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adaptations to resistance training

Introductory Terminology. Disinhibition: reducing the inhibition of muscle action by reflex protective mechanisms.Size Principle: motor neurons with low threshold, slow twitch velocity, and small diameter are recruited first, with progressively larger and higher threshold neuron recruitment as more force is required.Synchronization: simultaneously recruiting motor units..

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adaptations to resistance training

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    1. Adaptations to Resistance Training Exercise Physiology

    3. Effects of Neuromuscular Training

    4. Effects onNeuromuscular Systems Neural Control Biochemical Muscle Cells Capillary Supply Muscle Enlargement Fiber Hypertrophy versus Fiber Hyperplasia Muscle Atrophy Fiber Type Alteration

    5. Neural Control Nervous system elicits greater muscular force by: Innervating more motor units Increasing rate of firing motor units Resistance training enables voluntary recruitment of highest threshold neurons so can maximally activate muscle. Resistance training activate motor units in coordinated fashion for more efficient recruitment pattern. Improved synchronization of motor units.

    6. Neural Control Possible increased neural activation of the muscle by activating higher threshold fast motor units first and inhibit slow motor units to enhance the rate of force development. Neural reflex facilitation and disinhibition or reduced autogenic inhibition of motor neurons (inhibit GTOs). Reduced inhibition by antagonist.

    7. Neural Adaptations Submaximal tasks require involvement of less muscle mass. Hypertrophic responses in neuromuscular junction in both high- and low-intensity groups: Increased end plate perimeter length & area Enhanced dispersion of Ach receptors

    8. Neural Control Initial increase in expression of strength due to improved neural control of muscle contraction.

    9. Neural Drive Electromyographic studies indicate lower level in EMG activity to muscular force ratio. Muscle produced more force with lower amount of EMG activity. More force with less neural drive. The increase in maximal neural drive to muscle increases maximal strength.

    10. Biochemical Changes Equivocal increases in concentration of muscle creatine, phosphocreatine, ATP, and glycogen. Enzyme activity of ATP-PC (creatine phospho-kinase, myokinase) increased with isokinetic training. Little or no change in activity of ATP-PC enzymes with resistance training. Increase or no change in glycolytic enzyme activities by resistance training. Small but significant increases in aerobic enzyme activities in high volume-short rest.

    11. Muscle Cells Myoglobin content in muscles following strength training may decrease. Mitochondrial density has been shown to decrease with resistance training because of dilution effects of muscle fiber hypertrophy.

    12. Capillary Supply Increase number of capillaries in a muscle helps support metabolism and contributes to total muscle size. Improved capillarization has been observed with resistance training by body builders but decreased in power and weight lifters. Increase of capillaries linked to intensity and volume of resistance training. Time course of changes in capillary density slow (more than 12 weeks).

    13. Muscle Enlargement Resistance training adaptation is enlargement of muscles. Enlargement of muscles thought to be due primarily to muscle fiber hypertrophy. Transient hypertrophy: tissue edema Chronic hypertrophy: structural changes

    14. Muscle Hypertrophy Muscle enlargement is generally paralleled by increased muscle strength. Increased muscle strength is NOT always paralleled by gains in muscle size. Increase in cross-sectional fiber area of both ST and FT muscle fibers. FT fiber area appears to increase to greater extent than ST fiber area.

    15. Fiber HypertrophyversusFiber Hyperplasia Increased size of individual fibers due to: more myofibrils more actin & myosin more sarcoplasm more connective tissue surrounding fiber Increased number of individual fibers muscle fibers split longitudinally observed in cats with intense training cross-sectional studies in humans

    16. Fiber Type Alteration Neither speed (anaerobic) nor endurance (aerobic) training could alter basic fiber type in early studies Only motor neuron cross innervation could alter fiber types Specific training improves specific metabolic capacities

    17. Muscle Atrophy Immobility causes decrease in muscle size Atrophy primarily affects ST muscle fiber types

    18. Connective Tissue and Bone Supporting ligaments, tendons and fascia strengthen as muscle strength increases. Connective tissue proliferates around individual muscle fibers, this thickens and strengthens muscle’s connective tissue harness. Bone mineral content increases more slowly, over 6- to 12-month period.

    19. Effect on Cardiovascular System

    20. Heart Rate Short-term resistive training studies show no change or small insignificant changes of about 5 to 12% in resting Heart Rate. Changes attributed to decreased sympathetic and increased parasympathetic drive to heart.

    21. Blood Pressure Training effects of regular resistive training on resting blood pressure are inconsistent. Some short-term studies have shown increases in SBP as a result of high-intensity training. Most studies of resistive training show either no difference or slight decreases in systolic or diastolic blood pressures.

    22. Resting Cardiovascular Adaptations

    23. Acute Cardiovascular Responses

    24. Cardiac Morphology

    25. Cardiac Morphology Left ventricular concentric hypertrophy resulting from resistive training can be accompanied by strengthened myocardium and increased stroke volume at rest and during exercise. Stroke volume is not significantly increased when it is related to body surface area or lean body mass.

    26. Serum Lipids The effect of resistance training on the lipid profile are inconsistent. Short-term training studies are also inconclusive. Both positive effects and no effect have been shown in serum lipids as a result of resistive training. Volume of training appears to be a primary factor affecting serum lipids.

    27. Body Composition Adaptations For the most part, Small decreases in body fat Minimal increases in total body mass Minimal increases in FFM, about 0.3 kg/weekly

    28. Muscular Soreness Acute muscular soreness occurs during and immediately following the exercise period. Muscular contraction causes ischemia. Because of ischemia, metabolic waste products accumulate and stimulate pain. Delayed muscular soreness occurs 24 to 48 hours after exercise session has stopped. Torn tissue theory. Spasm theory. Connective tissue theory. Appears consistent with research.

    29. Muscular Soreness

    30. Muscle Soreness Excessive mechanical forces cause minute tears in muscle connective tissue with release of creatine kinase, myoglobin and troponin 1. Tissue injury initiates inflammatory reaction in damaged muscle. Elements of inflammatory process include increased blood flow and tissue permeability.

    31. Muscle Soreness Physiological purpose of inflammatory process is to rid cells of damaged tissue & prepare the tissue for repair. Edema and chemical substances (PGE2) stimulate muscle afferents & increase sensitivity of pain receptors. Inflammatory reaction causes secondary chemical reaction through formation of oxygen radicals, proteases, phospholipids and nitric oxide. This is initiated early in the injury process, but full manifestation is 1-3 days after beginning DOMS.

    32. Muscle Soreness Inflammation is followed by healing phase and formation of protective proteins. There are increases in growth factors, collagen, and fibronectin fragments, enzyme inhibitors, oxygen scavengers, and remodeling collagenase. This process heals the tissue and makes muscle resistant to further incidence of DOMS from subsequent exercise sessions.

    33. Muscle Soreness Treatment Theoretical basis for most DOMS treatments has been to target inflammatory response. For every study demonstrating effectiveness of NSAIDs, another reports little or no effectiveness. Massage & cryotherapy (targeting blood flow) have proven largely ineffective. Currently, no strong evidence to support other therapies such as homeopathy, warm-up, stretching, TENS, ultrasound, nutritional supplements, or acupuncture. Sayers, S.P. 2007. GSSISayers, S.P. 2007. GSSI

    34. Muscle Soreness Treatment Simple truth may be once muscle damage initiated, little can be done to halt the damage process & soreness. Solution: prevent occurrence through gradual adaptation to exercise. Pre-conditioning of muscle: chronic yoga Gradual habituation to eccentric contractions.

    35. Illustration References McArdle, William D., Frank I. Katch, and Victor L. Katch. 2006. Essentials of Exercise Physiology, 3rd ed. Image Collection. Lippincott Williams & Wilkins. Plowman, Sharon A. and Denise L. Smith. 1998. Digital Image Archive for Exercise Physiology. Allyn & Bacon.

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