Exam 2 Kinesiology

Types of contractions

-Concentric: Muscle shortens while producing tension -Isometric: Muscle length does not change while producing tension -Eccentric: Muscle lengthens while producing tension

What is the advantage of the stretch shortening cycle?

-Utilizes elastic response and muscle spindles to increase force output -Beyond increased force output, there is also an improvement in muscular efficiency

Besides pennation angle, MU recruitment, and fiber type, there are several other factors that influence force generation:

-Velocity of muscle contraction -Length of the muscle -Length of time since stimulus

the number of muscle fibers in a human body

-genetically determined -what is present at birth is maintained throughout life -muscle strengthening is a result in an increase in fiber diameter and not number of fibers

A volleyball player complains of decreased spiking performance and anterior shoulder pain. After evaluation, you determine that her pain is mainly notable when her arm is raised in the ranges of approximately 60 to 120 degrees of abduction, but no real pain is noticed below or above these ranges. Based on this information the most likely injury she is experiencing is subacromial impingement , and the most likely cause of this injury is tight or overactive internal rotator muscles . A possible solution to this problem is to strengthen the external rotator muscles .

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Active insufficiency is the inability of a multi-joint muscle to produce sufficient force at one joint when the muscle is slack at another joint.

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In carpal tunnel syndrome, the wrist/hand flexor tendons pass through a tunnel created by the carpal bones on the dorsal side, and the flexor retinaculum on the ventral side. If/when the tendons become inflamed due to over-activity, the tendons swell and put pressure on the median nerve which also passes through this tunnel. The pressure placed on this structure is what causes the pain and numbness the person experiences.

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The scapulohumeral rhythm describes how the shoulder joint is able to accomplish such large ranges of motion . In approximately the first 30 degrees of humeral elevation, the scapula is responsible for about 20% of the movement by way of upward rotation . Beyond 30 degrees of humeral elevation, this bone increases it's contribution to about 33% . Additionally, the clavicle is important in this movement since it also elevates approximately 35 to 45 degrees at the sternoclavicular joint.

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The type of impingement syndrome called internal impingement is experienced when the supraspinatus is pinched between the greater tubercle of the humerus and the posterior-superior rim of the labrum. This is likely experienced when a person places their shoulder in abduction and external rotation .

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434 muscles in body

40-45% total body weight 150 muscles responsible for movements and posture

What is the difference between a shoulder separation and a shoulder dislocation?

A shoulder separation is a detachment of the clavicle from the acromion, while a dislocation occurs at the glenohumeral joint

Describe the active tension curve of the length-tension relationship graph and why it is a parabola shape. (Hint: think about what is going on at the level of the sarcomere.)

Active tension is produced when the muscle is stimulated to contract.The level of attachment of the myosin heads of the sarcomere is represented in the curve. At around 50% length of the sarcomere, there is a decrease in force because some of the myosin heads are blocked from binding to actin. Why? At 100% lengthening of the sarcomere, all the myosin heads are attached to actin, and Titin is still coiled but not overstretched. This is the point of the most force in muscle. After 100%, the curve goes downwards creating the parabola shape. This is because as the muscle lengthens, less myosin heads are interacting with the actin, which produces less force. Why? The sarcomere is being stretched so the myosin heads are being pulled away from the actin

•The central nervous system (CNS) has an amazing amount of control on our movements (smooth, precise, and delicate movements can be produced effortlessly) •There is a systematic recruitment by MUs when performing any movement 1.Slow twitch (Type 1): low threshold and easy to activate

As the force speed or duration of the activity requires other motor units are recruited Type 2a and 2b have higher thresholds and are harder to activate during low intensity exercise, the CNS may recruit type 1 fibers exclusively, as fatigue sets in, type 2 units are recruited

What is the name of the muscle located in the forearm that is responsible for elbow flexion?

Brachioradialis

Describe carpel tunnel syndrome and explain why it causes pain and/or numbness in the wrist and hand.

Carpal tunnel syndrome occurs when there is excessive wrist activity-mostly related to flexion. The flexor tendons and median nerve are surrounded by walls created by the carpal bones and the flexor retinaculum. The excessive wrist activity causes the flexor tendons to swell and increase pressure inside the walls of the flexor retinaculum which can ultimately pinch the median nerve. When the nerve is pinched it causes pain, numbness, and lack of use of the fingers.

Titin

Coiled at rest and unravels when stretched

Is it easier or harder to do bicep curls with a pronated grip or a supinated grip? Why?

Easier with a supinated grip because the biceps are not in active insufficiency

•When a muscle is stimulated, there is a lag time between the onset of stimulation and onset of force production (20-100 ms) •This is the time required for the contractile component (muscle) to stretch the SEC (tendon) before tension begins to develop •Muscles with higher percentage of FT fibers have a shorter EMD •Training can decrease the EMD (resulting in faster reaction time) •EMD is longer: -Immediately following passive stretching (a possible reason stretching inhibits explosive movements) -Several days after eccentric exercise -After a period of endurance training -In children compared to adults

Electromechanical delay

What is the primary action(s) of the latissimus dorsi? Select all that apply. Extend the shoulder Abduct the shoulder Flex the shoulder Adduct the shoulder Elevate the scapula Upward rotate the scapula Externally rotate the shoulder Horizontally adduct the shoulder

Extend the Shoulder Adduct the Shoulder

What is the difference between intrinsic and extrinsic muscles of the hand?

Extrinsic muscles originate outside of the hand, while intrinsic muscles originate inside the hand

What two muscles in the forearm are primarily responsible for wrist flexion? (Select only two) Palmaris Longus Flexor Digitorum Superficialis Flexor Carpi Radialis Flexor Digitorum Profundus Flexor Carpi Ulnaris Extensor Carpi Ulnaris Extensor Carpi Radialis Longus and Brevis

Flexor Carpi Radialis Flexor Carpi Ulnaris

Which muscles are responsible for radial deviation? (select all that apply) Flexor carpi radialis Flexor carpi ulnaris Extensor carpi radialis longus Extensor carpi radialis brevis Extensor carpi ulnaris Palmaris longus Extensor pollicis longus

Flexor carpi radialis extensor carpi radialis longus extensor carpi radialis brevis

Dislocations

GH joint most commonly dislocated in the body (Anterior, posterior, inferior (less common) directions superior not common. 90% dislocations occur anteriorly: when humerus is abducted, extended and externally rotated most other dislocations are posterior: opposite are positions than anterior: flexed, adducted, and internally rotated

What is the purpose of the labrum?

Improve the fit and stability of the glenohumeral joint

Which of the following neurological changes occur during the first few weeks of weight training? Select all that apply. Increased motor neuron excitability Increased inhibitory neural pathways Increased number of motor units recruited by the central nervous system Increased rate of neural stimulation Increased pre-synaptic inhibition Increased rate of potassium uptake

Increased motor neuron excitability Increased number of motor units recruited by the central nervous system increased rate of neural stimulation

SC Joint

Modified ball and socket proximal end of clavicle articulates with the sternum (clavicular notch of manubrium) and cartilage of the first rib

motor unit

Motor Units: Single motor neuron and all the muscle fibers it innervates -Axon of motor neuron subdivides many times so each fiber is supplied with an endplate -Usually only 1 endplate per fiber -typically confined to a single muscle -A single motor unit may innervate as many as 2000 muscle fibers (large gross movements) and as few as 5 (fine movements)

Type I SLAP Tear

No labral detachments, but some labral fraying

Describe the passive tension curve of the length-tension relationship graph. Why does it start at 100% of resting length and not before?

Once the percentage is past 100%, Titin begins to have passive tension. Passive tension occurs as a recoil tension. Titin is a naturally coiled protein, so as it is stretched, tension increases (similar to a rubber band). The reason why this does not happen before 100%, is because before then titin was not yet stretched to the point where it could produce a recoil tension.

1. Describe shoulder impingement syndrome. Discuss practical ways to rehab from this injury. (Which specific muscles should you target?)

Shoulder impingement syndrome is the most common shoulder injury, and results in loss of function and disability (p. 186). It occurs when there is an increased pressure within a confined anatomical space and damages the enclosed tissues. There are two types which are internal and subacromial impingement. Often, lesions of the tendons are also occurring along with impingement. When someone has subacromial impingement, you can tell because only some degrees of motion are painful (for example between 60-120 degrees). This type of impingement occurs when the shoulder is forcibly abducted and the supraspinatus tendon, subacromial bursae, and the proximal tendon of the long head of the biceps brachii are pushed against the anterior surface of the acromion and coracoacromial ligament. This condition can also be worsened by different anatomical variations between people. Acromioplasty is a treatment option, which involves a surgical procedure that removes a piece of the bone that is in contact with the tissues being pinched. Other than that, I would think that resting the supraspinatus, and long head of the biceps brachii would be good. Resting those muscles would mean less external rotation and shoulder elevation. The other type of impingement is internal. This occurs when the movement of shoulder abduction with external rotation traps the supraspinatus tendon (and sometimes infraspinatus) between the greater tubercle of the humerus and the posterior-superior rim of the glenoid. This injury usually occurs with rotator cuff damage and is common in athletes like baseball pitchers. The supraspinatus is the most common muscle injured. Besides surgery, resting the supraspinatus could help (which includes minimal movements that involve external rotation and abduction).

During the downward phase of a push up, list what movements are occurring, the planes the movements are occurring in, and the primary mover responsible for the movement at the shoulder, elbow, and wrist. For this question, assume the push up is performed with the elbows in contact with the torso. Fill out the table below for your answer. Shoulder Elbow Wrist

Shoulder- extension, sagittal, latissimus dorsi, pectoralis major, teres major Elbow- flexion/pronation, sagittal/transverse, brachialis, brachioradialus, prontator quadratus Wrist- hyper-extension, sagittal, extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris

How does the stretch-shortening cycling increase force production? (include both elastic force production and muscle spindle reflex in your answer)

Stretching an actively tensed muscle before a contraction allows the muscle to create more force than not stretching it. The full mechanism behind the stretch-shortening cycle is not fully understood yet, but they believe that the elastic component of muscles is involved. The recoil force of muscle (due to its elasticity) and the reflex of muscle spindles likely enhances the force production. There are three phases involved. The 1st phase is the eccentric phase; this is where the muscle spindle is stimulated and the SEC/PEC store elastic energy. The second is a short phase called the amortization phase. This is when there is a transition between eccentric loading and concentric propulsion, and more energy is stored. The last phase is the concentric phase. This phase is characterized by the quick release of the stored energy and the reflex of the muscle spindle. The summation of the steps causes an increase in the force production.

Type II SLAP Tear

Superior part of the labrum detaches from the rim of the glenoid but the biceps tendon remains intact

Type IV SLAP tear

Superior part of the labrum tears with a bucket-handle pattern and a part of the biceps tendon detaches

Type III SLAP tear

Superior part of the labrum tears with a bucket-handle pattern but the biceps tendon remains intact

If you have inflammation, pain, and swelling on the lateral side of your elbow, what possible injury might exist?

Tennis elbow - because this occurs when the wrist extensors are overactive

Explain how the use of a pronated grip as compared to a supinated grip affects the performance of a bicep curl.

The biggest reason is that one grip causes the bicep to be in active insufficiency while the other grip does not. Active insufficiency involves a multi-joint muscle not shortening enough to produce full force across all joints (p. 150). During pronation of the hand, the radius crosses over the ulna and the main muscles being used for this motion are the pronator quadratus (primary) and the pronator teres (assist). The biceps are in active insufficiency during a protonated grip because their insertion point (the radial tuberosity) is brought closer to the origin of the muscle, slackening the muscle. During supination, the main muscles being affected are the biceps brachii and the supinator. For a more effective bicep curl (if the person performing the bicep curl wants to mainly work the biceps), the arm should be supinated so that the biceps are not in active insufficiency and can be used to perform both supination and flexion effectively.

Identify the common name for lateral epicondylitis and explain how it occurs.

The common name for lateral epicondylitis is "tennis elbow." This injury includes inflammation or microdamage to tissues on the lateral side of the distal humerus. The damage also affects the tendinous attachment of the extensor carpi radialis brevis and sometimes the extensor digitorum. Having previous conditions such as De Quervain's disease, carpal tunnel, oral corticosteroid therapy, and smoking history make a person more susceptible to a lateral epicondylitis injury. When playing tennis, a person exerts a lot of force on the elbow, especially when playing with poor form. The racket is often held away from the body which increases torque. Several muscles originate on the lateral epicondyle of the elbow, which are referred to as the extensors. When the extensors are used excessively, the lateral epicondyle becomes strained due to the extensor muscles pulling on it and it causes the lateral epicondyle to have pain, inflammation, and swelling.

Identify the common name for medial epicondylitis and explain how it occurs.

The common name for medial epicondylitis is "Little Leaguer's elbow" or "golfer's elbow." This injury affects the tissues on the medial aspect of the distal humerus. It can be derived from medial epicondylar apophysitis, medial epicondyle avulsion, or an ulnar collateral ligament tear from excessive tensile forces. The medial epicondyle is the origin of the wrist flexors. Excessive action of wrist flexors pulls on medial epicondyle and causes pain, inflammation, and swelling in the medial epicondyle. Wrist flexion during a pitch, causes excessive pulling from the strain of the flexors, and it can result in medial epicondylitis. During a pitch, (1) at the beginning of the pitch there is a valgus strain on the medial aspect of the elbow then (2) the rest of the body is brought forward before the forearm and hand which results in (3) injury to the medial aspect of the distal humerus due to the valgus strain.

the directional arrangement of muscle fibers are important for how the muscle functions

The directional arrangement of the muscle fibers are important for how the muscle functions •Two main types of fiber arrangements -Parallel: Fibers are approximately parallel to the longitudinal axis of the muscle •Examples: sartorius, rectus abdominis, biceps brachii favor greater length changes (larger ROM) also called longitudinal -Pennate: Fibers lie at an angle to the longitudinal axis of the muscle •Examples: tibialis posterior, gastrocnemius, rectus femoris, deltoid favor greater force production and faster contraction velocity increased number of fibers per cross sectional are The angle of pennation increases as tension progressively increases in the muscle fibers

Describe in detail the glenoid labrum. What is this structure made of, and how does it add stability to the joint?

The glenoid labrum is a rim of soft tissue on periphery of the glenoid and is composed of dense collagenous tissue, part of joint capsule, tendon of long head of biceps brachii, and glenohumeral ligament. The glenoid labrum adds stability to the glenohumeral joint. It adds stability by deepening the fossa so that there is more surface area for the humerus to attach to.

Identify the three most common fractures of the hand and wrist and the most common scenario in which they would occur.

The most common fractures of the hand and wrist occur at the distal radius, the scaphoid, and the lunate bones (p. 203). Distal radius fractures occur when a person falls on a hyperextended wrist. A scaphoid fracture commonly occurs when a person falls on an outstretched hand with most of the weight landing directly on the palm. A lunate bone fracture occurs with extreme ulnar deviation and a large force being exerted on the lunate; this could also happen during a fall.

What is nursemaid's dislocation in the elbow?

The radial head is detracted from beneath the annular ligament and typically then moves lateral

Describe the rotator cuff. What is this structure made of, and how does it add stability to the joint?

The rotator cuff is a band of tendons of the subscapularis, supraspinatus, infraspinatus, and teres minor, which attach to the humeral head. These tendons form a collagenous cuff around the glenohumeral joint. The rotator cuff contributes to the rotation of the humerus. The supraspinatus, infraspinatus, and the teres minor help with lateral rotation while the subscapularis helps with medial rotation. The rotator cuff surrounds the shoulder on the anterior, posterior, and superior sides, the tension of which pulls the head of the humerus toward the glenoid fossa, adding stability to the joint. The rotator cuff muscles, and the biceps also work together to provide shoulder stability before the humerus moves.

Explain the scapulohumeral rhythm in detail

The scapulohumeral rhythm is a description of the range of motion that we can get out of the shoulder complex and the degrees of which the joints between the scapula, humerus, and/or clavicle contribute to the movement. There is a consistent pattern to the ratios of movement between the joints, which is why it is referred to as a rhythm. The rhythm facilitates humeral abduction (p. 176). The scapulohumeral rhythm is best understood divided into 3 parts. 1) For the first 30 degrees of humeral elevation, the scapula contribution is about 1/5 of the total movement. The humerus contributes to a total of 80% of this movement while the scapula contributes about 20%. 2) After 30 degrees, the scapula rotates about 1 degree for every 2 degrees of humeral movement. So total movement in this section is 33% from scapula and 66% from humeral movement. 3) During the first 90 degrees of humeral elevation, the clavicle elevates at the sternoclavicular joint approximately 35-45 degrees.

Describe the total tension curve of the length-tension relationship graph.

The total tension portion of the graph shows the summation of both tensions (passive and active) in the muscle. So it shows the active tension provided by muscle fibers and the passive tension provided by tendons and membranes.

Not including nursemaid's dislocation, what is the most common elbow dislocation? Also, what fracture is commonly associated with this injury?

The trochlear notch of the ulna detaches from the trochlea of the humerus and then the ulna and radius move posteriorly. The common fracture is to the radial head.

Identify and explain the two major components of muscle elasticity.

The two major components of muscle elasticity are parallel elastic component (PEC) and series elastic component (SEC). The parallel elastic component provides resistance when the muscle is passively stretched. The PEC comes from the membranes of the muscle and the protein, Titin. The series elastic component is from the tendons and it stores elastic energy during the tensing of a stretched muscle. Together the PEC and SEC are able to provide stretch and recoil to muscles and allow for the muscle's viscoelastic property.

During a muscle contraction, after calcium has bound to troponin, troponin changes shape which causes tropomyosin to move out of the way of the binding site. The myosin head now has a place to bind on actin and can perform it's power stroke. If you are looking at the sarcomere of the muscle through a microscope, what would you expect to see if the muscle is fully contracted?

Through the lens of the microscope one would see a striated pattern, essentially of the various amounts of overlap between actin and myosin. The bookends of each sarcomere are the Z lines. The actin and Myosin are attached here. The space between the actin filaments (central to the sarcomere) is called the H zone. When the muscle is fully contracted, this space will appear narrowed/closed. The space between the myosin filaments of adjacent sarcomeres is called the I band. In a fully contracted muscle, this space will appear narrowed.

Stretch shortening cycle

Utilization of the energy storage capabilities of the elastic components of the muscle-tendon unit and reflex of muscle spindles to increase force production 3 Phases •Eccentric Phase -Preloading agonist muscle group(s) -SEC/PEC stores elastic energy and muscle spindle is stimulated •Amortization Phase -Transition time between eccentric loading and concentric propulsion-Storage of elastic energy -Duration must be short otherwise the elastic energy is lost as heat •Concentric Phase -Body's response to the energy storage and muscle spindle reflex -Stored elastic energy increases force production in agonist -Reflexive response from muscle spindle stimulation of the agonist muscle

•Many muscles in the body cross two or more joints. •Examples: biceps brachii, long head of triceps brachii, hamstrings, rectus femoris, etc. •These muscles affect motion at both (or all) joints simultaneously. •The effectiveness of a multijoint muscles in causing movement at any one given joint depends on: •Location and orientation of the muscles attachment relative to the joint •Tightness or laxity present in the musculotendinous unit •Actions of other muscles crossing those joints

What are disadvantages associated with muscles that cross more than one joint? •Active Insufficiency: Failure of a multi-joint muscle to produce sufficient force when the muscle is slack •Passive Insufficiency: inability of a multi-joint muscle to stretch enough to allow full range of motion at both joints at the same time

Why are loads on the shoulder so large when the glenohumeral joint is in adduction, compared to when the arm is hanging straight down?

When the arm is adducted, the center of mass of the arm is further away from the shoulder joint center which increases the torque at the shoulder joint

In a fully contracted muscle, this can block the binding of myosin heads, resulting in a decreased force output

actin

Interaction of actin any myosin primarily responsible for producing this.

active tension

bankart lesion

british orthopedist Arthur Bankart (1923)

Common causes of SLAP lesion- superior labrum- anterior to posterior

compression (falls), traction (lifting weights), joint dislocation, throwing (overhead sports)

rotator cuff damage

compromised blood flow from impingement pressures and regions of avascularity near the humeral attachment can also be a result of macrotrauma such as fall or contact sports

Bursae are important for (select all that apply): cushioning muscles from bones managing friction lubricating the joint protecting the shoulder from impact

cushioning muscles from bones managing friction

summation

due to repetitive stimulation

most people have balanced muscle fiber types

endurance trained athletes have larger proportion of slow twitch (type 1) fibers while strength have fast twitch (type 2)

Which components are responsible for elastic tension in a muscle?

epimysium, perimysium, endomysium, titin, tendon

Muscle fatigue

exercise induced reduction of maximal force capacity the more rapid a muscle fatigues the less endurance it has The proportion of ST fibers in a muscle is related to the length of time that a level of 50% maximal isometric contraction can be maintained the specific causes of fatigue are not completely understood -reduction in rate of calcium release or in calcium uptake by sarcoplasmic reticulum -increase in muscle acidity -increase in intracellular potassium -decrease in energy supplies -decrease in intracellular oxygen

musculotendinous unit

extensibility and elasticity muscles have the ability to be stretched and return to resting length after stretched

fast twitch type (type 2)

fast contraction speed, quick fatigue type 2a takes on characteristics of type 1 and type 2 type 2b

wrist movements

flexion, extension, hyperextension, radial deviation, ulnar deviation, circumduction

The load our muscles experience influence the speed at which we can contract our muscles

force velocity relationship

muscular strength

influenced by physiological cross sectional area (PCA) of the muscle tension capability of muscle is approximately 90N/cm sq. the greater the PCA the greater the force output

Muscle soreness is experienced as a result of the muscle undergoing:

large amounts of eccentric exercise

The tension a muscle is capable of producing is influenced by the length of the muscle (this does not mean long vs. short muscles)

length tension relationship

Type 1 AC sprain

ligament stretched

tetanus

maximal force production for the muscle fiber due to high frequency stimulation

muscle fibers are a single muscle cell

multinucleated surrounded by sarcolemma made up of myofibrils (actin and myosin which make a distinct pattern)

muscle elasticity is time sensitive: viscoelastic

muscle stretch maintained over time, the muscle will length (Increased ROM). After it has been stretched it does not recoil immediately but does so slowly overtime quick muscle stretch: muscle returns to its original length immediately (elastic response)

irritability and tension development

muscles respond to stimulus (irritable) -electrochemical and mechanical -muscles can shorten in length by contracting (tension development)

Contain power heads responsible for active force production in the muscle

myosin

It is thought that pain experienced during delayed onset muscle soreness (DOMS):

occurs as a result of microscopic lesions at z lines

elasticity components

parallel elastic component (PEC): provides tension when a muscle is passively stretched- Muscle membranes and Titin Series elastic component (SEC): stores elastic energy to act like a spring when a tensed muscle is stretched (Tendons)

Force that occurs only after the sarcomere is stretched, primarily caused by titin and muscle membranes

passive tension

structural organization of skeletal muscle

sarcoplasmic reticulum and t-tubules provide channels for action potential to enter the muscle cell

slow twitch type (type 1)

slow contraction resist fatigue

myofibril sarcomere

tightly packed filament bundles found within skeletal muscle fibers made up of a series of sarcomeres (basic structural unit of muscle fiber) each sarcomere is separated by z lines and bisected by m lines A band: made up of myosin filaments surrounded by 6 actin filaments I band: contains only actin H zone: contains only myosin

muscle is compartmentalized

total muscle surrounded by epimysium fascicles surrounded by perimysium muscle fiber surrounded by endomysium

Summation of two different forces created within the muscle

total tension

muscle temp

when body temp increases, the speeds of nerve and muscle function increases at elevated temps the activation of fewer motor units is required to sustain a given load the metabolic processes supplying oxygen and removing waste products also quicken muscle function is most efficient at 2 to 3 degrees about normal resting body temp

During a muscle contraction

z-line moves toward A-band I-band narrows and H-zone disappears

Bicep Tendonitis

•Biceps is predisposed to injury because of its intimate involvement with the rotator cuff •The complex interaction of instability and impingement in the shoulder make the cause of biceps tendonitis difficult to identify •Other possible injuries include dislocation from the bicipital groove, tendon rupture, or accompanied SLAP lesion

Movements of the Hand

•CM joints: Thumb similar to ball and socket. Others (2-4) somewhat limited •MP joints (2-4): Flexion, extension, abduction, adduction, and circumduction. Thumb (1): flexion/extension •IP: flexion/extension

Twitch type muscles

•Most skeletal muscles are twitch-type cells that respond to a nerve impulse •A single impulse will cause a rise in tension that peaks in less than 100 milliseconds •BUT, motor units are typically activated by a rapid succession of nerve impulses resulting in Summation, and ultimately tetanus

Muscular power

•Muscle Force x Contraction velocity •Max power occurs at approximately 1/3 of our max velocity and at approximately 1/3 of our max concentric force •Ratio for peak power production by Type 2b, Type 2a, and Type 1 fibers is 10:5:1

DOMS- Delayed onset muscle soreness Describe the most commonly accepted theory of why we experience delayed-onset muscle soreness (DOMS)?

•Muscular soreness caused by eccentric contractions •Not completely understood: thought to be a result of muscular microtrauma •Most commonly accepted theory: -A result of ruptures within the muscle -Ruptures are microscopic lesions at the Z-line of the sarcomere as a result of increased tension force and muscle lengthening from eccentric exercise -May cause actin and myosin cross-bridges to separate prior to relaxation -Nociceptors (pain receptors) within the muscle are stimulated •Research has shown that DOMS is not present in concentric only strength programs The most commonly accepted theory is that during eccentric contractions.It is believed that during eccentric contraction the myosin heads prematurely leave the actin causing microtrauma. This action causes the z-lines of the sarcomere to rupture and the pain receptors are stimulated. The reasoning behind why it is a delayed soreness is currently unknown.

Muscular Strength continued

•Strength during the first 4-6 weeks of training is due more to neural changes rather than muscle hypertrophy -Increased neural firing rates -Increased motor neuron excitability -Decreased pre-synaptic inhibition -Less inhibitory neural pathways -Increased levels of motor unit output from the CNS •After the 4-6 week period, hypertrophy becomes more important