Chapter 13Chapter 13The Physiology of Training:The Physiology of Training:Muscular StrengthMuscular StrengthPrinciples of TrainingPrinciples of TrainingOverloadOverload––Training effect occurs when a system is Training effect occurs when a system is exercised at a level beyond which it is exercised at a level beyond which it is normally accustomednormally accustomedSpecificitySpecificity––Training effect is specific to the muscle Training effect is specific to the muscle fibers involvedfibers involved––Type of exerciseType of exerciseReversibilityReversibility––Gains are lost when overload is removedGains are lost when overload is removedResearch Designs to Research Designs to Study TrainingStudy TrainingCrossCross--sectional sectional studiesstudies––Examine groups of Examine groups of differing physical differing physical activity at one timeactivity at one time––Record differences Record differences between groupsbetween groupsLongitudinal Longitudinal studiesstudies––Examine groups Examine groups before and after before and after trainingtraining––Record changes Record changes over time in the over time in the groupsgroupsPhysiological Effects of Strength Physiological Effects of Strength TrainingTrainingResistance training can result in increased Resistance training can result in increased muscle size and strengthmuscle size and strengthResistance training can result in an Resistance training can result in an increase in muscle enduranceincrease in muscle enduranceStimulus for GainsStimulus for GainsTheoryTheory––Changes in CNS may be responsibleChanges in CNS may be responsibleStrength and enduranceStrength and endurance––CNS may inhibit strength/enduranceCNS may inhibit strength/enduranceCNS changes through trainingCNS changes through training––This allows more motor units to be activatedThis allows more motor units to be activated––GTO and MS desensitized with trainingGTO and MS desensitized with trainingPhysiological Effects of Strength Physiological Effects of Strength TrainingTrainingNeural factorsNeural factors––Increased ability to activate motor unitsIncreased ability to activate motor units––CoordinationCoordination––Increased ability to recruit prime moversIncreased ability to recruit prime movers––Strength gains in initial 8Strength gains in initial 8--20 weeks20 weeksMuscular enlargement (delayed)Muscular enlargement (delayed)––Mainly due enlargement of fibers Mainly due enlargement of fibers (hypertrophy)(hypertrophy)––LongLong--term strength training requiredterm strength training requiredNeural and Muscular Adaptations Neural and Muscular Adaptations to Resistance Training to Resistance Training Fig 13.17Training AdaptationsTraining AdaptationsBiochemical and fiber composition Biochemical and fiber composition changes:changes:––Increases in creatine, PC, ATP, glycogenIncreases in creatine, PC, ATP, glycogen––Increase or little change in glycolytic enzymesIncrease or little change in glycolytic enzymes––Small increases in Krebs Cycle enzymesSmall increases in Krebs Cycle enzymes––Decrease in volume or density of Decrease in volume or density of mitochondria due to increase in size of mitochondria due to increase in size of myofibrils and myofibrils and sarcoplasmicsarcoplasmicvolumevolumeTraining Adaptations (cont)Training Adaptations (cont)In generalIn general––Biochemical changes are small and Biochemical changes are small and inconsistentinconsistent––High % FT fibers are prerequisite for maximal High % FT fibers are prerequisite for maximal strength gainsstrength gainsStrength GainsStrength GainsStrength is a property of the motor systemStrength is a property of the motor systemStrength can be gained without structural Strength can be gained without structural changes in musclechanges in muscle––Strength not only a property of muscleStrength not only a property of muscleStrength cannot be gained without neural Strength cannot be gained without neural adaptations.adaptations.––Motor unit recruitment may explain some of Motor unit recruitment may explain some of the strength increase with lack of hypertrophythe strength increase with lack of hypertrophyTraining to Improve Training to Improve Muscular StrengthMuscular StrengthStrengthStrength--training exercisestraining exercises––Isometric or staticIsometric or static––Dynamic or isotonicDynamic or isotonicIncludes variable resistance exerciseIncludes variable resistance exercise––IsokineticIsokineticMuscle contracts at constant speedMuscle contracts at constant speedMachine adjusts to maintain load through contractionMachine adjusts to maintain load through contractionFastest method to gain strengthFastest method to gain strengthIncrease in muscle sizeIncrease in muscle size––Due to hypertrophy (Due to hypertrophy (↑↑fiber diameter)fiber diameter)––Due to hyperplasia? (Due to hyperplasia? (↑↑fiber number)fiber number)Progressive Resistance Progressive Resistance ExerciseExerciseImprovements in strength via progressive Improvements in strength via progressive overloadoverload––Periodically increasing resistance (weight Periodically increasing resistance (weight lifted) to continue to overload the musclelifted) to continue to overload the muscleBasis for most weightBasis for most weight--training programstraining programsPrinciples of Strength TrainingPrinciples of Strength TrainingMuscles must be exercised near peak Muscles must be exercised near peak tension for increases in strengthtension for increases in strengthThere is no There is no ““optimumoptimum””training programtraining program––33--4 days per week with rest days in between 4 days per week with rest days in between is recommendedis recommendedStrength training should involve the same Strength training should involve the same muscles as competitionmuscles as competition––Movement pattern, speed of shortening Movement pattern, speed of shorteningFree Weights vs. MachinesFree Weights vs. MachinesStrength gains are similar following Strength gains are similar following training using free weights and machinestraining using free weights and machinesArgument for free weights:Argument for free weights:––Data exist showing that free weights produce Data exist showing that free weights produce greater strength gainsgreater strength gains––Free weights produce greater movement Free weights