Balance and stability are used ______?
Resistance to disruption of equilibrium
A persons ability to control equilibrium
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
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?
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 _____?
Object’s center of gravity does not change when the object’s position changes? Give an example?
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
Base of support
Mass of the body
External Factors- Environmental Conditions
Proprioception is a term coined in ____?
The ability to sense where our body is in space? Its a sense of ____ and _____? It is described to be _____?
Sense of position & balance
Kinesthesia is a term coined in _____? “kenein” =
“aesthesis” = _____?
Movement of body
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?
Close eyes and touch nose example…we know general location of space
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
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
Name 4 types of Mechanoreceptors?
Skeletal Muscle & Joint Receptors
Cutaneous & Fascial Receptors w/in skin
Proprioception also obtains information from what 2 things?
Sensory input received from mechanoreceptors are integrated and appreciated at what three levels of the CNS?
Higher levels such as cerebral cortex + cerebellum
Can provide direct motor responses in the form of reflexes…reflex reaction
Integration of ______ information with visual and vestibular inputs to aid in control of typical ______ patterns, continual output to maintain _____ + _____
balance & posture
Conscious awareness of movements – voluntary movements
Higher levels (cerebral cortex & cerebellum)
Muscle spindle provide______ at all times? Why is this special?
(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
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
Muscle spindles are found where?
in muscle belly
spindle fibers sense what?
Golgi tendon organ are wrapped between what in the muscle?
Muscle spindles monitor _____ and prevent ______? Can be called what 2 types of reflexes?
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?
Pacinian Corpuscles, Hair Follicle Receptors and Touch Receptors
Located deep in the skin
Detect deep pressure
Stimulated when hair on the body is deformed or touched
Hair Follicle Receptors
Provide information about the surface of objects
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?
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
because gravity acts vertically
center of mass
COG is the ______ point of the body? Why?
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 _____?
_______ results in changes in the location of the center of gravity
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 _____ + ____?
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
Broader shoulders (men) Wider Hips (women)
upper body muscle mass
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?
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?
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
We often ________ external loads to make sure the line of gravity remains close to the center of the base of support
When external force is in line with gravity (vertical) we often lean
________ from the force
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
Generally speaking, the greater the mass the greater the _______?
Depending on the condition, ______ may play a role in maintaining balance. Give 2 examples?
Friction is more of a factor when _____ is involved
When just standing COG points ________ down….as you walk you have a _____ force
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
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)
Assessent of balance that quantifies risk for future falls in elderly…uses a scoring sheet
Berg Balance Scale
Best assessment for balance?
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 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
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
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
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?
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
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
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
Slowest system for balance disruption?
Muscle Response to Instability Results in a _______ to ______
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?
OHS / SLS
What is the foundation that all movement stems from? Its 2 subcategories?
What is the most common movement pattern used by your clients every day?
How individuals present themselves in stance
How an individual is able to maintain posture while performing functional tasks
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?
movements or exercises
secondary problems elsewhere in the system
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.
the base for your spine to sit on
Static Postural Assessment is the basis for identifying _____?
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
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
Certain muscles are prone to _______
Other muscles are prone to _______
Muscle imbalance is often dictated by what?
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 ______?
Muscle Imbalance alters what 3 things?
Alters the Length-Tension relationship of muscles
Alters muscle recruitment patterns
Average steps per day?
Average loads each step:
_____ x body weight = ground reaction force when WALKING
____ x body weight = ground reaction forces when RUNNING
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
The act or power of moving from place to place by means of one’s own mechanisms or power
4 quantitative domains of locomotion?
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
Translatory motion of the body brought about by rotary motion of some of its parts
Two Phases of walking?
Reference limb in contact with the floor
Reference limb not in contact with the floor
Two components of Gait? only one foot in contact with the
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?
initial contact, loading response, midstance, late midstance, propulsion
What is one full lower extremity cycle?
from heel strike to the next heel strike of the same leg
distance covered in one stride
from heel strike of one leg to heel strike of opposite leg
(IFD)...this equals the? What is it? AKA?
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= ____
What is the highest point during walking normally? Lowest point?
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 ____?
Hip has ___ degree flexion
knee has ____ degree flexion
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
what happens during mid swing phase to hip knee and ankle?
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
Initial swing phase
Pre swing phase
Mid stance phase
Initial contact phase
Unnecessary ______ movements decrease gait economy...give three examples?
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
Properly functioning _______ contribute to a well coordinated, efficient gait? What can interfere with this?
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)
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?
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)
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
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
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
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
Angle of ______
Speed of ________
Height of ______ at takeoff & landing
center of gravity
determined by speed of contraction and skill of performer
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?
stride and lift
Starting acceleration and push-off action (first 22-33 yd)
During the drive of sprinting you want:
_____ thrust with body _____ with a ____ trunk
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)
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
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?
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
Bilateral = waddling gait
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?
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
B. Hip hiking…raise hip to clear long leg from ground
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?
abducted hip or valgus knee
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 ______?
Weak Tibialis Ant.
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
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
Name what this is and whats going on with the body? Name some short and tight muscles? Lengthened and weak ones?
forward head, inc cervical lordosis, inc thoracic kyphosis, inc lumbar lordisis, ant. ppelvic tilt
lengthened- neck flexors
Name what this is and whats going on with the body? Name some short and tight muscles? Lengthened and weak ones?
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?
forward head, inc cervical lordosis, dec thoracic kyphosis, dec lumbar lordosis, post. pelvic tilt
short- neck extensors
lengthened- neck flexors
normal cervical spine, normal thoracic kyphosis, inc lumbar lordosis, ant. pelvic tilt
short- lumbar extensors
Janda’s Compensatory Patterns 3 syndromes?
Upper Cross Syndrome
Lower Cross Syndrome
Pronation Distortion Syndrome
Upper cross syndrome
forward head posture
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
Pronation Distortion Syndrome
Excessive foot pronation (flat feet)
•Excessive foot external rotation
•Knee internal rotation
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.
Visible Muscular differences
A protrusion of the inferior angle of the scapula
Often accompanied by protracted shoulder girdle
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 ______?
serratus anterior or lower traps
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.
The trapezius (middle fibers) and particularly the rhomboids
Shortened/strong rhomboids – middle trap...where is this seen in?
military stance posture
Upper traps, Levator Scap. are short/tight/active
With this you may see differences where?
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,
leads to reduced loading capacity or elasticity.
Posture is the single most common cause of painful ______ syndromes affecting the body
tech neck can give you what?
bad posture, curved shoulders
Optimizing muscle balance and posture will help reduce the likelihood of ___________
Joint by joint approach: (stability or mobility?)
foot, ankle, knee, hip, lumbar spine, thoracic spine, scapula, elbow?
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 _______?
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:
dynamically support ___________
rear foot eversion
medial longitudinal arch
3 things that levers Possess?
Lever arm consists of?
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 __________
resistance line to the fulcrum
rigid bar that can rotate about a fixed point
3 things that Levers Possess?
Resistance Force..dumbbell, or gravity, etc
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?
portion of lever between fulcrum and the force points
distance between fulcrum and pt of effort
distance between fulcrum and res. Pt.
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 ________
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
Ratio between effort applied to the lever and the resistance overcome by the lever
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
Aid in _________
Help overcome great _________ with little effort (crowbar)
Increase ____________ and ________ ...give examples?
range of motion and speed of movement (bat, golf club)
Levers found within the body
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
________ and _______ of the effort & resisting forces can alter the classification of lever system
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
Examples of what lever system?
Anatomical: Skull tipping forward or back
going from distance of resistance to axis = ?
distance from effort to axis= ?
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?
Allows for less effort to move a resistance…large mechanical advantage
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
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?
2nd because Axis = Elbow Joint
Resistance = Biceps &
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
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 levers require more ______ to move them
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
2nd class lever
for 1st class levers, do the RA and FA move in the same or opposite directions? 2nd class? 3rd class?
Defined as the turning effect produced by a force
Causes change in angular motion
Movements of limbs at joints are controlled by torques produced by ___________?
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
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
Forces acting on an object in opposite directions and not directed through the center of gravity...what will the object do? Effects only _____?
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
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
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
Rotary forces generated by external loads acting on the body
The body works to balance, resist, or overcome external ________?
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
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
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
is a quantity that has both magnitude and direction? Represented by
The magnitude of a vector is its _____?
arrow shaped symbols
A vector symbol’s orientation on paper represents ______ and its length represents ___________?
Counterclockwise Torques are ______
Clockwise Torques are ____________
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
Can also be referred to as the Force Arm, Lever Arm, or Torque 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 ____________?
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 ?
rotary motion of the body segments
torque on the bone
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?
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?
force arm distance
T = Torque
F = Force
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
100 N * 0 m = 0 units of torque (no rotation)
Determine the Torque given the following: 400 N and 4 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
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
There is a _______ relationship between length of the two lever arms. Give examples?
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
__________ relationship between force components & resistance components. If either of the resistance components increase, what would happen?
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?
Human leverage for sport skills requires several _______? Give an example?
throwing a ball involves levers at shoulder, elbow, & wrist joints
The longer the lever, the more effective it is in imparting ______? Give an example?
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?
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?
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
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?
(compressive or stabilizing force)
If angle of pull exceeds 90 degrees then the nonrotary component force is directed ______ from the joint. Name of force?
(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?
One way we do this is through the utilization of pulleys
changes the direction of the force, making it easier to lift things
When the direction of pull of a muscle is altered, the bone or bony prominence causing the deflection
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 _____?
MA of the muscle force
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?
It increases the moment arm which allows for more force to be generated
– 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
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
80 x 0.28=torque....= 22.4
22.4= force x 0.04
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?
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?
Third class…most concentric actions
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)
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
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 __________?
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?
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
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)
-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