KIN 365 Chp. 3 Notes
KIN 365 Chp. 3 Notes KIN 365
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This 7 page Class Notes was uploaded by Taylor Fendley on Tuesday February 9, 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 44 views. For similar materials see Applied Biomechanics in Kinesiology at University of Alabama - Tuscaloosa.
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Date Created: 02/09/16
Chapter Three Neuromuscular Aspects of Muscle Tissue (chp. 2 in Manual) 1. Skeletal muscle tissue has four main neuromuscular properties related to its ability to produce force and movement about joints a. Irritability/Excitability i. The sensitivity or responsiveness of a muscle to a stimulus—either chemical, electrical, or mechanical ii. Muscles are considered irritable because they can receive and respond to a signal iii. Without irritability/excitability, muscles wouldn’t fire, resulting in no movement iv. This function allows for ALL OTHER neuromuscular functions of muscle—including contractility, extensibility, and elasticity 1. There would be no movement at the joints b. Contractility i. The ability of the muscle to change shape, contract (become shorter and thicker), and develop tension or internal force against resistance, if and only if the appropriate stimulus (action potential) is provided ii. This property is unique to skeletal muscles iii. Allows for muscle contraction, tension development, and power production which leads to strength, power and endurance c. Extensibility i. The ability of a muscle to be passively stretched and extended beyond its normal resting length ii. Ex. Triceps brachii stretched beyond its normal resting length when elbow flexors contract to achieve full elbow flexion iii. Allows for contractility and flexibility d. Elasticity i. The ability of a muscle to return to its original or normal resting length following a stretch ii. Given the chance, once stretched, a muscle will spring back into original position 1. Ex. Bubble gum vs. rubber band 2. Both are elastic, but a rubber band will spring back more toward its original shape more than bubble gum due to higher elasticity iii. Allows for flexibility 2. With these four properties, skeletal muscles can exhibit flexibility, strength, endurance, and power a. Flexibility i. Muscles can stretch through a small or large range of motion ii. Dependent on the joint 1. Just because you’re flexible at the hip doesn’t mean you’re flexible at the hamstring b. Strength i. The component of muscle force that produces torque at the joint ii. Measured as a function of the collective force-generating capability of a given functional muscle group iii. The maximal force can produced at one period of time with one muscle or muscle group iv. Measured with 1 rep max 1. One repetition at maximal weight v. Important to measure in order to work out at a certain percentage of your overall strength vi. Factors that affect strength 1. Training state of the muscle a. With both concentric and eccentric strength training, gains in strength over approximately the first 12 weeks appears to be related to neuromuscular adaptation, and not increase in cross-sectional area b. Neuromuscular adaptation: the improved innervation of the trained muscle, includes: i. Increased neuronal firing rates ii. Increased excitability 1. More muscle fibers responding to increased action potentials 2. Motor unit recruitment iii. Increased levels of motor output from the CNS 1. More action potentials sent through efferent pathways 2. Muscle cross-sectional area a. Relates to tension-generating capabilities of muscle b. Occurs beyond the first 12 weeks of training c. Grows your muscle fibers—hypertrophy i. The size, not the number d. More actin and myosin are able to form cross-bridges when this area is increased e. The training state of the muscle and the muscle cross- sectional area are the two factors affecting strength that we DO have control over 3. Force arm a. Distance between muscle attachment to bone and joint center b. Depends on the length of our bones c. Changes up until our bones stop growing i. 17-18 for females ii. 21-22 for males d. Not something we have control over 4. Angle of muscle attachment to bone a. Remember, the maximum strength is reached when the muscle is oriented at 90 degrees to the bone, with a change in angle of the orientation in either direction progressively diminishing the amount of force produced b. Not something we have control over c. Endurance i. The ability of the muscle to exert tension over time 1. The longer the tension is exerted, the greater the endurance ii. Endurance training requires submaximal force development 1. Measured over time, or by the number of reps you can do at a certain submaximal amount of force iii. Endurance training does NOT increase muscle fiber diameter like strength training does 1. This is why it’s the preferred method of training for females, because it doesn’t “bulk you up” d. Power i. The rate at which work is performed ii. The product of muscular force and the velocity of muscle shortening iii. The rate of force or torque production in iv. Factors that affect power 1. Muscular strength (force production at muscle) 2. Movement speed (velocity) v. Important for anaerobic activities that require explosive movements, such as Olympic weight lifting, throwing, jumping, sprinting 1. Therefore, FT muscle fibers are an asset for individuals training for power vi. Muscle power 1. Work or force x velocity a. Work x velocity 2. Can also describe power by how long it takes to develop force 3. If a great deal of force is developed in a short amount of time, it generates a large amount of power vii. Force production per unit time 1. How quickly can you generate a lot of force 2. Two important factors a. Force of contraction b. Velocity of movement (time) 3. Power = force x velocity a. P = f x v 3. With Relation to Concentric Contraction a. Force = small b. Velocity = fast i. Takes a little time, time = small c. Power = force x velocity i. Small x small ii. Little power d. Faster concentration contractions produce less force than any type of slow contractions i. Force= small ii. Velocity= large 1. Takes a lot of time, time = large iii. Power = force x velocity 1. Small x large 2. Intermediate power e. Slower concentration contractions produce less force than any type of slow contractions i. Force= large ii. Velocity= slow 1. Takes a lot of time, time= large iii. Power= force x velocity 1. Large x large 2. A whole lot of power f. Slower concentration contractions with a larger resistance produce greater force than any fast concentric contractions and slow concentric contractions with less resistance 4. Power: Final Statement a. How do we generate maximum or peak power? b. Peak power occurs at: i. Intermediate level of velocity ii. Beyond 30% of maximal velocity 1. Power production decreases iii. Intermediate level of muscle shortening and tension generation iv. If not stretched 70-80% of resting length, ability to develop contractile tension and exert force is essentially reduced to zero v. If stretched beyond 120-130% of resting length, significant decrease in the amount of tension a muscle can develop and amount of force can exert 5. Injuries a. When training for flexibility, strength, endurance, and power, skeletal muscles can exhibit: i. Fatigue 1. Exercise-induced reduction in the maximal force capacity over time of muscle 2. The opposite of endurance a. The more rapidly a muscle fatigues, the less endurance it has 3. Fatigue may occur in: a. The muscle fiber or in the motor unit itself (inhibiting ability to generate an action potential = muscle twitch or contraction 4. Variety of factors affect rate of fatigue: a. Type and intensity of exercise b. Specific muscle groups involved in exercise c. Physical environment in which the activity occurs d. Muscle fiber type and pattern of motor unit activation 5. Causes of fatigue: a. Inconclusive but postulations include: b. Reproduction in rate of intracellular calcium release and uptake by sarcoplasmic reticulum i. Major theory, thought to be best explanation c. Increase in muscle acidity and intracellular oxygen 6. Characteristics of fatigue: a. Reduction of muscle force production capabilities b. Reduction of shortening velocity c. Prolonged relaxation of motor units between recruitment d. Prolonged twitch duration e. Prolonged sarcolemma action potential of reduced amplitude ii. Strains 1. Overstretching of a muscle fiber 2. Magnitude of injury related to: a. Size of overload b. Rate of overloading 3. Severity and symptoms of strains can be: a. Mild i. Minimal structural damage ii. Feelings of tightness or tension in muscle b. Moderate i. Partial tear in muscle tissue ii. Symptoms include 1. Pain 2. Weakness 3. Loss of function c. Severe i. Severe tearing of muscle ii. Functional loss, accompanying hemorrhage and swelling 4. Most frequently strained muscle in the body is the hamstrings iii. Contusions 1. Muscle bruises 2. Caused by: a. Compression forces sustained during impacts 3. Symptoms: a. Hematomas within muscle tissue 4. Can lead to development of much more serious condition called myositis ossificans, of calcification within the muscle iv. Cramps 1. Include moderate to severe muscle spasms with proportional levels of accompanying pain 2. Etiology is not well understood a. Cause is unknown 3. Possible factors include: a. Electrolyte imbalances b. Deficiencies in calcium and magnesium c. Dehydration v. DOMS 1. Delayed Onset Muscle Soreness 2. Occurs after some period of time following unaccustomed exercise a. Arises 24-72 hours after participating in long or strenuous bout of exercise b. Hints name delayed, as it is not immediate 3. Caused by microtearing of muscle tissue 4. Symptoms: a. Same kind of histological change that accompany acute inflammation i. Pain—relatively mild to severe ii. Swelling b. Reduced range of motion c. Symptoms alleviated with rest vi. Compartment Syndrome 1. Hemorrhage or edema within a muscle compartment a. Exceptionally painful, but more rare than other injuries 2. Caused by: a. Injury or excessive muscular exertion b. Pressures increase within the compartment causing severe damage to neural and vascular structures within compartments following the absence of pressure release i. The only way to reduce the pressure is to cut the muscle open and release the buildup 3. Characterized by progressive: a. Swelling b. Discoloration c. Diminished distal pulse d. Loss of sensation e. Loss of motor function
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