KIN365 Neuromuscular Aspects of Muscle Tissue
KIN365 Neuromuscular Aspects of Muscle Tissue KIN 365
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This 6 page Class Notes was uploaded by Jess Snider on Tuesday February 16, 2016. The Class Notes belongs to KIN 365 at University of Alabama - Tuscaloosa taught by Colleen Geary in Spring2015. Since its upload, it has received 43 views.
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Date Created: 02/16/16
Neuromuscular Aspects of Muscle Tissue Skeletal muscle tissue has four main neuromuscular properties related to its ability to produce force & movement about joints Contractibility Extensibility Contractibility Neuromuscular Aspects of Muscle Tissue: Irritability/Excitability Irritability/excitability The sensitivity or responsiveness of a muscle to a stimulus-either chemical, electrical, or mechanical I.e. muscles are considered irritable because can receive & respond to a signal Without irritability. Excitability, muscles wouldn’t fire=no movement Review Signal sent is specifically called an action potential Action potentials are sent, by way of the spinal cord, through the somatic nervous system (which is part of the peripheral nervous system) which is responsible for the delivery of efferent or motor nervous impulses to outlying regions of the body(arms, legs, fingers, toes, etc.) This function allows for ALL OTHER neuromuscular functions of muscle including contractibility, extensibility and elasticity Neuromuscular Aspects of Muscle Tissue: Contractility Contractility The ability of muscle to change shape, contract (become shorter & thicker), and develop tension or internal force against resistance, if & only if, appropriate stimulus (action potential) is provided I.e. muscles can develop tension Ex: some people can lift enormous amounts of weight This property is unique to skeletal muscles I.e. other body tissues do NOT have this property Allows for muscle contractions, tension development, power production which lead to strength & endurance Neuromuscular Aspects of Muscle Tissue: Extensibility Extensibility Ability of a muscle to be passively stretched & extended beyond its normal resting length I.e. can stretch a muscle & all that runs through it Ex: triceps brachii stretched beyond its normal resting length when elbow flexors contract to achieve full elbow flexion Allows for contractibility & flexibility Neuromuscular Aspects of Muscle Tissue: Elasticity Elasticity Ability of a muscle to return to its original or normal resting length following a stretch Given the chance, once stretched, a muscle will spring back into original position Ex: bubble gum vs. rubber band Both elastic A rubber band will spring back more towards original shape than bubble gum because much more elasticity Muscle is more like rubber band than bubble gum Allows for flexibility Neuromuscular Aspects of Muscle Tissue With these properties, skeletal muscle can exhibit: Flexibility Strength Endurance Power Neuromuscular Aspects of Muscle Tissue: Flexibility Flexibility Muscle can stretch through a small or large range of motion Dependent on the joint I.e. just because flexible @ hip does not mean flexible @ hamstring Neuromuscular Aspects of Muscle Tissue: Strength Strength The component of muscle force that produces torque at the joint Measured as a function of the collective force-generating capability of a given functional muscle group I.e. maximal force can produce at one period of time with one muscle or muscle group Measured with 1 rep max= 1 repetition at maximal weight Factors that affect strength(4): Training state of muscle With both concentric & eccentric strength training, gains in strength over approximately first 12 weeks appears to be related to neuromuscular adaptation, and not increase in cross-sectional area Neuromuscular adaptation: the improved innervation of the trained muscle; includes: Increased neural firing rates Increased excitability Increased levels of motor output from the CNS (more action potentials sent through efferent pathways) Muscle cross-sectional area Relates to tension-generating capabilities of muscle Occurs beyond first 12 weeks of strength training Force arm Distance between muscle attachment to bone & joint center Angle of muscle attachment to bone Remember, maximum when the muscle is oriented at 90 degree angle to the bone with a change in the angle of the orientation in either direction progressively diminishing the amount of force produced Neuromuscular Aspects of Muscle Tissue: Endurance Endurance The ability of the muscle to exert tension over time The longer the tension is exerted, the greater the endurance I.e. repeated submaximal force development Measured over time or by the number of reps can do at certain submaximal amount of force Important note about training for endurance: Endurance training does NOT increase muscle fiber diameter, as training for strength does May be why this is the preferred method of training for females, as they don’t want to “bulk-up” Uses slow twitch muscle fibers( don’t fatigue quickly) Neuromuscular Aspects of Muscle Tissue: Power Power Factors that affected power: Muscular strength (force production at muscle) Movement speed (velocity) Important for anaerobic activities that require explosive movements, such as Olympic weight lifting, throwing, jumping, sprinting Therefore, FT muscle fibers are an asset for individuals training for power(FGF to be exact) The rate at which work is performed The product of muscular FORCE & the VELOCITY of muscle shortening The rate of force or torque production @ joint Muscle power Work Force∗Displacement Power= Time = Time =work or force* velocity =work * velocity Can also describe power as how long it takes to develop force I.e. if develop a great deal of force in a short amount of time =large amount of power Muscle Power: force production per unit time How quickly can you generate a lot of force Two important factors: Force of contraction Velocity of movement (time) Power= force* velocity (P=f*v) With relation to concentric contraction: Force=small Velocity= fast (takes a little time, time= small) Power= force *velocity =small*small LITTLE POWER …faster concentration contractions produce less force than any type of slow contractions Force=large Velocity =slow (takes a lot of time, time=large) Power=force*velocity =large*large =A WHOLE LOT OF POWER …slower concentration contractions with a larger resistance produce greater force than any fast concentric contractions and slow concentric contractions with less resistance Neuromuscular Aspects of Muscle Tissue: Power Final Statement Question: How do we generate maximum or peak power? Peak power occurs @: Intermediate level of velocity Beyond 30% of maximal velocity, power production decrease & Intermediate level of muscle shortening & tension generation If not stretched beyond 70-80% of resting length, ability to develop contractile tension & exert force is essentially reduced to zero If stretched beyond 120-130% of resting length, significant decrease in the amount of tension a muscle can develop & amount of force a muscle can exert Neuromuscular Aspects of Muscle Tissue: Injuries When training for flexibility, strength, endurance, & power, skeletal muscle can exhibit: Fatigue Strains Contusions Cramps DOMS Compartment Syndrome Neuromuscular Aspects of Muscle Tissue: Fatigue Fatigue An exercise-induced reduction in the maximal force capacity over time of muscle The opposite of endurance The ore rapidly a muscle fatigues, the less endurance it has Fatigue may occur in: The muscle fiber The motor unit itself (inhibiting ability to generate an action potential=no muscle twitch or contraction) Variety of factors affect rate of fatigue of muscle Type & intensity of exercise Specific muscle groups involved in exercise Physical environment in which the activity occurs Muscle fiber type & pattern of unit activation Cause of Fatigue: Inconclusive, but postulations include: Reduction in rate of intracellular calcium release & uptake by sarcoplasmic reticulum This is a major theory thoughts to be best explanation Increases in muscle acidity & intracellular potassium levels Decreases in muscle energy supplies & intracellular oxygen Characteristics of fatigue: Reduction of muscle force production capabilities Reduction of shortening velocity Prolonged relaxation of motor units between recruitment Prolonged twitch duration Prolonged sarcolemma action potential of reduced amplitude Neuromuscular Aspects of Muscle Tissue: Strains Strains Overstretching of a muscle tissue Magnitude of injury related to size of overload & rate of overloading Severity & symptoms of strain can be: Mild Minimal structural damage Feelings of tightness or tension in muscle Moderate Partial tear in muscle tissue Symptoms include pain, weakness, loss of function Severe Severe tearing of muscle Functional loss, accompanying hemorrhage, & swelling Most frequently strained muscle in human body: Hamstrings (lack of flexibility; 2 joint muscle-suffer passive insufficiency) Neuromuscular Aspects of Muscle Tissue: Contusions Contusions Muscle bruises Caused by: compression forces sustained during impacts Symptoms: hematomas within muscle tissue Can lead to development of much more serious condition called myositis ossificans, or calcification within the muscle : Cramps Cramps Include moderate to severe muscle spasms with proportional levels of accompanying pain Causes: Etiology is not well understood Possible factors include: Electrolyte imbalances Deficiencies in calcium & magnesium Dehydration Neuromuscular Aspects of Muscle Tissue: DOMS Delayed Onset Muscle Soreness(DOMS) Occurs after some period of time following unaccustomed exercise Arises 24-72 hours after participating in long or strenuous bout of exercise (hints name DELAYED, as it is not immediate) Caused by : Micro tearing of muscle tissue Symptoms include: Same kind of histological change that accompany acute inflammation Pain Swelling Reduced range of motion Neuromuscular Aspects of Muscle Tissue: Compartment Syndrome Compartment Syndrome Hemorrhage or edema within a muscle compartment Caused by: injury or excessive muscular exertion Pressures increase within the compartment causing severe damage to neural & vascular structures within compartments following the absence of pressure release Characterized by progressive: Swelling Discoloration Diminished distal pulse Loss of sensation Loss of motor function
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