PowerPoint Chapter 11 Flashcards
Bone is ____ ____
Continually ____ and ____
The ____ ____ for the body
Is a system of ____ allowing movement to be possible?
Bone is living tissue
Continually modeled and remodeled
The skeletal framework for the body
Is a system of levers allowing movement to be possible
What are 3 things to remember about the structure and make up of bones?
Strong
Light weight
Organized
What are the four components of bone?
Calcium Carbonate
Calcium Phosphate
Collagen
Water
____ ____ and ____ ____ make up 60-70% dry weight, stiffness & compressive strength?
Calcium carbonate
Calcium phosphate
____ and ____ make up 30-40% bone weight, Strength and flexibility?
Collagen
Water
What provides flexibility to bone?
Collagen
What provides strength to bone and is helpful in the transportation of minerals?
Water
What other minerals are bones made of and what do they do?
Minerals – Magnesium, Sodium, Fluoride
Influence structure & metabolism during growth & development
What is stiffness in bones and where does it come from?
Stiffness – comes from calcium in the boney tissue
Defined as: A ratio of stress to strain in a loaded material
(Stress/relative change in shape)
What is compressive strength in bones?
Compressive strength – (Calcium deposits benefit as well)
The ability to resist pressing or squeezing forces
What does tensile strength do in bones and what is it the result of?
Tensile strength – a result of Collagen
The ability to resist pulling or stretching forces
How is bone classified?
Bone classification is based on Porosity
(Amount of pores or cavities located in the bones structure)
(As age increases; often porosity of bone increases)
____ ____ bone tissue is called ____ bone: 50-90% porosity?
High Porous bone tissue is called Trabecular bone: 50-90% porosity
What is another name for Spongy bone?
Trabecular bone
Describe Spongy bone?
Less compact mineralized connective tissue. Typically found at the end of long bones and vertebrae (Spongey bone)
30 to +90% tissue volume made up of non-mineralized tissue
Noted for its honeycomb like structure and aka spongy bone
____ ____ bone tissue is ____bone : 5-10% porosity?
Low porous bone tissue is Cortical bone : 5-10% porosity
What is another name for compact bone?
Cortical bone
Describe cortical bone?
Low porous bone tissue is Cortical bone : 5-10% porosity
More compact mineralization (5-30% non mineralized tissue)
Found as part of the shaft of long bones. (Compact bone)
Not all bones have the same ____ of cortical and trabecular bone?
____ bones. All different and all created with a purpose of structure?
Not all bones have the same allotments of cortical and trabecular bone.
206 bones. All different and all created with a purpose of structure.
Cortical bone is ____ than trabecular bone, it can withstand greater stress but ____ ____?
Cortical bone is stiffer than trabecular bone, it can withstand greater stress but less strain
Spongy Bone Appears like a ____, slivers of bone connecting in a ____.
Spaces are filled with ____ ____ ____. Few osteons and no central canals.
Provides ____ with very little ____.
Spongy Bone Appears like a sponge, slivers of bone connecting in a matrix.
Spaces are filled with red bone marrow. Few osteons and no central canals.
Provides strength with very little mass.
4 types of bones + examples?
Short bones – carpals, tarsals
Flat bones – scapula, sternum, ribs, patella
Irregular bones – vertebrae, sphenoid
Long bones – Humerus, Femur
What is articular cartilage?
Articular cartilage – firm thick covering of long bones.
What are the two kinds of bone growth?
Longitudinal
Circumferential
Longitudinal growth happens at the ____ ____
Open until age of ____.
Some men, few women, keep growing until age ____?
Longitudinal growth happens at the epiphyseal plate
Open until age of 18.
Some men, few women, keep growing until age 25
When does circumferential growth occur and what is it?
Circumferential growth occurs throughout your whole life
Diameter growth of the internal layers of the periosteum.
What are osteoblasts?
Builders
What are osteoclasts?
Reabsorb
As we age we fight the progressive loss of ____ in our bones?
Making bones more ____?
As we age we fight the progressive loss of collagen in our bones
Making bones more brittle
Bone mineral density occurs mainly in ____ -____/____ years of age?
Peak happening at different times for ____ and ____?
Bone mineral density occurs mainly in 6 -12/14 years of age
Peak happening at different times for men and women
Women have more tendency for bone density loss due to ____?
Seen in both ____ and ____ bone?
Women have more tendency for bone density loss due to Menopause
Seen in both cortical and trabecular bone
What is Wolff’s law?
Wolff’s law
“Bone strength increases and decreases as the functional forces on the bone increase and decrease”
My version – “Bone adapts to the forces placed upon it.”
What is remodeling?
Remodeling of a bone is really the reabsorption of fatigue-damaged old bone which is replaced with new bone
What is bone remodeling the result of?
A result of a dynamic mechanical load on the bone causing deformation or strain
What is bone modeling?
Bone modeling is the forming of new bone
Not because of damage. Often to mature a bone
What is the process of remodeling bone (2)?
Bone receives a Bending load (Aka Bone is strained)
Lays down new bone to support strain while old bone is reabsorbed and remodeled
Stress fracture has a bone callus = ____ ____ ____
Stress fracture has a bone callus = sign of healing
Large and frequent strains = ____ in bone mass
Large and frequent strains = ↑ in bone mass
Osteocytes are sensitive to changes in flow of ____ ____ from strains?
Osteocytes are sensitive to changes in flow of interstitial fluid from strains
Remodeling is a balance of ____ and ____?
Remodeling is a balance of osteoblasts and osteroclasts
____% of Trabecular bone is remolded each year
25% of Trabecular bone is remolded each year
What are four keys that cannot be replaced for healthy bones?
Healthy diet
Lean body mass
Strength
Regular physical activity
____ ____ is the most consistent stress to the body?
____ people usually have bigger bones?
Body weight is the most consistent stress to the body
Heavier people usually have bigger bones
What is bone hypertrophy and what factors influence it?
Increase in bone mass due to DOMINATING Osteoblast activity
Occupation, activity levels, childhood activity levels, and correlated stress to area
How do high, low, and non impact sport affect bone composition respectively?
High impact sports – LOTS of Jumping – all display higher avg bone density and bone shape modeling respective to sport
(Gymnastics, VB, Martial arts, Football, High Jump?)
Lower impact sports – LOTS of Running – display bone modeling but no increase to bone density
(Basketball, XCC)
Non impact sports – NO improvement to bone composition
(Swimming, cycling)
What is bone atrophy?
Decrease in bone mass resulting from predominate of osteoclast activity
Why would bone atrophy happen?
All due to reduced mechanical stress
(Example – Astronaut in space, Sedentary senior, bedridden patient)
Weakened bone = more potential for ____ (trabecular)?
Weakened bone = more potential for fracture (trabecular)
Astronaut loses ____-____% bone mass in ____ month in space = same # postmenopausal women lose in 1 year?
Astronaut loses 1-3% bone mass in 1 month in space = same # postmenopausal women lose in 1 year
What is osteoporosis?
Disorder involving decreased bone mass and strength with one or more resulting fractures
What is osteopenia?
Osteopenia – condition of reduced bone mineral density that predisposes the individual to fractures
In 2010 Reported ____ Americans were being treated for Osteoporosis
(____M fractures/year
Costing $____Billion per year to treat)
In 2010 Reported 10M Americans were being treated for Osteoporosis
2M fractures/year
Costing $19Billion per year to treat
Osteoporosis is seen in elderly, ____ of all women and ____ of men?
Osteoporosis is seen in elderly, 1/2 of all women /and 1/3rd of men
Risk factor list for osteoporosis (5)?
Risk factor list: Female, White or Asian ethnicity, older age, small stature/frame size, family history of Osteoporosis
(Female athlete triad)
Common sites of osteoporotic fractures?
Common sites for osteoporotic fractures: Radius, Ulna, Femoral Neck, Spine
What makes Osteoporosis so hard to treat??
It is not a ____
Not a result of ____
It is a culmination of a life of ____ and ____
What makes Osteoporosis so hard to treat??
It is not a disease
Not a result of aging
It is a culmination of a life of habits and choices
What life habits and choices impact osteoporosis (4)?
Poor diet, inactive lifestyle, hormone level issues, posture.
Single Best preventative treatment for osteoporosis…… PEAK Bone Mass during Childhood and adolescence. Get your Kids ____!!!
Proper ____consumption
____ ____ helps the body absorb calcium
Single Best preventative treatment for osteoporosis…… PEAK Bone Mass during Childhood and adolescence. Get your Kids Moving!!!
Proper Calcium consumption
Vitamin D helps the body absorb calcium
What is a fracture?
Fracture – disruption in the continuity of a bone
What are the 7 types of fractures?
Green stick
Fissured
Comminuted
Transverse
Oblique
Spiral
Stress
What is a salter harris fracture?
Fracture to the epiphyseal plate classified on how it goes through the plate
What are the three general types of joints?
Immovable
Slightly movable
Freely movable
What are the types of immovable joints?
Sutures
Syndesmoses
What are the two types of slightly movable joints?
Synchondroses
Symphysis
What are the six types of freely movable joints?
Pivot
Ball and socket
Hinge
Gliding
Saddle
Condyloid
Nonaxial, Uniaxial, Biaxial, Triaxial
1 deg of Freedom… etc
Joints often associated with ____ and ____ sheaths?
Nonaxial, Uniaxial, Biaxial, Triaxial
1 deg of Freedom… etc
Joints often associated with Bursae and tendon sheaths
What are bursae and what are they helpful in?
Bursae- small capsules, lined with synovial membranes and filled with synovial fluid. Designed to cushion structures.
Most helpful at separating bone and tendons
What is a tendon sheath?
Tendon Sheath – double layered synovial structures surrounding tendons in close proximity to bones.
Describe articular cartilage?
Protective layer at the end of bones
-1-5mm thick
-Provides lubrication to joint
-Disperses compressive forces across surface of bones in contact
-Decreases friction between bones during articulation
-Gained during growing years.
More activity = better results
-Little healing can occur after injury
Describe articular fibrocartilage?
Soft- tissue discs or menisci that intervene between articulating bones
(Meniscus, Vertebral Discs, TFCC)
Roles and responsibilities
-Distribute loads over joint surface and situation of structures
-Limit slippage of one bone on the other
-Protect peripheral articulation
-Retention of joint lubrication
-Shock absorption
Describe articular connective tissue?
-Tendons and ligaments have slightly extensible abilities.
-Passive tissues composed of collagen and elastic fibers
-Response to mechanical stress is to beef up (hypertrophy) or thin out when under used (atrophy)
-Heal nicely if damaged.
-Tendon used most often to repair ligamentous injuries like the ACL and UCL
Joint stability is factors assisting a joints ability to ____ abnormal displacements of articulating bones?
Joint stability is factors assisting a joints ability to resist abnormal displacements of articulating bones
What three things that influence joint stability?
Joint shape
Arrangement of ligaments and muscles
Connective tissues
How does joint shape affect joint stability (ball and socket)?
-Articulating ends of the joint are often opposites.
-Ex. Ball and socket. (concave and Convex surfaces)
-Requires a Closed packed position for stability
-Loose packed position for flexibility
How does the arrangement of ligaments and muscles affect joint stability?
Angle of attachments are arranged so that when a muscle exerts tension, the articulating ends of the bones at the joint crossed are pulled closer together, enhancing joint stability.
Strong Ligaments, load capacity of 112lbs, and muscles increase stability
Tendons have an Ultimate Strength is 14,500 lbs/in2 connecting muscle to bone
Strong Ligaments, load capacity of ____, and muscles increase stability?
Strong Ligaments, load capacity of 112lbs, and muscles increase stability
Tendons have an Ultimate Strength is ____ lbs/in2 connecting muscle to bone?
Tendons have an Ultimate Strength is 14,500 lbs/in2 connecting muscle to bone
How does connective tissue affect joint stability?
Fascia (Fibrous white connective tissue) that surrounds muscles provides support and protection
Although can also cause adhesions (False sense of stability in a joint)
What are the three abilities of fascia?
Stretch (elasticity)
Slide (spreading)
Divide (split and rejoin)
What are the two types of range of motion?
Static
Dynamic
Joint flexibility is often relative to genetic laxity of ____ ____ and ____ crossing joints?
Joint flexibility is often relative to genetic laxity of collagen tissues and muscles crossing joints
____ flexibility significantly increases chance of injury?
Can lead to muscle ____, and tendon ____?
Limited flexibility significantly increases chance of injury.
Can lead to muscle tearing, and tendon rupture
____ flexibility also can lead to injury with a lack of stability?
Such as ____ or ____ or ___ ___?
Excessive flexibility also can lead to injury with a lack of stability
Subluxation or dislocation or ligamentous injuries
What are the two things involved in the neuromuscular system during stretching?
Golgi tendon organ
Muscle spindles
Describe the golgi tendon organ?
Found at the musculotendinous junction
Sensory receptor inhibiting tension development in a muscle. Instead, initiating tension development in antagonist muscles
Works with active or passive tension
Describe muscle spindles?
Named for its shape, located parallel to muscle fibers in bundles of 3-10.
Sensitive to the amount of lengthening a muscle experiences statically and the rate at which muscle will lengthen dynamically
Sensory receptors provoking reflex contraction in a stretched muscle and inhibiting tension development in antagonist muscles
What two things do muscle spindles do?
Stretch reflex
-“Reflex” or immediate firing of a muscle due to a stimulation of the muscle spindles
Reciprocal inhibition
-Inhibition of tension development in the antagonist muscles resulting form activation of muscle spindles
What are the five components of the hip joint?
Transverse acetabular ligament
Labrum
Acetabulum
Femoral neck
Femoral head
Describe the femoral head?
2/3rds a sphere covered by Articular Cartilage
Greatest load in the superior quadrant
Describe the femoral neck?
Frontal plane shows Angle of inclination
Neck to shaft angle
Normal is 125֯, Range of 90-135֯
Transverse plane showing Angle of Ante-version
Normal is 12֯
Describe the acetabulum?
Facing obliquely forward, outward and downward
Covered in Articular cartilage
High Repetitive Loading of the hip____-____x force of BW during movement
High Repetitive Loading of the hip = 4-7x force of BW during movement
How is motion of the patellofemoral joint summarized?
Motion summarized as rolling, sliding, and combination of roll/slide
What is the motion of the patellofemoral joint restricted by?
Restricted by the ACL and PCL
Describe the different loads that the knee can experience based on different positions?
With increased flexion at the knee, >90deg, compression increases because of the changed orientation of the force vectors and increased tension requirement in the quadriceps to maintain body position.
Normal Walking = 1/3rd body weight, compression force
Stair climbing = 3x body weight
Squatting = HIGHLY stressful to knee
Describe the spine?
Mechanically, the annulus fibrosis behaves as a coiled spring, holding the vertebral bodies together.
The nucleus pulposus acts like a ball bearing that the vertebrae roll over during flexion/extension and lateral bending.
During lifting, both compression and anterior shear act on the spine. Tension in the spinal ligaments and muscles contributes to compression.
What are the four ligaments of the glenohumeral joint?
Superior GH Ligament
Middle GH Ligament
Anterior Band of IGHLC (inferior glenohumeral ligament complex)
Posterior band IGHLC (inferior glenohumeral ligament complex)
What does the superior GH ligament do?
Limits Anterior & Inferior translation in arm at 0 deg of ABD
What does the middle GH ligament do?
Limits Anterior translation at arm 45 Deg ABD
What does the anterior band of IGHLC do?
Limits Anterior translation beyond 45 Deg ABD + External Rotation
What does the posterior band of the IGHLC do?
Limits Posterior translation 45 Deg ABD + Internal Rotation
What does the labrum do?
The labrum enhances the depth of the glenoid fossa by 50%.
What is the resting position of the scapula?
Resting position of the scapula
2in from midline btw 2nd -7th ribs
The scapula?
Internal Rotation of ____-____ deg from frontal plane
Anterior Tipping of ____-____ deg from frontal plane
Upward Rotation of ____-____ deg from sagittal plane
Internal Rotation of 30-45 deg from frontal plane
Anterior Tipping of 10-20 deg from frontal plane
Upward Rotation of 10-20 deg from sagittal plane
The scapula never moves in isolation becase it connects the the ____ and ____ joints?
The scapula never moves in isolation becase it connects the the AC and SC joints
When arm abducts the scapula undergoes ____ rotation, ____ rotation, and ____ tipping?
When arm abducts the scapula undergoes upward rotation, external rotation, and posterior tipping
How many degrees of rotation available are available in the scapula due to clavicular elevation and posterior rotation?
60°
What two functions do muscles do that attach to the scapula?
Muscles attaching to the scapula have 2 functions:
-Stabilize the scapula when shoulder is loaded
-Move and position scapula for shoulder movement
What three mechanisms stabilize the glenohumeral joint?
Passive tension (in the rotator interval capsule)
Air tight capsule (producing negative intraarticular pressure)
Glenoid inclination – (slight upward tilt of glenoid fossa.)
-Either anatomically or bc of upward rotation of scapula
Most of the time, Force of contraction by the ____ causes humerus and humeral head translation to be superior?
Most of the time, Force of contraction by the Deltoid causes humerus and humeral head translation to be superior
Becuase the deltoid produces a ____ force instead of a ____ force, the deltoid is ____ to independently abduct the arm and another ____ set of forces is needed to work with the deltoid?
Becuase the deltoid produces a shear force instead of a compressive force, the deltoid is unable to independently abduct the arm and another synergistic set of forces is needed to work with the deltoid
What is the role of the biceps brachii in glenohumeral stabilization?
The long head of the biceps may produce its effect by tightening the relatively loose superior labrum and transmitting increased tension to the superior and middle GH ligaments.
The Biceps muscle is capable of contributing to the force of flexion and can, if the humerus is laterally rotated, contribute to the force of abduction and anterior stabilization.
Without ____ sliding of the articular surface of the humeral head, the humeral head will roll up the glenoid fossa and ____ upon the ____ ____. (Subacromial bursa, Rotator cuff tendons and Long Head of biceps tendon). Slight ____ ____ of the center of the humeral head can still occur during humeral abduction despite inferior sliding of the head’s articular surface (1-2mm)
Without downward sliding of the articular surface of the humeral head, the humeral head will roll up the glenoid fossa and impinge upon the coracoacromial arch. (Subacromial bursa, Rotator cuff tendons and Long Head of biceps tendon). Slight superior translation of the center of the humeral head can still occur during humeral abduction despite inferior sliding of the head’s articular surface (1-2mm)
Which three muscles of the rotator cuff have a similar line of pull?
Infraspinatus, teres minor and subscapularis muscles individually or together have a similar line of pull
How does the rotator cuff work?
Infraspinatus, teres minor and subscapularis muscles individually or together have a similar line of pull
These muscles function gradually increasing from 0-115º of elevation after which 115-180 it drops.
Initial range of elevation, these muscles work to pull the humeral head down and during middle range, these muscles act to externally rotate for clearing greater tubercle under coracoacromial arch
Subscapularis helps as internal rotator when arm is at side and during initial range.
More Abd decreases internal rotation capacity and then it acts with other Rotator cuff muscles to promote compression.
The Rotatory component (Fy) compresses as well as rotates and the translator component (Fx) helps offset the superior translator pull of the deltoid
The Supraspinatus has a ____ directed translator component (fx) and a rotatory component (Fy) that is more ____ than that of the other rotator cuff muscles and can ____ ____the humerus?
The Supraspinatus has a superiorly directed translator component (fx) and a rotatory component (Fy) that is more compressive than that of the other rotator cuff muscles and can independently abduct the humerus.
When is the supraspinatus activated?
Supraspinatus activity starts when the passive tension in rotator internal capsule is insufficient as in a loaded arm
First 15º. Then joins with deltoid
What are the four properties of muscle?
Extensibility – Capacity to Stretch or ↑ in length
Elasticity – ability to return to normal shape following a stretch
Irritability – Can respond to stimulus
-Intrinsically through Action potentials and Electrochemical responses
-Extrinsically through an external stimuli
Ability to develop tension – the contractile component of muscle which is unique to itself
Expanding upon Elasticity produces what 2 major components of elastic muscle behavior?
Parallel Elastic Component (PEC)
-When muscle is stretched passively the muscle membranes supply resistance
Series Elastic Component (SEC)
-Housed in the tendon, operating like a spring that stores elastic energy when tensed muscle is stretched.
Both prallel elastic component and seris elastic component are named because of ____________________?
PEC runs ____ to contractile components but works only passively?
SEC runs ____ with the contractile component of muscle tissue?
Both behaviors are named because of their anatomical position and response during movement.
PEC runs parallel to contractile components but works only passively
SEC runs in series with the contractile component of muscle tissue
What it a muscle cell?
Muscle fiber
Muscle fibers bundled together become a ____ which bundled again becomes a ____ ____?
Muscle fibers bundled together become a Fascicle which bundled again becomes a muscle belly.
What is a motor unit?
Motor Unit – The single motor neuron and all the fibers innervated by it
A Motor Neuron subdivides its axon for individual fiber supply through a motor end plate
Only 1 motor end plate per muscle fiber.
Large muscles have a large number of ____ ____ ____ small muscles only require a small ____ ____?
Large muscles have a large number of motor unit response small muscles only require a small fiber response
Fast Twitch vs Slow Twitch
FT fibers work in ____ the time of ST fibers.
FT are ____ in diameter
FT are more____ than ____ ST fibers
FT _____ faster than ST
Fast Twitch vs Slow Twitch
FT fibers work in 1/7th the time of ST fibers.
FT are larger in diameter
FT are more white than red ST fibers
FT fatigues faster than ST
What are the two general types of muscle fiber arrangements?
Parallel – runs with the longitudinal axis
-Fibers shorten with contraction
-Take body segments through greater ROM than pennate muscles
Pennate – fibers are angled and rotate when contracted
-Angle of pentation that is greater than 60deg decreases the force transfer by more than ½ of the force actually produced
-Contain more fibers per unit of muscle volume
Generate more force than parallel muscles of same size
What is the advantage of parallel fibers?
Parallel – runs with the longitudinal axis
-Fibers shorten with contraction
-Take body segments through greater ROM than pennate muscles
What is the advantage of pennate fiber arrangement?
Pennate – fibers are angled and rotate when contracted
-Angle of pentation that is greater than 60deg decreases the force transfer by more than ½ of the force actually produced
-Contain more fibers per unit of muscle volume
-Generate more force than parallel muscles of same size
What is the formua for finding the force of a pennate fiber arrangement?
F(total)= F(fibers) x cos (angle)
An Active Muscle does 1 thing ……. ____ ____?
An Active Muscle does 1 thing ……. Develop Tension
What is an agonist?
Agonist – Mover
Contraction
What is an antagonist?
Antagonist – Opposer
Eccentric tension
“Brakes” action
What are stabilizers?
Stabilizers – muscles stabilize a part of the body against a specific force
What are neutralizers?
Neutralizers – prevent unwanted accessory actions
(Pronator teres neutralizes supination during elbow flexion)
What order does muscle fiber recruitment occur in?
Muscle fiber recruitment starts with the Nervous system
Slow twitch fibers always recruited 1st
Lower threshold and easy to recruit
Increased demand for force, speed, or duration → trigger increases in muscle fiber recruitment.
Slow → Fast a → Fast b
What are the three different types of contractions?
Change in muscle length as a result of muscular tension and the response of torque at the joint.
Concentric, Torque> resistive joint torque
Isometric , Torque = 0
Eccentric, Torque < tension in muscle with
developed tension
“Putting on the brakes”
Floppy Arms and legs without Eccentric tensions
What is a twtich?
Twitch like fibers produce tension quickly from a single stimulus
Quick rise and fall of tension
Repeated stimulus creates additional rises in tension over time which is known as a ____?
Repeated stimulus creates additional rises in tension over time which is known as a summation
____ occurs when the muscle is producing a sustained max tension from the repeated stimulus?
Tetanus occurs when the muscle is producing a sustained max tension from the repeated stimulus
What is the length-tension relationsihip?
The relationship between length before stimulation and subsequent tetanic tension development
Each muscle has an optimal length for developing tension
Optimal length correlates with max overlap of thick and thin filaments
Max isometric tension is dependent on muscle length
Total tension = ____ ____ (muscle fibers) + ____ ____ (tendons and muscle membranes)
Total tension = Active Tension (muscle fibers) + Passive tension (tendons and muscle membranes)
Parallel fibers = max tension just over ____ ____?
Parallel fibers = max tension just over resting length
Pennate fibers = max tension at ____-____% resting length?
Pennate fibers = max tension at 120-130% resting length
Describe the force velocity relationship?
Defined as: the greater the load against which a muscle must contract, the lower the velocity of that contraction
As the velocity of concentric action increases, force produced during the action decreases
Max force is determined by velocity of shortening(concentric) or lengthening (Eccentric)
At zero velocity (static action), myosin cross bridges can easily attach to the actin sites because they have no time constraints.
Therefore, we have maximal crossbridge interaction and maximal force output.
The stronger the muscle the greater the magnitude of its isometric max on the force velocity curve.
As velocity of contraction increases, the thin filament moves past the thick filament at a faster rate.
Not enough time for long cross bridge connections. Force Diminished bc of attach and detach rate.
Describe the power comprimise in muscle contraction?
Power = Force * Velocity
Muscle Power = Muscle force * velocity muscle shortening
Max power happens at 30% max velocity and 30% max concentric force
Lift at 1/3rd of 1rep max
Peak power values at 200-300deg/sec
Strong doesn’t always mean powerful
Explosive movements are based on the ability to generate power
Fast twitch fibers are a huge asset for Muscle power.
Describe the stretch shortening cycle?
Stretch-Shortening cycle : Phenomenon of enhanced force by generating Eccentric action immediately prior to concentric action
-Muscle can perform significantly more work when stretched prior to shortening
-Eccentric immediately followed by concentric contraction, NO PAUSE
-Greater work results with low metabolic costs.
-Often involving the stretch reflex to enhance force development
SSC is the basis for plyometric training
What is the extra work in the stretch shortening cycle attributed to?
Stored elastic energy (tendon, crossbridge, and titin)
Eccentric phase elicits a stretch reflex.
Eccentric phase pre-loads the muscle, so the concentric phase begins at a higher force (length/tension, slow-twitch).
Two joint muscles (rectus femoris, gastrocnemius) transfer energy and allow the muscle to work at a lower velocity and a higher force.
How do we know what is happening in a muscle?
Galvani discovered that:
Muscle responds when electrically stimulated
Muscle produces a detectable current when developing tension.
Electromyography studies neuromuscular function
Helpful in studying, assessing, and treating muscle injuries and recruitment abnormalities
