Adaptations to Resistance Training. Resistance Training: Introduction Resistance training yields...
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Transcript of Adaptations to Resistance Training. Resistance Training: Introduction Resistance training yields...
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Adaptations to Resistance Training
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Resistance Training: IntroductionResistance Training: Introduction
• Resistance training yields substantial strength gains via neuromuscular changes
• Important for overall fitness and health
• Critical for athletic training programs
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Resistance Training: Resistance Training: Gains in Muscular FitnessGains in Muscular Fitness
• After 3 to 6 months of resistance training – 25 to 100% strength gain– Learn to more effectively produce force– Learn to produce true maximal movement
• Strength gains similar as a percent of initial strength– Young men experience greatest absolute gains
versus young women, older men, children– Due to incredible muscle plasticity
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Mechanisms of Muscle Strength Gain Mechanisms of Muscle Strength Gain
• Hypertrophy versus atrophy – Muscle size muscle strength
– Muscle size muscle strength– But association more complex than that
• Strength gains result from– Muscle size– Altered neural control
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Figure 10.1Figure 10.1aa
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Mechanisms of Muscle Strength Gain:Mechanisms of Muscle Strength Gain:Neural ControlNeural Control
• Strength gain cannot occur without neural adaptations via plasticity– Strength gain can occur without hypertrophy– Property of motor system, not just muscle
• Motor unit recruitment, stimulation frequency, other neural factors essential
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Mechanisms of Muscle Strength Gain:Mechanisms of Muscle Strength Gain:Motor Unit Recruitment Motor Unit Recruitment
• Normally motor units recruited asynchronously
• Synchronous recruitment strength gains– Facilitates contraction– May produce more forceful contraction– Improves rate of force development
– Capability to exert steady forces
• Resistance training synchronous recruitment
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Mechanisms of Muscle Strength Gain:Mechanisms of Muscle Strength Gain:Motor Unit Recruitment Motor Unit Recruitment
• Strength gains may also result from greater motor unit recruitment– Neural drive during maximal contraction
– Frequency of neural discharge (rate coding)
– Inhibitory impulses
• Likely that some combination of improved motor unit synchronization and motor unit recruitment strength gains
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Mechanisms of Muscle Strength Gain:Mechanisms of Muscle Strength Gain:Muscle HypertrophyMuscle Hypertrophy
• Hypertrophy: increase in muscle size
• Transient hypertrophy (after exercise bout)– Due to edema formation from plasma fluid– Disappears within hours
• Chronic hypertrophy (long term)– Reflects actual structural change in muscle– Fiber hypertrophy, fiber hyperplasia, or both
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Mechanisms of Muscle Strength Gain:Mechanisms of Muscle Strength Gain:Fiber HypertrophyFiber Hypertrophy
• More myofibrils
• More actin, myosin filaments
• More sarcoplasm
• More connective tissue
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Mechanisms of Muscle Strength Gain:Mechanisms of Muscle Strength Gain:Fiber HyperplasiaFiber Hyperplasia
• Humans– Most hypertrophy due to fiber hypertrophy– Fiber hyperplasia also contributes – Fiber hypertrophy versus fiber hyperplasia may
depend on resistance training intensity/load– Higher intensity (type II) fiber hypertrophy
• Fiber hyperplasia may only occur in certain individuals under certain conditions
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Mechanisms of Muscle Strength Gain:Mechanisms of Muscle Strength Gain:Neural Activation + HypertrophyNeural Activation + Hypertrophy
• Short-term in muscle strength– Substantial in 1RM– Due to voluntary neural activation– Neural factors critical in first 8 to 10 weeks
• Long-term in muscle strength– Associated with significant fiber hypertrophy– Net protein synthesis takes time to occur– Hypertrophy major factor after first 10 weeks
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MODEL OF NEURAL AND HYPERTROPHIC FACTORS
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Mechanisms of Muscle Strength Gain:Mechanisms of Muscle Strength Gain:Atrophy and InactivityAtrophy and Inactivity
• Reduction or cessation of activity major change in muscle structure and function
• Limb immobilization studies
• Detraining studies
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Mechanisms of Muscle Strength Gain:Mechanisms of Muscle Strength Gain:Fiber Type AlterationsFiber Type Alterations
• Training regimen may not outright change fiber type, but– Type II fibers become more oxidative with aerobic
training– Type I fibers become more anaerobic with
anaerobic training
• Fiber type conversion possible under certain conditions– Cross-innervation– Chronic low-frequency stimulation– High-intensity treadmill or resistance training
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Muscle SorenessMuscle Soreness
• From exhaustive or high-intensity exercise, especially the first time performing a new exercise
• Can be felt anytime– Acute soreness during, immediately after exercise– Delayed-onset soreness one to two days later
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Muscle Soreness:Muscle Soreness:Acute Muscle SorenessAcute Muscle Soreness
• During, immediately after exercise bout– Accumulation of metabolic by-products (H+)– Tissue edema (plasma fluid into interstitial space)– Edema acute muscle swelling
• Disappears within minutes to hours
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Muscle Soreness:Muscle Soreness:DOMSDOMS
• DOMS: delayed-onset muscle soreness– 1 to 2 days after exercise bout– Type 1 muscle strain– Ranges from stiffness to severe, restrictive pain
• Major cause: eccentric contractions– Example: Level run pain < downhill run pain– Not caused by blood lactate concentrations
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Muscle Soreness:Muscle Soreness:DOMS Structural DamageDOMS Structural Damage
• Indicated by muscle enzymes in blood– Suggests structural damage to muscle membrane– Concentrations 2 to 10 times after heavy training– Index of degree of muscle breakdown
• Onset of muscle soreness parallels onset of muscle enzymes in blood
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Muscle Soreness:Muscle Soreness:DOMS and PerformanceDOMS and Performance
• DOMS muscle force generation
• Loss of strength from three factors– Physical disruption of muscle (see figures 10.8,
10.9)– Failure in excitation-contraction coupling (appears to
be most important)– Loss of contractile protein
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Muscle Soreness:Muscle Soreness:DOMS and PerformanceDOMS and Performance
• Muscle damage glycogen resynthesis
• Slows/stops as muscle repairs itself
• Limits fuel-storage capacity of muscle
• Other long-term effects of DOMS: weakness, ultrastructural damage, 3-ME excretion
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Muscle Soreness:Muscle Soreness:Reducing DOMSReducing DOMS
• Must reduce DOMS for effective training
• Three strategies to reduce DOMS– Minimize eccentric work early in training– Start with low intensity and gradually increase– Or start with high-intensity, exhaustive training
(soreness bad at first, much less later on)
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Muscle Soreness:Muscle Soreness:Exercise-Induced Muscle CrampsExercise-Induced Muscle Cramps
• Frustrating to athletes– Occur even in highly fit athletes– Occur during competition, after, or at rest
• Frustrating to researchers– Multiple unknown causes– Little information on treatment and prevention
• EAMCs versus nocturnal cramps
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Muscle Soreness:Muscle Soreness:Exercise-Induced Muscle CrampsExercise-Induced Muscle Cramps
• EAMC type 1: muscle overload/fatigue– Excite muscle spindle, inhibit Golgi tendon organ
abnormal -motor neuron control– Localized to overworked muscle– Risks: age, poor stretching, history, high intensity
• EAMC type 2: electrolyte deficits– Excessive sweating Na+, Cl- disturbances– To account for ion loss, fluid shifts– Neuromuscular junction becomes hyperexcitable
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Muscle Soreness:Muscle Soreness:Exercise-Induced Muscle CrampsExercise-Induced Muscle Cramps
• Treatment depends on type of cramp
• Fatigue-related cramps– Rest– Passive stretching
• Electrolyte-related (heat) cramps– Prompt ingestion of high-salt solution, fluids– Massage– Ice