Golgi tendon organ? What do they do?

found where muscle converts into a tendon

regulate tension in muscle and tendon…as muscle contracts…this response causes muscles to relax to prevent tendon damage

What would happen during too much muscle tension especially during isometric contractions?

Relaxation reflex by Golgi tendon - protective mechanism

Where are joint receptors found?

Are found in capsules and ligaments around joints

Muscle spindles and Golgi tendon organs are ____ receptors in _____ and _____ junctions

sensory

muscle

musculotendinous

Muscle spindles are found where?

in muscle belly

spindle fibers sense what?

stretch

Golgi tendon organ are wrapped between what in the muscle?

collagen fibers

Muscle spindles monitor _____ and prevent ______? Can be called what 2 types of reflexes?

muscle length

overstretching

Myotatic Reflex or Stretch Reflex

Describe process of muscle spindles? Muscle spindles always maintain what?

extrafusal muscle fibers at resting length...sensory neuron is active and sends input to spinal cord....spinal cord integrates function....alpha motor neurons receive input and give it to extrafusal fibers which then gives it to muscle spindles...causing spppindles to contract due to overstretching

constant state of tension...always firing

overall: muscle stretch-afferent signals to spinal cord-efferent signals to alpha motor neurons-muscle contracts-firing rate of afferent sensory neuron decreases

Describe briefly the process of the Golgi tendon organ?

muscle contracts-neuron fires afferent info to spinal cord which then sends back efferent info to the GTO and then the muscle relaxes and the load is dropped

What do Cutaneous Receptors provide info for? Name 3 kinds?

Pain
Pressure
Temperature

Pacinian Corpuscles, Hair Follicle Receptors and Touch Receptors

Located deep in the skin
Detect deep pressure

Pacinian Corpuscles

Stimulated when hair on the body is deformed or touched

Hair Follicle Receptors

Provide information about the surface of objects

Touch Receptors

What is a feedforward reflex for posture? What about a feedback reflex?

The brain initiates movement and then postural disturbance is anticipated and therefore adjusted right away

Body moves and then posture is disturbed and then feedback for unanticipated postural disturbance fixes the posture

What 2 things improve proprioceptive ability?

Warm-up
Regular activity/exercise

What 3 things decrease proprioceptive ability and explain a little bit why?

Exercise induced muscle fatigue
Injury…can effect nerve endings
Aging…vision declines and nerve endings become damaged

Who had smallest amount of proprioceptive error in a study?

the exercised young

Point about which all particles of the body are evenly distributed

Center of Gravity

COG refers to a _____ direction, why? Another name for COG

vertical

because gravity acts vertically

center of mass

COG is the ______ point of the body? Why?

balancing

Due to the fact that is the point at which the sum of the torques acting on a body equals zero

The location of the center of gravity of any object remains fixed as long as _____?

the body doesn’t change shape

If a body changes shape, center of gravity may _____?

change location

_______ results in changes in the location of the center of gravity

Locomotion

Do males or females have lower COG? why?

Females have lower COG…junk in the trunk..

Center of gravity of humans in a neutral standing posture will vary depending on _____ + ____?

Body build
Height

COG for males? For Females? Why...

______differences, what about shoulder and hips?

More _____ in men
____ fat patterning (men) _____ fat patterning (women)

Males: 55 - 57% of standing height

Females: 53 - 55% of standing height

Average height

Broader shoulders (men) Wider Hips (women)

upper body muscle mass

Android

Gynoid

How does COG vary with age?

as you get older you hinge over and lower COG and moves it forwards…for kids their COG is high because they have big heads

Weebles have very low ____? What does this mean?

COG....objects with low COG are less likely to topple down

General location of center of gravity in human: __________ (during standing posture)?

Upper third of the sacrum

Anything that increases the mass of a body above the original center of gravity will result in ______________? Give an example? This essentially does what? Therefore lowering what increases stability?

the center of gravity shifting upward

Example: extending arms above head or holding a weight above original center of gravity

This decreases stability

Lowering the center of gravity will increase stability

Body characteristics may improve or reduce ________ relative to COG? Give an example?

performance

Boxers and Gymnasts lower their COG

Center of Gravity must be __________ to maintain balance

over the base of support

The part of the body in contact with the supporting surface and the intervening area

Base of Support

What happens when you widen your stance?

Widen the distance between feet, widens the base of support
This improves balance under certain conditions

Feet and all of the _______=base of support

space in between

What can you do to the base of support too enhance stability when external forces are present?

change the shape of the support base

To resist external forces widen the base of support in the direction of ________?

the external force

To resist a force coming from the side, widen stance in the ______ plane? This will make you less stable though if the force comes from _____? Can use a _______ if the direction of the force is not known?

frontal

the front

combination

So long as an object’s ______ falls within its base of support balance can be maintained

line of gravity

The closer the line of gravity to______________ the more stable the object (in the absence of lateral external forces)

the center of the base of support

As the line of gravity approaches the __________ the object becomes less stable? Once it passes this, _____ is lost and a new base of support must be formed

margin of the base of support

stability

We often ________ external loads to make sure the line of gravity remains close to the center of the base of support

counterbalance

When external force is in line with gravity (vertical) we often lean ________ from the force
Example?

away

Carrying a Suitcase and leaning to opposite side

When the external force is lateral we lean _________? Example?

into the force

Leaning into the wind

_____ of a body is only a factor in maintaining balance when motion or an external force is involved

Mass or weight

The amount of force needed to move an object is greater if the ____ is greater

mass

Generally speaking, the greater the mass the greater the _______?

stability

Depending on the condition, ______ may play a role in maintaining balance. Give 2 examples?

friction

Icy pavement
Appropriate footgear

Friction is more of a factor when _____ is involved

motion

When just standing COG points ________ down….as you walk you have a _____ force

vertically

horizontal

If the friction is not sufficient enough to oppose the line of force produced by the body what happens on ice? So what do people do?

the legs will slide out from under the subject causing them to fall

People take short strides on ice to keep vertical force and to not fall

Describe the Romberg Test?

Feet together, arms at side, eyes closed
Loss of proprioception is indicated by a fall to one side

What does BESS stand for? This test utilizes ________? Name them and on what surfaces? Describe what you have to do and how this test works? Results are best utilized if compared to ________?

Balance Error Scoring System

three stances

Double, single, tandem on both firm and foam surfaces

Athletes are instructed to remain motionless with hands on hips for 20 seconds
Unnecessary movements and correction of body position are counted as ‘errors’ (max score = 10)

baseline data

Assessent of balance that quantifies risk for future falls in elderly…uses a scoring sheet

Berg Balance Scale

Best assessment for balance?

BESS

point at which the force vector generated by the weight of an object is applied to the contact surface (ground)

Center of pressure

slight shift in the line of gravity when standing

Postural Sway

Postural Sway results in a change in ____________?

the center of pressure

Postural Sway can be measured in what 2 ways?

Anterior to Posterior or Medial to Lateral

Magnitude of Postural Sway may be impacted by what 7 things?

1. Age…older sway increases
2. Fatigue…exercise or tired from long day
3. Injury…esp. injuries that influence proprioception
4. Bracing
5. Obesity
6. Physiological condition…aka more sway on saturdays
7. Stability of External Environment…ex. On a boat

____ of all Community-dwelling adults experience at least one fall yearly? Falling is the ____cause of death in over 65 age group

1/3

Sixth leading

When there is a balance disruption, what must the body do? What initiates a response first?

Body must be able to determine what strategy to utilize in order to control CoG
Joint mechanoreceptors initiate automatic postural response

Shifts CoG by maintaining feet and rotating body as a rigid mass about the ankle joints

Ankle Strategy for balance disruption

___________ or ________ are responsible for torque production about ankle (muscle)

Gastrocnemius or tibialis anterior

__________ sway is counteracted by gastrocnemius and tibialis anterior?

Anterior/posterior

Effective for slow CoG movements when base of support is firm and within LOS, also effective when CoG is offset from center and is used for minor changes

Ankle Strategy for balance disruption

Relied upon more heavily when somatosensory loss occurs and forward/backward perturbations are imposed

Hip Strategy for balance disruption

Hip strategy aids in control of motion through initiation of _____ and _____ motions at the hip

large

rapid

Effective when COG is near LOS perimeter and when LOS boundaries are contracted by narrower base of support and is used when there is a higher degree
of disruption

Hip Strategy for balance disruption

Utilized when COG is displaced beyond LOS…(line of stability) and a step or stumble is utilized to prevent a fall

Stepping Strategy

Slowest system for balance disruption?

stepping strategy

Muscle Response to Instability Results in a _______ to ______ Activation Pattern?
Gastroc/Soleus time?
Hamstrings time?
Psoas time?

Distal to Proximal

90 – 100 msec…shorter reax time

120- 130 msec

130 – 140 msec…slowest of these three

What is the new trend in exercise science related disciplines?

Functional Movement Assessments

What are some of the most common FM assessments used currently?

FMS
OHS / SLS

What is the foundation that all movement stems from? Its 2 subcategories?

Posture

Static
Dynamic

What is the most common movement pattern used by your clients every day?

Walking

How individuals present themselves in stance

Static Posture

How an individual is able to maintain posture while performing functional tasks

Dynamic Posture

Powerful movements depend on optimal _____alignment and ______?

The spine coordinates whole body power via proper execution of ___________?

A weak foundation leads to ______?

Perfect posture pays dividends by?

spinal... stability

movements or exercises

secondary problems elsewhere in the system

reducing stress/loads

Cervical spine gives ____ freedom of movement

Thoracic allows ____ of your torso

Lumbar spines provides _______

Sacrum provides ________

_________ act as a pivotal axes allowing movement integration between your legs, pelvis and spine.

your head

rotation

stability

the base for your spine to sit on

Sacroiliac joints

Static Postural Assessment is the basis for identifying _____?

muscle imbalances

Regardless of the several factors responsible for changes in joint alignment what still happens which leads to what and causes what?

the body will attempt to still produce the functional outcome desired
Thus the body will make adaptations to accomplish the task at hand
Eventually this can lead to muscle imbalances
With time it can further develop in to tissue damage and pathology

Lack of balance between certain types of muscles

Muscle Imbalance

Certain muscles are prone to _______
Other muscles are prone to _______

Muscle imbalance is often dictated by what?

tightness

weakness

common posture abnormalities

The combination of tightness and inhibition of a muscle can lead to altered ________? It can result in alteration in _______ of joints leading to ______?

movement patterns

biomechanics

degeneration

Muscle Imbalance alters what 3 things?

Alters the Length-Tension relationship of muscles
Alters muscle recruitment patterns
Neural inhibition

Average steps per day?
Average loads each step:
_____ x body weight = ground reaction force when WALKING
____ x body weight = ground reaction forces when RUNNING

5,000-10,000

1-1.5

2 – 3

Look at power, speed, agility, performance, quickness for athlete (above water line)…but now also look at functional movement such as stability mobility and quality of movement (below water line

iceberg effect

The act or power of moving from place to place by means of one’s own mechanisms or power

LOCOMOTION

4 quantitative domains of locomotion?

Temporal

Electromyography

Kinematic (motion description)

Kinetic (causes of motion)

phases (stance/swing) and events (foot-strike, toe-off), stride rate

Temporal domain of locomotion

muscle activation patterns

Electromyography domain of locomotion

stride length, velocity, ranges of motion, acceleration

Kinematic domain of locomotion

ground reaction forces, pressure patterns, joint forces, moments of force, work, energy and power

Kinetic domain of locomotion

Alternating action of the two lower extremities

WALKING

Translatory motion of the body brought about by rotary motion of some of its parts

WALKING

Two Phases of walking?

Swing
Stance/Support

Reference limb in contact with the floor

stance phase

Reference limb not in contact with the floor

swing phase

Two components of Gait? only one foot in contact with the floor?
both feet in contact with floor?

Phase and Support

(1) Single Support:

(2) Double Support:

the stance phase is ___% of the gait cycle?

5 movements of walking?

60%

initial contact, loading response, midstance, late midstance, propulsion

What is one full lower extremity cycle?

One stride

from heel strike to the next heel strike of the same leg

Stride

distance covered in one stride

Stride length

from heel strike of one leg to heel strike of opposite leg

Step

(IFD)...this equals the? What is it? AKA?

Interfoot Distance

walking base

Side-to-side distance between the line of the two feet

Also known as ‘stride width’

Stance vs. Swing:
Stance phase = ____ of gait cycle
Swing phase = ___

Single vs. Double support:
Single support= ___ of gait cycle
Double support= ____

60%

40%

40%

20%

What is the highest point during walking normally? Lowest point?

midstance

double leg support

Name a few things you can analyze during walking?

arms, spine, hips, ankle etc...

During the gait cycle:
The swing of the arms is out of phase with ____?
The shoulders and trunk rotate out of phase with ____ during the gait cycle?
As the upper body moves forward, the ____twists about a vertical axis?
The _______ and the _____ rotate in opposite directions to each other to enhance stability and balance?
Pelvic rotation in ______ plane approx. 8 degree on the swing-phase side?
Also, a slight ______ toward the swing leg?
____ degree dip of the swinging side (i.e. hip adduction)?
The lumbar spine tends to rotate with the ____?

the legs

each other

trunk

thoracic spine

pelvis
horizontal

lateral tilt

5

pelvis

Initial Contact:

Hip has ___ degree flexion

knee has ____ degree flexion

Ankle is?

30

5

neutral

what happens during loading phase to hip knee and ankle?

hip stays at 30 flexion, knee begins at 5 degree flexion then ends at 20 degrees flexion, ankle is neutral to plantar flexion and back to neutral

what happens during mid stance phase to hip knee and ankle?

hip is extending and knee is extending and ankle is dorsiflexed

what happens during terminal phase to hip knee and ankle?

hip is extended beyond neutral

knee is extended and then flexes

ankle dorsiflexes then plantar flexes at end

what happens during pre swing phase to hip knee and ankle?

hip is flexing and then knee is rapid flexing and ankle is rapid plantarflexion

what happens during initial swing phase to hip knee and ankle?

hip is rapid flexion

knee-mostly flexes, then reverses and extends at the end of phase

ankle dorsiflexes

what happens during mid swing phase to hip knee and ankle?

hip flexes

knee has rapid extension

ankle dorsiflexes to neutral

what happens during swing phase to hip knee and ankle?

hip -slight extension

knee- extends throughout but reverses and flexes slightly at end

ankle - remains neutral

mid swing phase

Swing phase

Initial swing phase

Pre swing phase

Terminal phase

Mid stance phase

Loading phase

Initial contact phase

Unnecessary ______ movements decrease gait economy...give three examples?

lateral

a. Excessive trunk rotation
b. Pelvis may drop excessively on one side
c. Pelvic rotation should be just enough to enable the leg to move straight forward

What should you have at the joints during walking? Tendons of two _______ of lower extremity contribute to economy of muscular action in walking

Normal flexibility

joint muscles

Properly functioning _______ contribute to a well coordinated, efficient gait? What can interfere with this?

reflexes

Injury, disease, or substance abuse can interfere with the walking reflex

The swing phase is more ________ than pendular and is longer than ______ phase (for running)

muscular

support

Walking variations up stairs or on a ramp? During the swing phase what is exaggerated?

Forward lean of body to direct the push of legs through the body’s center of gravity

Swing phase is an exaggerated knee lift and dorsiflexion of the ankle

Walking variations down stairs or down a ramp? What is different about the swing phase?

Eccentric contraction of muscles to lower body at a controlled rate, and maintain line of gravity toward the back of the base of support

swing phase has a slight lifting of rear foot to clear the step

2 Differences from walking and running?

there is no double support phase for running and
Running has a flight phase

Two major types of running?

Races
Games and Sports

Concerned with change of direction, pace, and stability (type of running)

Games and Sports

Concerns are time and distance (type of running)

Races

The difference in joint actions between walking and running are a matter of ________ and ________? Essentially the same action, but the _____ is generally larger in running? Differences also exist in __________?

degree and coordination

ROM

Ground Reaction Forces (GRF)

Describe the graph of ground reaction forces for walking vs. running?

vertical force is body weight (y axis) and time is axis. The first peak for running is the heel strike...then the dips indicates the loading response which is an eccentric muscle action. For walking, the heel strike and loading response isn't very noticeable.

The swing phase is more ________ than pendular and is longer than ______ phase

muscular

support

Initial foot contact:
Fast running= ?
Slow running= ?

- ball of foot

- heel or whole foot

During running, the flexed leg brings the mass of the leg ________? What does this reduce and increase?

close to the hip

reducing inertia and increasing angular velocity

Who produces an overall greater force in newtons for ground reaction forces during running? Mid-foot or heel striker?

Heel striker (uses a heel to toe foot pattern)

There are two factors that impact the inertia of a rotating body, what are they?

The mass of the body/object
The distribution of the mass of the body from the axis of rotation

During the support phase in running, the knee and ankle “give” in ____, then _______ as the body passes over the foot?
Support time decrease as ______ increases?
Movements of muscles in spine and pelvis are the same as walking, but more ________ in reaction to leg movements

flexion

extend

speed

vigorous

For running, speed is governed by _______ and _____of stride

length and frequency

determined by length of leg, ROM of hip, and power of leg extensors

Length of Stride

During running, the body becomes a projectile and depends on....
Angle of ______
Speed of ________
Height of ______ at takeoff & landing

take off

projection

center of gravity

determined by speed of contraction and skill of performer

Stride rate

Sprint form of running is usually aimed at what three respective technique variants?

drive, stride and lift

During running this is emphasized during the start and acceleration phases? These 2 are both emphasized during the maximum speed phase?

drive

stride and lift

Starting acceleration and push-off action (first 22-33 yd)

Drive

During the drive of sprinting you want:

_____ thrust with body _____ with a ____ trunk

Horizontal

low

piked

What are 2 techniques to use during a sprint?

Powerful arm action through greater range than stride technique

Full-range driving action with exaggerated knee lift

What does the crouch start enables the runner to do?

exert maximum horizontal force at take off, providing maximum acceleration against inertia

Full-flight striking or pushing action (after 33 yd)

Stride

What type of posture do you want during a stride during a sprint? What type of movement do you want?

“Running Tall” posture, smooth & continuous movement

Forward swing to shoulder height, backward swing to the hip

Full-range arm action

Kick-at-speed pulling action

Lift

What type of posture do you want during lift during a sprint? What do you want in the knees? Arms? What do you want to be light?

running tall posture

Rapid knee lift

Full-range arm action, increased emphasis on rapid pumping or beating

Lighter striking/clawing action

Errors in walking + running can be visible in one location but be caused by ______ in another location? Can they occur in both running and walking?

dysfunction

Yes, one of the 2 or both..depends on person

Trendelenberg gait...this is usually what? If it is bilateral its called what? What are 4 common causes?

Lateral Trunk bending

Usually unilateral
Bilateral = waddling gait
Common causes:
A. Painful hip
B. Hip abductor weakness
C. Leg-length discrepancy
D. Abnormal hip joint

Lateral trunk bending

Overpronation Gait abnormalities can be due to weak _______ muscles? What are some examples? What muscles would be tight? Overpronation could also mean what?

inverter/supination

Tibialis Anterior
Posterior Tibialis
Soleus
Abductor Hallucis

Gastrocnemius
Peroneus Longus
Peroneus Brevis

problems at hip or knee such as knee valgus

Knee valgus could mean what is weak?

Weak gluteus max & medius

COMMON GAIT ABNORMALITIES: Functional Leg-Length Discrepancy....describe what this could be?

Swing leg: longer than stance leg

4 compensations for swing leg being longer than the stance leg?

A. Circumduction…longer leg has to swing around in order to clear it from ground
B. Hip hiking…raise hip to clear long leg from ground
C. Steppage
D. Vaulting- come up on opp. Foot to clear longer leg

Normal walking base in cm? If you have an increased walking base what could be 2 causes? Could also be due to?

5-10 cm

abducted hip or valgus knee

instability

In stance phase (Heel contact – Foot flat)

What happens in the swing phase if your foot isnt dorsiflexed? Could be due to weak ____ or spastic ______?

Foot slap

toe drag

Weak Tibialis Ant.
Spastic plantarflexors

Postural analysis views?

anterior, posterior, lateral and skyline

Posture guidelines for head, shoulders, hips, knees and feet?

head- neutral, ear in line with center of shoulder

shoulders-neutral, center of shoulder should be in line with center of hip

hips-neutral spine with abdominals drawn in

knees-straight

feet- pointing straight with neutral position at ankle

what 2 things should you add in to a picture to evaluate posture?

plumb line and posture grid

good posture: “a state of ______ and _______ balance, which protects the supporting structures of the body against injury or progressive deformity”

“Good posture is present when the ______ passes through the center of each joint just anterior to the midline of the knee, through the greater trochanter, bodies of the lumbar vertebrae, shoulder joint, bodies of the cervical vertebrae, and the lobe of the ear, placing the body in equilibrium and resulting in all internal forces equaling _____” (Kritz & Cronin, 2008)

muscular and skeletal

line of gravity

zero

Name what this is and whats going on with the body? Name some short and tight muscles? Lengthened and weak ones?

Kyphosis-lordosis

forward head, inc cervical lordosis, inc thoracic kyphosis, inc lumbar lordisis, ant. ppelvic tilt

short-neck extensors

lengthened- neck flexors

Name what this is and whats going on with the body? Name some short and tight muscles? Lengthened and weak ones?

Sway back

forward head, inc cervical lordosis, inc thoracic kyphosis, dec lumbar lordosis

short- upper abdominals

lengthened- lower abdominals

Name what this is and whats going on with the body? Name some short and tight muscles? Lengthened and weak ones?

flat back

forward head, inc cervical lordosis, dec thoracic kyphosis, dec lumbar lordosis, post. pelvic tilt

short- neck extensors
lengthened- neck flexors

Name what this is and whats going on with the body? Name some short and tight muscles? Lengthened and weak ones?

Military type

normal cervical spine, normal thoracic kyphosis, inc lumbar lordosis, ant. pelvic tilt

short- lumbar extensors
lengthened- abdominals

Janda’s Compensatory Patterns 3 syndromes?

Upper Cross Syndrome
Lower Cross Syndrome
Pronation Distortion Syndrome

Describe it?

Upper cross syndrome

rounded shoulders

forward head posture

Describe it?

Lower crossed syndrome

Increase lumbar lordosis
Increased anterior pelvic tilt

Results in Rib external rotation
Reduced thoracic mobility (in the transverse plane)
Due to vertebral architecture

Spinal Extension

Pronation Distortion Syndrome

Excessive foot pronation (flat feet)
•Excessive foot external rotation
•Knee flexion
•Knee internal rotation
•Adduction

Pronation Distortion Syndrome

Describe normal Position for scapula ?

Between T2 – T7
3 inches from spine
Rest against rib cage without observable winging

Common Issues to look for in scapula

If your _______ is in a poor resting alignment, your scapulae will never be in the right position.

Winged ***
Protracted/Abducted ***
Retracted/Adducted
Elevated
Visible Muscular differences

thoracic spine

A protrusion of the inferior angle of the scapula
Often accompanied by protracted shoulder girdle

Winged Scapula

Issues associated with winged scapulae:
Because of the forward tilt of the scapula, complete _______ of the shoulder may be restricted?
Weakness of the ________ or _______
Weak Rhomboids and shortened ______?

flexion

serratus anterior or lower traps

Pec Minor

The shoulders are pulled forward

The subscapularis and Pectoralis minor and clavicular & sternal heads of the pectoralis major muscles may be _______
The ______ and _____ may be weak if the medial borders of the scapula also protrude slightly from body.

Protracted Scapula

short

The trapezius (middle fibers) and particularly the rhomboids

Shortened/strong rhomboids – middle trap...where is this seen in?

Retracted Scapula

military stance posture

Upper traps, Levator Scap. are short/tight/active

With this you may see differences where?

Elevated Scapula

left and right sides

What could a trunk tilt crease mean?

one side sags lower

what happens to lumbar spine if pelvis raised on right? on left?

right- flexed to the right and concave to right

left- flexed to left and concave on left

what happens to lumbar muscles if pelvis raised on right? on left?

right- shortened right quadratus lumborum and right lumbar erector spinae

left- shortened left quadratus lumborum and left lumbar erector spinae

what happens to the hip joint if pelvis raised on right? on left?

right- right hip is adducted and left hip is abducted

left- left hip is adducted and right hip is abducted

what happens to the muscles of the hip if pelvis raised on right? on left?

right- shortening of right hip adductors and left hip abductors and imbalance between right and left hamstrings

left- shortening of left hip adductors and right hip abductors and imbalance between right and left hamstrings

How does aging affect posture? inactivity? Poor postural habits? Biomechanical compensation? Body comp? Workplace? Injury?

your body gradually loses its capacity to absorb and transfer forces

leads to loss of natural movement flow,

eventually becomes your structure

muscle imbalance, adaptive shortening, muscle weakness & instability within the “core”,

increases load, stresses on spinal structure, leads to spinal deviation,

curved shoulders

leads to reduced loading capacity or elasticity.

Posture is the single most common cause of painful ______ syndromes affecting the body

soft tissue

tech neck can give you what?

bad posture, curved shoulders

Optimizing muscle balance and posture will help reduce the likelihood of ___________

dysfunction

Joint by joint approach: (stability or mobility?)

foot, ankle, knee, hip, lumbar spine, thoracic spine, scapula, elbow?

stab

mob

stab

mob

stab

mob

stab

stab

mechanisms of locomotion:

at heel strike what is going on with the ankle? During eccentric/loading?

Supinated and locked ankle

Unlocks - moves into pronation (ankle dorsiflexion and rear foot eversion)

What are these things describing?

Impact forces to be attenuated over a longer period
The foot to accommodate uneven surfaces
The foot to roll inward so that the first ray makes contact with the ground in

Essentially this is a _______?

foot pronation

protective mechanism

what happens to ankle during heel lift off?

Move back toward supination to allow toes create rigid lever to propel runner

what are two primary stabilizing muscles of ankle?

They function to:
Minimize ________
Control ________
dynamically support ___________

Tibialis Posterior
Soleus

torsion

rear foot eversion

medial longitudinal arch

3 things that levers Possess?

 Fulcrum/axis
 Resistance Force
 Effort Force

Lever arm consists of?

 Effort arm
 Resistance arm

If the effort & resistance are applied at some other
angle than 90° then the:
 Effort arm is the __________ distance from the
effort line to the fulcrum
 Resistance arm is the perpendicular distance from
the ___________ to the __________

perpendicular

resistance line to the fulcrum

rigid bar that can rotate about a fixed point

Lever

3 things that Levers Possess?

 Fulcrum/axis
 Resistance Force..dumbbell, or gravity, etc
 Effort Force

Bones act as a ______, joints as the _______, muscles as a form of ______, and external forces as the __________? __________ occurs as a result of coordination of levers to produce maximum force?

lever

fulcrum

effort

resistance forces

movement

portion of lever between fulcrum and the force points

Lever arm

distance between fulcrum and pt of effort

 Effort arm

distance between fulcrum and res. Pt.

 Resistance arm

If the effort & resistance are applied at some other angle than 90° then the:
 Effort arm is the _________ distance from the effort line to the fulcrum
 Resistance arm is the perpendicular distance from the resistance line to the ________

perpendicular

fulcrum

Levers serve 2 important functions, what are they? What can both do depending on the type of lever?

1. Overcome a resistance larger than the magnitude of the effort…little effort to overcome a large work load (wheel barrow)…..2. increase the speed and ROM through which a resistance can be moved….both will vary depending on type of lever

ability of a lever to magnify force

 Mechanical Advantage

 Ratio between effort applied to the lever and the resistance overcome by the lever

 Mechanical Advantage

2 equations for mechanical advantage? Explain them both a little

 Mechanical Advantage = R / E (greater the resistance and smaller the effort…the greater the mechanical advantage) or
 Mechanical Advantage = length of force arm/ length of resistance arm

 Levers outside the body

External Levers

External Levers:

 Aid in _________
 Help overcome great _________ with little effort (crowbar)
 Increase ____________ and ________ ...give examples?

daily activities

resistance

range of motion and speed of movement (bat, golf club)

 Levers found within the body

Anatomical Levers

What makes up Anatomical Levers?

bones, joints, and muscles

Muscles can serve as the ___ or ________ force? Going down on a pull up (dealing with levers), the muscles are the _______ force and _____ is the effort force?

effort or resisting force depending on action

resistance force

gravity

________ and _______ of the effort & resisting forces can alter the classification of lever system

Location

source

Typically, in anatomical levers, what is the effort force and resistance force?

 muscle insertion is the effort/force
 Center of Mass is the resistance

Classification of Levers vary in what? Name the 3 types?

arrangement of axis, effort and res. arm

 1. First Class Levers
 2. Second Class Levers
 3. Third Class Levers

 Fulcrum lies between the effort and the resistance…in middle

First Class Levers

2 functions of what lever system?

1. Magnify the effects of the effort

2. Increase speed & ROM

1st class

Examples of what lever system?
 External: seesaw
 Anatomical: Skull tipping forward or back

1st class

going from distance of resistance to axis = ?

res. Arm

distance from effort to axis= ?

effort arm

For 1st class levers, how do we increase mechanical advantage? How do we increase speed and ROM?

greater mechanical advantage if we inc effort arm and dec resistance arm…if we do opposite it will increase speed and ROM

Describe 1st class lever system with a skull? (what is the resistance and effort?)

skull has gravity as resistance and muscles near occipital bone as effort that keep head up

 Resistance lies between the fulcrum & effort

Second Class Levers

For 2nd class levers, the effort Arm is always ______ than the
Resistance Arm? What does this allow for? What is sacrificed?

longer

 Allows for less effort to move a resistance…large mechanical advantage

ROM

2 examples of a 2nd class lever system? Explain what the axis, res. and effort are?

Wheelbarrow or a calf raise…toes=axis, resistance=COG of body, effort= muscle that is shortening and pulling upward

 Effort lies between the axis and the resistance

Third Class Levers

For 3rd class levers, what is the relationship between res. arm and effort arm? What does this mean? What is the advantage? This is the most common what?

 RA is always longer than EA

 Takes more effort to overcome a resistance

 Advantage is increased speed & ROM

anatomical lever

The same system can vary in its _______________ depending on the action of the system and which forces are acting to resist and which are acting as an effort force

classification of the type of lever

lowering the arm is _______ and raising it is __________? Lowering is what type of lever, why? What about when raising, why?

eccentric

concentric

2nd because  Axis = Elbow Joint
 Resistance = Biceps &
Brachialis Muscles
 Effort = Gravity (wt. of arm)...goes axis, res. than effort

3rd class because  Axis = Elbow Joint
 Resistance = Gravity
 Effort = Biceps &
Brachialis muscles...goes axis, effort, then res.

Formula for levers? Need to know ____ of the 4 values? A lever whose EA is longest favors ______?
A lever whose RA is longest favors _____ and ______?

 Effort x Effort Arm = Res. x Res. Arm

just 3

force generation

speed and distance

Levers of the human body typically have longer and short what, why?

 Most have longer RA compared to EA…the EA is short on body because the muscles are close to joint attachment (axis)
 Due to point of muscle attachment

Anatomical levers favor what?

speed and ROM

 Desire Speed & Distance = _______ levers
 Accuracy = _______ levers

Longer

Shorter

Longer levers require more ______ to move them

force

In Lacrosse, a defensive/longer stick does what to the ball? what does it need more of? What does the offensive/shorter stick have?

can throw it further but need more force

higher angular velocity

Longer levers enhance______ and _____?This is detrimental when __________ is needed? Give an example?

linear velocity & ROM

high angular velocity

 Example: Swinging at a fast ball (choke-up to decrease length of bat & increase angular vel.)

Shorter levers may Compromise ______ and ______?

Linear velocity & ROM

A-R-F

F-A-R

A-F-R

2nd class lever

1st class

3rd class

for 1st class levers, do the RA and FA move in the same or opposite directions? 2nd class? 3rd class?

opposite

same

same

Defined as the turning effect produced by a force

Torque

Causes change in angular motion

Torque

Movements of limbs at joints are controlled by torques produced by ___________?

the muscles

Torque produced by a force may be called a _________ or __________?

Moment of Force or Moment

When an external force is directed through the center of gravity of an unrestrained system, it causes that system or object to move in a linear path

Centric Force

When an external force is not directed through the center of gravity of an unrestrained system, it causes that system or object to move in a linear and angular path

Eccentric Force

Forces acting on an object in opposite directions and not directed through the center of gravity...what will the object do? Effects only _____?

Force Couple

object will merely rotate

angular motion of the object

In a force couple, If both forces are equal, then what happens?

the resultant of the two forces is 0, as no change in linear motion occurs

a rotary force

torque

Name a few anatomical force couples?

internal oblique pulling in towards center and external oblique pulling outwards

also, upper trap pulling up and lower trap pulling down

also muscles that cause anterior and posterior pelvic tilt

Rotary force generated by the muscles acting on bone crossing a joint

Internal Torque

There can be muscles acting to cause rotary motion in a given direction and those that resist motion by causing what?
This balance of torque enhances _________?

torque forces in the opposite direction

joint stabilization

Rotary forces generated by external loads acting on the body

External torque

The body works to balance, resist, or overcome external ________?

torques

Name a few different names for internal torque?

moment of effort, effort moment, effort torque

Name a few different names for external torque? Give 2 examples of external torque?

moment of load, resistance torque, resistance moment

gravity

holding a dumbbell

Torque is influenced by the _________ and _______ of the line of action of the force as well as by its _____?

position and orientation

size

Torque is produced by?

magnitude of the force and the distance from the axis of rotation that the force is applied

Torque is a ______ quantity, because the turning effect is around a specific axis that is directed in a specific direction

vector

is a quantity that has both magnitude and direction? Represented by __________?
The magnitude of a vector is its _____?

Vectors

arrow shaped symbols

size

A vector symbol’s orientation on paper represents ______ and its length represents ___________?

direction

magnitude

Counterclockwise Torques are ______
Clockwise Torques are ____________

Positive (+)

Negative (-)

Torques that act about the same axis may be ________ or ____________?

added or subtracted

The distance between the line of action of the force and the axis of rotation is called the ? The greater this distance, the greater the ________ produced by the force

Moment Arm

torque

Can also be referred to as the Force Arm, Lever Arm, or Torque Arm

Moment Arm

the shortest distance from the axis of rotation to the line of action of the force. The shortest distance is always the length of the line that is _________ to the force’s line of action (d⊥)

The force arm

perpendicular ⊥ (90°)

If the system is restricted to moving around an axis, the body rotates when the force is applied but only if the force does not act ______________?

directly through the axis of rotation

The point of application of the force must not be at the _____ and the line of action of the force must not pass ____________?

axis

through the axis

To open (rotate) a door, the force is applied where?

at a point far from the hinges

If the line of force is going directly through the axis of rotation you can’t cause something to rotate…will only push it in what way?

in a linear way

Torque is produced by muscles when they pull on ______? The result is ? The stronger the contraction of a muscle, the greater the ? The longer the force arm, the greater the ?

bones

rotary motion of the body segments

torque on the bone

torque

Just look at picture

look at picture

The greater the _________….the greater the torque
Moment arm doesn’t really change in the human body…in order to inc it what could you do?

moment arm

could recruit more muscles

The point of application of a muscle’s force on a bone (insertion point) cannot be changed, but what can? what is it in line with and how does it change? As a result of the changing direction of muscle force on the bone as the bone rotates, what happens to the force arm? Therefore, the torque that a muscle is able to exert on a bony segment changes as the ______?

the line of action of a muscle’s pull (in line with the direction of the muscle’s shortening)

changes relative to the bone (the angle of muscle’s insertion)

the force arm changes length

segment position changes

Moment arm is biggest at what position on muscles and bone? What does this mean? What happens to it through ROM?

90 (means we can generate the most force here)….will change slightly during a range of motion

Why do you need to keep the dead lift bar close to you?

Bar needs to stay close to you during a dead lift or else if it is far away you will inc torque

The amount of torque acting to rotate a system is found by multiplying the ______ of the applied force by the ____________ from the line of force to the axis of rotation? Units for each?

magnitude

force arm distance

T = Torque
Newton meters
F = Force
Newtons
d⊥ = Length
Meters or feet of the shortest line drawn from the axis to where it meets the line of action of the applied force at 90°

If a force of 50N were applied with a force arm of 2m, the torque produced by that force would be ? If the weight is lighter, what happens? Show this? If the weight is placed closer to the axis what happens? (same original force) Show this?

100 N-m, or 100 torque units

it creates less torque
25 N * 2 m = 50 Nm

it creates less torque
50 N * 1 m = 50 N

If the line of force of the weight is directed through the axis itself, what happens?

zero distance (d⊥) results, therefore zero torque and no rotation is produced.
100 N * 0 m = 0 units of torque (no rotation)

Determine the Torque given the following: 400 N and 4 m?

1600 N-m

what is the unknown force?

FA = 15cm

RA = 5cm

R = 400

Set them equal to each other

400 x 00.5= 20 Nm

20 Nm= _____ x o.15

Force= 133

RA = 20cm R = 2000 N
FA = 5cm F = ?

2000 x .2= ______ x .5
400 Nm= ______ x 0.5
Force= 8000 N

RA = 15cm R = 2000 N
FA = 25cm F = ?

2000 x .15= ____ x .25
Force= 1200 Nm

Often, we purposely increase __________ in order to increase torque so that we can more easily move a relatively large resistance (increasing our leverage)

force arm length

distance between the axis and the point of resistance application

Resistance arm

There is a _______ relationship between length of the two lever arms. Give examples?

Inverse

Between force & force arm
Between resistance & resistance arm

The longer the force arm, the _____ force required to move the lever if the resistance & resistance arm remain constant. Shortening the resistance arm allows a ______ resistance to be moved if force & force arm remain constant

less

greater

__________ relationship between force components & resistance components. If either of the resistance components increase, what would happen?

Proportional

there must be an increase in one or both of force components

Greater resistance or resistance arm requires what? Greater force or force arm allows for what?

greater force or longer force arm

a greater amount of resistance to be moved or a longer resistance arm to be used

Human leverage system is built for _________ and ________ at expense of force?

speed & range of movement

Short force arms & long resistance arms require great _______ to produce movement?

muscular strength

Human leverage for sport skills requires several _______? Give an example?

levers

throwing a ball involves levers at shoulder, elbow, & wrist joints

The longer the lever, the more effective it is in imparting ______? Give an example?

velocity

A tennis player can hit a tennis ball harder with a straight-arm drive than with a bent elbow because the lever (including the racket) is longer & moves at a faster speed

Long levers produce more _________ and thus better performance in some sports such as baseball, hockey, golf, field hockey, etc. Explain the 2 points in the picture?

linear force

First point doesn’t move as far…distance gets greater as you move away from axis of rotation…means that 2nd point is moving faster because it gets further in the same amount of time

For quickness, it is desirable to have a short _________? Describe this with a baseball catcher throwing on the field? What does this increase?

lever arm

baseball catcher brings his hand back to his ear to secure a quick throw…inc angular velocity

Tension in the muscles crossing a joint does not always promote what?

the joint’s stability

Only the component of muscle force acting ____________ to the long axis of the attached bone actually contributes to the rotation of a body segment around the joint crossed by the muscle

perpendicular

There exists both _________ and ________ forces created by muscle activation

linear (non-rotary) and torque (rotary)

The angle of pull of most muscles in the resting position is ?

less than 90 degrees

Less than 90 degrees (angle that we start off in pulling), nonrotary component force is directed ______ joint. Name of force?

toward

(compressive or stabilizing force)

If angle of pull exceeds 90 degrees then the nonrotary component force is directed ______ from the joint. Name of force?

away

(distensive or dislocating force)

When you think about human movement and muscle attachments it is rare that the angle of pull is ? Thus – typically the muscle is generating either a ______ or _____ force in addition to rotary force

at 90 degrees. When it is, it is for a brief moment

stabilizing or distensive

name each picture

1st= stabilizing force

2nd= right at 90

3rd= dislocating force

Because we want to maximize the application of force to generate rotary motion we rely on the body’s structure to increase our ____________? Name one way we do this?

mechanical advantage

One way we do this is through the utilization of pulleys

changes the direction of the force, making it easier to lift things

A pulley

When the direction of pull of a muscle is altered, the bone or bony prominence causing the deflection

Anatomical Pulleys

The function of any pulley is to? What is this in humans?

redirect a force to make a task easier.

The “task” in human movement is to rotate a body segment.

Anatomic pulleys (in the majority of instances) make this task easier by deflecting the action line of the muscle _____ from the joint axis, thus increasing the ____________. By increasing this, a force of the same magnitude (with no extra energy expenditure) produces greater _____?

away

MA of the muscle force

torque

describe pulleys with tendons?

Tendons wrap around certain bones to essentially create a pulley and inc moment arm length

Act to increase the angle of pull so that it increases the rotary component of force. What does this also increase and allow for? an example of this on the body?

Anatomical Pulley

It increases the moment arm which allows for more force to be generated

patella

Rotation =?
Non-Rotation =?

- Torque

– Linear motion

Rotational Component of Magnitude formula? What does this tell us and not tell us?

Fp (original force) = Fm (sin α) (sin of angle of pull)

This only tells us what portion of the force is generating rotary motion
It does not tell us the actual torque

Non-Rotational Component of Magnitude formula?

Fp (proportion of original force) = Fm (force mag) (cosα)

Do we do sin or cos if angle is at 90, why?

For linear movement
Don’t have to do sin or cos if angle is at 90 degrees
Cos(90)=0 and sin(90)=1…….no linear movement only rotation

How much torque is produced at the elbow by the biceps brachii inserting at an angle of 60° on the radius when the tension in the muscle is 400 N?
Assume that the muscle attachment to the radius is 3 cm from the center of rotation at the elbow joint.

Fp = Fm (sin α)
Fp = (400 N)(sin 60°)
Fp = 346.4 N
Tm = (Fp)(d⊥)
Tm = (346.4 N)(0.03 m)
Tm = 10.4 N-m

what do you assume if they give you no angle to the rotational component? What if they give you an angle?

If no angle is given to effect the rotational component of a force magnitude then that force magnitude is the rotational component and thereby the overall Force

(Force Magnitude) x (sin α) = Rotational Component

How much force must be produced by the biceps brachii attaching at 90° to the radius at 3 cm from the center of rotation at the elbow joint, to support a weight of 70 N held in the hand at a distance of 30 cm from the elbow joint?
neglect the weight of the forearm and the hand, and neglect any action of other muscles

Since sin 90° = 1 it is not a factor in these calculations

Convert centimeters to meters by dividing by 100
(FM )( MM) = (FR )( MR)
(FM)(.03 m) = (70 N)(.30 m)
(FM)(.03 m) = (21 N-m)
FM = 21 N-m ÷ .03 m
FM = 700 N

The quadriceps tendon attaches to the tibia at a 30° angle 4 cm from the joint center at the knee. When an 80 N weight is attached to the ankle 28 cm from the knee joint, how much force is required of the quadriceps to maintain the leg in a horizontal position?

ankle force= Its negative because its clockwise which is negative (at ankle…force going down)
Counterclockwise= positive (force pointing up)

sin(30) x original force= new force

0.04 m=distance

80 x 0.28=torque....= 22.4

22.4= force x 0.04

force=560

sin(30) x original force= 560

original force = 1120 N

Use Non-Rotational Components to determine what? Name 2 types and if they are positive or negative?

Joint Reaction: Distensive or Compressive

Reminder: we will record Compressive forces as (-) and Distensive forces as (+)

The biceps brachii on the lower arm during an isometric contraction while holding a 70 N dumbbell.
Determine the muscular effort required to hold the segment and object in this position and the joint reaction force caused by the translational effects of the forces applied.

LOOK AT PIC ON PHONE

Sum compressive forces (neg) and determine the resulting distensive forces for joint to be stable

Cos=non rotational component…has nothing to do with torque piece

do that at very end

F=1496 and distensive forces= 16.5

What do you do with 2 forces acting against the muscular force ?

…add them together

Distensive = what angle?

Stabilizing= ?

Greater than 90

less than 90

In this image, do the lengths of the resistance arm and effort arm change?

What type of lever is this?

yes

Third class…most concentric actions
are this

If the point of muscle attachment is 2cm from the elbow joint, and the 44N dumbbell is 20 cm from the elbow how much muscle force must be developed to raise the dumbbell?

440 N +

How does arm length impact this?
What about body mass/size?

The body weight increases the amount of resistance force
Longer their arms…greater the moment arm length which increases torque

Application to Sports

When you desire_______ on a ball you apply an ______ force (torque)

rotation (spin)

eccentric

Describe how this picture is beneficial?

Increases moment arm which increases torque because its farther away from their pivot point…start low and hit high

Power output relative to crank length?

What happens if crank length gets too large?

As crank length gets larger….larger moment arm which increases power output
As we get too large though power goes down because muscles come up to close to your body when you pedal and effect length tension relationship

Understanding torque is important for having a better knowledge about the mechanics of various __________?

exercises

How to compare exercises
Safety of exercises
Impact of body segment differences during certain exercises

Torque and Exercise

When is external torque greatest during deadlifting? Why?

1……barbell is furthest from hips here which increases moment arm length

During a Deadlift
The lifter with the longer _____ will have a larger external moment arm .... Thus will have to produce more _____ to overcome the same load.
The lifter with longer _____ will have an advantage
The ____ position for the deadlift is dependent on arm length

A lifter with longer arms will have a greater _______ than a lifter with short arms.

Describe how lifters with shorter arms struggle?

femur

force

arm length

initial

mechanical advantage

The lifter with short arms must drop their hips lower, increasing the external moment arm and thus a greater torque must be generated to lift the bar.

what does this do to the back?

This hip extension puts a lot of external load on the back

Front vs Back Squat

Assuming the load is the same, in which position is torque produced by the bar greatest on the low back?
Look at moment arm length differences

Last pic has greatest external torque bc you lean forward the most with back squatting which increases moment arm length

What type of lever is this?
How can you modify a push-up to reduce torque?

Pivot at feet, resistance in middle and force up above
2nd class
Put knees to the ground to shorten the effort arm

Weight force = 25 N
Weight angle = 120
Weight distance = 16 cm
Axis force = 10 N
Axis distance = 8 cm
Axis angle = 120
Muscle force = ?
Muscle Angle = 25
Muscle distance = 4 cm

-3.46 torque res
-0.69 torque axis…….. -4.15 total torque
+4.15 M torque

Muscle force= 103.75 (4.15= force x 0.04)
Original force= 245.5 (original force= 103.75/sin25)
Cos part……
+12.5 comp.
+5 comp.
-222.5 dist. (cos25 x 103.75) = 204.99

just have one be positive and the other negative...as long as they oppose each other i pointing inn different directions