Biomechanics of skeletal muscle

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muscle cramps (what are they caused by, how can we prevent them)

-Electrolyte imbalances, deficiencies in calcium and magnesium and dehydration -Stretch -More Sodium -Ease into a Workout Program

FT fibers- what type of muscle contraction, and what type of activities?

-fast powerful muscular contraction -good for sprinting, and jumping

what is a motor unit?

-single motor neuron and all fibers it innervates -considered the functional unit of the neuromuscular system -100 - 2000 fibers

type 1 slow twitch fibers (oxidative) (contraction speed, fatigue rate, diameter)

-slow -slow -small diameter

what is muscular endurance?

-the ability of muscle to exert tension over a period of time -the opposite of muscle fatigability

what is muscular power? (2 equations and 1 def)

-the product of muscular force and the velocity of muscle shortening (F×V) -the rate of torque production at a joint -the product of net torque and angular velocity at a joint (M×ω)

why are series and parallel elastic components named as they are?

-they are named this because the membranes and tendons are either parallel, or in series (in line) with the muscle fibers, which provides the contractile component

how can the elastic components exert significant influences on the production of muscle force, power, and work?

. During quick, rapid movements, they can increase muscle power by storing the work of muscle contraction and releasing it rapidly. Alternatively, the elastic components can release energy more slowly to stretch the muscle contractile component during an activity such as landing from a jump, dissipating energy, and serving to protect the muscle from damage

4 properties of musculotendinous unit?

1-extensibility 2-elasticity 3-irritability 4-ability to develop tension

common muscle injuries (5)

1-strains 2-contusions 3-cramps 4-delayed onset muscle soreness 5-compartment syndrome

The length of electromechanical delay (EMD) is?

20-100ms between stimulation and initiation of tension The length of EMD varies considerably among human muscles, with values of 20-100 msecreported (21). Researchers have found shorter EMDs produced by muscles with high percentages of FT fibers as compared to muscles with high percentages of ST fibers

Delayed-Onset Muscle Soreness

24-72 hrs after exercise micro-tearing of the muscle tissues

A muscle directly involved in causing a segment to move is called what? A.agonist B.antagonist C.neutralizer D.stabilizer

A

A single muscle cell is called what? A.fiber B.neuron C.unit D.none of the above

A

During the first 12 weeks of resistance training, strength gains are due primarily to what? A.improved innervation of the muscle B.increase in cross-sectional area C.both A and B D.none of the above

A

During the kicking and follow-through phases of a punt, the quads are experiencing what type of contraction? A.concentric B.eccentric C.isometric D.isokinetic

A

In which of the following activities do the biceps brachii function as antagonists? A.straightening the elbow during a push-up B.straightening the elbow during a pull-up C.curling a barbell from the floor to waist height D.both A and B

A

When the wrist is flexed, the finger flexors cannot produce as tight a fist as when the wrist is in a neutral position. This is an example of what? A.active insufficiency B.passive insufficiency C.both A and B D.none of the above

A

Where is the series elastic component (SEC) of a muscle found? A.tendons B.ligaments C.muscle membrane D.all of the above

A

Which of the following is a unique behavioral property of muscle tissue? A.ability to develop tension B.extensibility C.irritability D.all of the above

A

Which of the following statements is true? A.When movement is slow, slow twitch fibers are recruited first. B.When movement is fast, fast twitch fibers are recruited first. C.Both A and B are true. D.None of the above are true.

A

Which of the following types of muscle tension is commonly used as a braking mechanism to slow limb movement? A.eccentric B.isotonic C.concentric D.isometric

A

bi-articular muscle

A muscle that crosses two joints

A contraction in which there is not a change in length is called what? A.dynamic B.isometric C.concentric D.isokinetic

B

During the down phase of a knee extension exercise, what role does the hamstring group play? A.agonist B.antagonist C.stabilizer D.neutralizer

B

Muscle hypertrophy in humans is primarily due to what? A.increase in number of muscle fibers B.increase in size of muscle fibers C.both A and B D.none of the above

B

The component force which is parallel to the moving bone and acts to pull the bones together at the joint is called what? A.curvilinear force B.stabilizing force C.rotary force D.dislocating force

B

The elasticity of human skeletal muscle tissue is believed to be due primarily to which of the following? A.the parallel elastic component B.the series elastic component C.the continuous elastic component D.the active elastic component

B

The opposite of muscular endurance is what? A.muscular strength B.muscular fatiguability C.muscular power D.muscular flexibility

B

What type of muscle contraction is employed by the elbow flexors when slowly lowering your backpack to your desk? A.concentric B.eccentric C.isometric D.isokinetic

B

Which behavioral property of muscle tissue is defined as "the ability to respond to a stimulus"? A.elasticity B.irritability C.extensibility D.contractility

B

Which of the following does not characterize a pennate muscle? A.relatively strong B.fibers parallel to long axis of muscle C.relatively low range of motion D.all of the above are true

B

Which of the following is/are characteristic of fast-twitch oxidative glycolytic fibers? A.Contraction speed is intermediate (faster than type I but slower than type IIB). B.Fatigue rate is intermediate (faster than type I but slower than type IIB). C.both A and B D.none of the above

B

Which of the following most accurately describes a motor unit? A.a single muscle fiber and a single motor neuron B.a single motor neuron and all muscle fibers it innervates C.a single muscle fiber and several motor neurons D.none of the above

B

Which of the following statements represents the force-velocity relationship for muscle tissue? A.contraction is faster when the load is heavier B.contraction is slower when the load is heavier C.contraction is slower when the load is lighter D.the speed of contraction is not affected by the nature of the load

B

Which of the following terms best describes the rate of torque production at a joint? A.mechanical work B.muscular power C.muscular energy output D.muscular strength

B

Which of the following types of strength training is particularly associated with subsequent muscular soreness? A.concentric B.eccentric C.isometric D.all of the above

B

During the execution of a pull-up when the chin is over the bar, which force exerted by the biceps brachii is greatest at the elbow? A.the rotary force B.the stabilizing force C.the dislocating force D.the "pinching" force

C

In human skeletal muscle, force generation capability is highest in which of the following conditions? A.muscle is at resting length B.muscle is slightly shortened C.muscle is slightly lengthened D.muscle length is irrelevant to force production

C

The amount of torque a muscle group can generate at a joint is used to measure what? A.muscular power B.muscular endurance C.muscular strength D.muscular flexibility

C

The torque of a muscle (rotary component) is greatest in what position? A.when the moment arm is longest B.when the muscle insertion is 90° to the bone C.both A and B D.position does not effect torque

C

Which of the following is a potential disadvantage of multijoint muscles? A.active insufficiency B.passive insufficiency C.both A and B D.none of the above

C

Which of the following likely contributes to the stretch-shortening cycle? A.the series elastic component B.muscle spindle activity C.both A and B D.none of the above

C

Which of the following statements is/are true? A.Pennate muscles are capable of producing more tension per unit of cross-sectional area than parallel muscles. B.Parallel muscles are capable of producing more range of motion than pennate muscles. C.Both A and B are true. D.Neither A nor B is true.

C

Which of the following time periods is termed electromechanical delay? A.the time required for conduction of the nerve impulse to the neuromuscular junction B.the time required for the nerve impulse to cross the neuromuscular junction C.the time required for the muscle to initiate the development of tension after receipt of the nerve impulse D.the time required for a muscle to reach peak tension after the development of tension is initiated

C

Which type of muscle could serve as an antagonist of a flexor? A.abductor B.adductor C.extensor D.rotator

C

compartment syndrome

Compartment syndrome is a painful condition that occurs when pressure within the muscles builds to dangerous levels. This pressure can decrease blood flow, which prevents nourishment and oxygen from reaching nerve and muscle cells. Compartment syndrome can be either acute or chronic. can cause hemorrhage or edema

The force-velocity relationship implies which of the following? A.It is impossible to move a heavy resistance at a fast speed. B.It is impossible to move a light load at a slow speed. C.both A and B D.none of the above

D

When an opposing torque at a joint is greater than the torque created by a muscle, what type of contraction occurs in that muscle? A.isometric B.isotonic C.concentric D.eccentric

D

When flexing the elbow, the biceps brachii, brachioradialis, and brachialis are the three major agonists recruited to perform this movement because all cause flexion at the elbow. However, the biceps also cause supination, an undesired movement. Therefore another muscle acting as a , causing must be recruited to prevent the undesired motion. A.stabilizer, extension B.neutralizer, extension C.stabilizer, pronation D.neutralizer, pronation

D

Which of the following is a behavioral property of muscle tissue? A.ability to develop tension B.extensibility C.irritability D.all of the above

D

Which of the following is true regarding the parallel elastic component (PEC) of muscular elasticity? A.This component is provided by the muscle membranes. B.This component provides resistance when a muscle is passively stretched. C.This is the component primarily responsible for the elasticity of muscle. D.both A and B E.all of the above

D

Which of the following is true regarding the stretch-shortening cycle? A.When a muscle is stretched just prior to contraction, the resulting contraction is more forceful. B.An eccentric contraction is followed by a concentric contraction. C.The SSC promotes storage of elastic energy. D.both A and B E.all of the above

E

Which of the following is/are characteristic of muscle fatigue? A.reduction in muscle force B.reduction in shortening velocity C.prolonged relaxation of motor units between recruitment D.both A and B E.all of the above

E

eccentric strength training

Eccentric strength training involves the use of resistances that are greater than the athlete's maximum isometric force generation capability. As soon as the load is assumed, the muscle begins to *lengthen*

A high percentage of FT fibers is advantageous for generating ____ movements, and a high percentage of ST fibers is beneficial for activities requiring ___.

FT-better for fast movements ST-better for activities involving endurance

what is passive insufficiency?

It occurs when a muscle cannot elongated any farther without damage to its fibers (this is done passively). restriction of joint range of motion when muscles are fully stretched (decreased ROM for wrist extension with the fingers extended inability of a two-joint muscle to stretch enough to allow full range of motion at both joints at the same time

increasing speed, force, or duration of movement involves progressive recruitment of

MUs with higher and higher activation thresholds -smaller then larger (size principle)

what is a myofibril?

Many of these units make up a single muscle fiber. -myofibrils hold actin and myosin and made of many sarcomeres

isometric contraction

Muscle contracts but there is no movement, muscle stays the same length (pushing into a wall, not moving)

high-frequency stimulation (tetanus)

Produces stronger twitches than low-frequency stimulation

what is elasticity due to primarily? sec or pec

SEC-series elastic component

ST fibers-what type of activity?

ST fibers-great for endurance distance running, cycling, swimming

what does the sarcoplasm contain?

Sarcoplasm of each fiber contains mitochondria, nuclei, and thread like myofibrils that are aligned parallel to one another. The myofibrils contain two types of protein filaments whose arrangement produces the striated pattern after which skeletal, or striated muscle is named

what is active insufficiency?

The point at which a muscle cannot shorten any farther due to contracting. Two-joint muscles can fail to produce force when slack (active insufficiency) Active- condition occurring when a two-joint muscle cannot shorten enough to cause full range of motion at both joints it crosses at the same time Muscles are too relaxed and unable to form a fist

what is eccentric training more beneficial for compared to concentric?

This type of training has been found to be more effective than concentric training in increasing muscle size and strength. As compared with concentric and isometric training, however, eccentric training is also associated with delayed onset muscle soreness

force velocity relationship

When the force is neglible, muscle contracts with maximum velocity. (more force, less velocity. Less force, more velocity)

can exercise change muscle fibers?

Yes, exercise training over time can result in changes in fiber types within an individual.

from a mechanical perspective, the musculotendinius unit behaves as _______ with ______ in parallel with _______ (muscle membranes) and in series with another elastic component (___)

a contractile component muscle fibers elastic component tendons

what does a muscle's viscoelastic property enable the muscle to do? what does viscoelastic mean?

a muscle's viscoelastic property enables it to progressively lengthen over time when stretched Viscoelastic=having the ability to stretch or shorten over time -when you stretch your muscle, it doesn't just recoil super quickly. it takes time, which is called viscoelastic

what is muscle irritability

ability to respond to a stimulus

what is elasticity?

ability to return to normal resting length following a stretch

purpose of series elastic component

acts as a spring to store elastic energy when a tensed muscle is stretched

agonist

acts to cause a movement

neutralizer

acts to eliminate an unwanted action produced by an agonist

antagonist

acts to slow or stop a movement

stabilizer

acts to stabilize a body part against some other force

two factors known to affect muscle fiber types

age and obesity -regular high intensity exercise can reduce the loss of motor units associated with aging

4 roles of a muscle

agonist, antagonist, stabilizier, and neutralizer

what is the ability to develop tension

also known as contraction -the contractile component of muscle function

the same number of fibers present at birth is apparently maintained through life, except for the occasional loss from injury. the increase in muscle size after resistance training thus is generally believed to represent _____

an increase in fiber diameters rather than the number of fibers themselves

more stretch, more

available force for the muscle

three types of muscle contractions

concentric, eccentric, isometric

sarcomere (when is it large vs small)

contractile unit of a muscle fiber -develops depending on the amount of overlap between the actin and myosin -if overlap is large, length of sarcomere is decreased

sarcomere

contractile unit of a muscle fiber. composed of alternating dark and light bands that give muscle its striated appearence

mono-articular muscle

crosses only one joint

physiological cross sectional area

cut the muscle perpendicular to the muscle fibers . pennant or parallel

anatomical cross sectional area

cut the muscle perpendicular to the muscle line or body. along the tendon line (B)

isometric muscle contraction

develops tension without changing length

what is the stretch shortening cycle?

eccentric contraction followed immediately by concentric contraction When an actively tensed muscle is stretched just prior to contraction, the resulting contraction is MORE FORCEFUL than in the ABSENCE of the prestretch

both the SEC and PEC have a viscous property which allows what?

enables a muscle to stretch and recoil in a time dependent fashion

FT fibers can be converted to ST fibers with what type of training? FT IIb can be converted to IIa with _______?

endurance training (FT-->ST) heavy resistance training

type IIB fast twitch-glycolytic (contraction speed, fatigue rate, diameter)

fast fast large

type IIA fast twitch-oxidative glycolytic (contraction speed, fatigue rate, diameter)

fast intermediate intermediate

types of fibers

fast twitch and slow twitch

fast twitch (FT) fibers vs slow twitch fibers

fast-reach peak tension and relax more quickly. slow-takes a lot longer to reach peak tension and takes longer to relax

parallel fiber arrangement

fibers are roughly parallel to the longitudinal axis of the muscle sartorius, biceps brachii

the stronger a muscle, the _____ the magnitude of its isometric maximum on the force-velocity curve

greater

Individuals genetically endowed with a high percentage of FT fibers may gravitate to sports requiring ____, and those with a high percentage of ST fibers may choose _______ sports. However, the fiber type distributions of both elite strength-trained and elite endurance-trained athletes fall within the range of fiber type compositions found in untrained individuals.

high FT fibers-strength high ST-endurance

summation

increased force of contraction by a skeletal muscle fiber when a twitch occurs before the previous twitch relaxes building in an additive fashion. multiple signals and summation can occur and tension is progressively elevated until a maximum value for that fiber is reached

eccentric ____muscle size and strength by _______ the muscle

increases, by lengthening

muscle gets longer, force _______ muscle gets shorter, force _____

increases, decreases

-although all fibers in a motor unit are the same type, most skeletal muscles contain both fast twitch and slow twitch fibers, with the relative amounts varying from muscle to muscle

k

what does a longer PCSA mean?

larger force capability

PCSA are _____ than ACSA in pennant muscle fibers

longer

When an actively tensed muscle is stretched just prior to contraction, the resulting contraction is _____ FORCEFUL than in the ABSENCE of the ______

more forceful prestretch without stretch first, muscle cannot produce as much force

a muscle can perform substantially _____ work when it is actively ______ prior to shortening than when it simply contracts

more, stretched

most large muscles have a _____ type of fiber (fast vs slow twitch)

most large muscles are mixed fiber types

contusions

muscle bruises caused by compressive forces sustained during impacts myositis ossificans

what is tension capability of the muscle tissue affected by? (3)

muscle cross sectional area (anatomical cross sectional area ACSA and physiological crosss sectional area PCSA) training state of muscle and moment arms

eccentric contraction

muscle lengthens as it maintains tension

contractile component

muscle property enabling tension development by stimulated muscle fibers

muscle tension development capability is less following _______

muscle shortening

multi-articular muscle

muscle that crosses three or more joints

amount of maximum isometric tension a muscle is capable of producing is partly dependent on the _______

muscles length

is muscle fiber composition different across genders?

no. it is the same

are all muscle fibers the same length>

no. some fibers run the entire length of a muscle; others are shorter

is it impossible to move a heavy object at a fast speed?

not impossible to move a heavy resistance at a fast speed though. The stronger the muscle is, the greater the magnitude of maximum isometric tension (maximum amount of force that a muscle can generate before actually lengthening as the resistance is increased)

muscle strains

overstretching of muscle tissue hamstrings are the most frequently strained

types of fiber arrangement

parallel and pennate

what are the two major components of elastic behavior of a muscle?

parallel elastic component (PEC) and series elastic component (SEC)

where is the parallel elastic component derived from?

passive elasticity derived from *muscle membranes*

where is the series elastic component derived from?

passive elasticity derived from *tendons* when a tensed muscle is stretched

which type of fiber has higher peak tension?

peak tension is typically greater for fast twitch fibers than slow twitch

two types of muscle architecture

pennant (like a feather) or parallel

what does a longer PCSA mean for the pennant fibers?

pennant fibers are better for force production capacity

examples of stretch-shortening cycle

plyometrics, baseball pitching

movements that are precisely controlled, such as those of the eyes or fingers, are produced by motor units with ____ numbers of fibers. -gross, forceful movements, such as those produced by the gastrocnemius, are usually the result of the activity of ____ motor units

precise movements-small number of fibers gross movements-large motor units, many fibers

single stimulus

present one at a time in random order and the person's reaction to each is recorded

Repetitive stimulation of muscle fibers

produces contractions of longer duration and greater tension than a single twitch

relaxed vs contracted sarcomere

relaxed-large sarcomere contracted-small sarcomere

with warm up, there is a shift to the ______ in the force-velocity curve, with _______ maximum isometric tension and _______ maximum velocity of shortening possible at a given load

right higher higher

what is the membrane surrounding the muscle fiber?

sarcolemma

what is the specialized cytoplasm in the sarcolemma called?

sarcoplasm

pennate fiber arrangement

short fibers attach to one or more tendons within the muscle. like a feather and can be quantified

concentric contraction

shortening of muscle

tension doesn't necessarily mean the muscle is ______

shortening. tension could be stretching the muscle as well

what is a muscle fiber?

single muscle cell

how can muscle fibers grow?

skeletal muscle fibers grow in both length and diameter from birth through adulthood

in single muscle fibers, force generation is at its peak when the muscle is _______

slightly stretched

which type of fibers are always recruited first

slow twitch fibers

which fibers are easier to activate?

slow twitch fibers are easier to activate than fast twitch fibers

what is eccentric training associated with

soreness and structural damage later on

tetanus

state of muscle producing sustained maximal tension resulting from repetitive stimulation

stimuli affecting muscles are either ____ or _____

stimuli affecting muscles are either electrochemical, (action potential from an attached nerve), or mechanical (external blow to a portion of a muscle)

within human body, muscles at rest are under passive tension due to their elastic properties, but tension capabilities increased when muscle is slightly _____

stretched

the myofibril has a ____ appearence

striated/striped gives skeletal muscle its appearence

total tension

sum of the active tension provided by muscle fibers and passive tension provided by the tendons and muscle membranes

purpose of parallel elastic component

supplies resistance when a muscle is passively stretched

when activated by a stimulus, a muscle responds by developing

tension

what factors impact muscular strength?

tension generating capability of the muscle tissue

what is extensibility?

the ability to be stretched or to increase in length

contractility-

the ability to shorten its length

how do we measure muscular strength?

the amount of torque a muscle group can generate at a joint

ACSA and PCSA are the ______ cut for parallel muscle fibers

the same

where does the force length curve come from

the sarcomere

what is the effect of muscle temperature (warm up)?

the speeds of nerve and muscle functions increase

thin filament vs thick filament

thin=actin thick=myosin actin binds to myosin during sliding filament theory

how can muscle fiber diameter be increased?

through resistance training

electromechanical delay

time between the arrival of neural stimulus and tension development by the muscle

what covers myosin binding sites on actin?

tropomyosin calcium reaches the tropomyosin and it is removed to expose the actin binding sites on the myosin head

what factor affects muscular force generation?

velocity

what are moment arms of the muscles crossing the joint affected by? (2)

•distance between muscle attachment to bone and joint center •angle of the muscle's attachment to bone


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