Scientific Principles of Strength Training

8/19/2019 Scientific Principles of Strength Training

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The Scientific Principles of Strength TrainingThe Scientific Princi

ples of Strength Training

Muscular StrengthMuscular Strength: The amount of: The amount offorce a muscle can produce with aforce a muscle can produce with a

single maximal effortsingle maximal effort

Mechanical Strength:Mechanical Strength: the maximumthe maximum

torque that can be generated about atorque that can be generated about a

joint joint


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Torque about the elbow jointTorque about the elbow joint

Strength determined by:

• Absolute force developed by muscle

• Distance from joint center to tendon insertion

• Angle of tendon insertion


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Shoulder joint torque as a function of arm positionShoulder

joint torque as a function of arm position


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Structural organization of skeletal muscleStructural or

ganization of skeletal muscle

rom !rinciples of"uman Anatomy #$th edition%& '(() by*erard +, Tortora& ig

(,)& p -'.


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6-6

rom /asic/iomechanicsby Susan "all#.rd edition%&ig 0,0& page').


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rom S1eletal 2uscle:orm and unction #-nd

ed% by 2ac3ntosh&*ardiner& and 2c4omas,ig ',5& p, 6,


8/386-5

rom /asic /iomechanics by Susan

"all #.rd edition%& ig 0,)& page ')-


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A motor unit: single motor neuron and allthe muscle fibers it innervates

rom /asic /iomechanics3nstructors manual by Susan"all #-nd edition& '(()%& ig T2.'


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rom /asic /iomechanics by Susan"all #.rd edition%& ig 0,$& page')5


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rom /asic /iomechanics by Susan "all#.rd edition%& ig 0,6& page ')5


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Factors affecting force ProductionFactors affecting force Production

', 4ross;sectional', 4ross;sectional

areaarea "ypertrophy: increase"ypertrophy: increasein the ? of myofibrilsin the ? of myofibrils

and myofilamentsand myofilaments

"yperplasia: increase"yperplasia: increasein the number ofin the number of

fibers@@@fibers@@@


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2.2. Rate oding ! frequenc" of stimulationRate oding ! frequenc" of stimulation

rom /asic /iomechanics by Susan "all#.rd edition%& ig 0,(& page '))


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., Spatial recruitment., Spatial recruitment

3ncrease ? of active motor units #2s%3ncrease ? of active motor units #2s%

rder of recruitmentrder of recruitment

3 ;;;B 33a ;;;;;B 33b3 ;;;B 33a ;;;;;B 33b

"ennemanCs sie principle: 2s are recruited in"ennemanCs sie principle: 2s are recruited inorder of their sie& from small to largeorder of their sie& from small to large

Eelative contributions of rate coding and spatialEelative contributions of rate coding and spatialrecruitment,recruitment,• Small muscles ; all 2s recruited at approximately )7=Small muscles ; all 2s recruited at approximately )7=

max, forceF thereafter& rate coding is responsible formax, forceF thereafter& rate coding is responsible forforce increase up to maxforce increase up to max

• Garge muscles ; all 2s recruited at approximately 67=Garge muscles ; all 2s recruited at approximately 67=max, force,max, force,


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The force#$elocit"

relationship formuscle tissue% -s

the load increases)

concentric

contraction $elocit"

slows to zero at

isometric

ma*imum. +elocit"

F o r c

e

isometric

ma*imum


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Force-Velocity Relationship in different muscle fiber typesForce-Velocity Relationship in different muscle fiber types

Type 33 fiber

Type 3 fiber


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Effect of Temperature on Force-Velocity relationshipEffect of Temperature on Force-Velocity relationship(22(22ooC, 25C, 25ooC, 3CC, 3Coo, and 3!, and 3!ooC"C"


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Force -Velocity Relationship (Effect of stren#th-Trainin#"Force -Velocity Relationship (Effect of stren#th-Trainin#"


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Force#$elocit" Relationship uring /ccentricForce#$elocit" Relationship uring /ccentric

0uscular ontractions0uscular ontractions


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Force1+elocit"1Power RelationshipForce1+elocit"1Power Relationship

F o r c e

Velocity

P o

w e

r

.7=

.7=

Force/velocity curve

Power/velocitycurve

rom /asic /iomechanicsby Susan "all #.rdedition%& ig 0,-)& page'$)


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Effect of $uscle Fiber Types on %o&er-Velocity RelationshipEffect of $uscle Fiber Types on %o&er-Velocity Relationship

f h f l i l i hi f

f th f l it l ti hi f


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onsequences of the force#$elocit" relationship foronsequences of the force#$elocit" relationship for

sports practicesports practice

Ihen training for sports that require power& trainIhen training for sports that require power& train

with the appropriate = of ' E2 that will elicit thewith the appropriate = of ' E2 that will elicit themost power,most power,

-5 wee1s of:-5 wee1s of:

a%, heavy weight;training b, 8xplosive strengtha%, heavy weight;training b, 8xplosive strength

trainingtraining

rom Scienceand !racticeof StrengthTraining #-nd edition% H,2,Jatsiors1yand I,+,9raemer#-770% ig-,'( !, .(%


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Ihy do elite weight lifters start a barbell liftIhy do elite weight lifters start a barbell liftfrom the floor slowly@from the floor slowly@

They try to accelerate maximally when the barThey try to accelerate maximally when the baris at 1nee height, Two reasons:is at 1nee height, Two reasons:

', At this position& the highest forces can be', At this position& the highest forces can begenerated as a result of body posturegenerated as a result of body posture


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-, /ecause force-, /ecause force

decreases whendecreases when

velocity increases&velocity increases&barbell mustbarbell must

approach the mostapproach the most

favored position atfavored position at

a relatively lowa relatively lowvelocity to impartvelocity to impart

maximal force tomaximal force to

the bar,the bar,

rom Science and !ractice of StrengthTraining #-nd edition% H,2, Jatsiors1y andI,+, 9raemer #-770% ig -,-7 !, 57%


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-daptations associated with strength training -daptations associated with strength training

',', Activates proteinActivates proteincatabolism, Thiscatabolism, This

creates conditions forcreates conditions for

enhanced synthesis ofenhanced synthesis of

contractile proteinscontractile proteinsduring the rest periodduring the rest period

#brea1 down& build up#brea1 down& build up

theory%theory%

rom E,G, Geiber #'((-%, S1eletal2uscle Structure and unction, ig

0,'& p, -0-,


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-, Keural adaptations occur to improve-, Keural adaptations occur to improve

intra;muscular and inter;muscularintra;muscular and inter;muscular

coordination,coordination,

• 3ntra;muscular coordination < affects the3ntra;muscular coordination < affects the

ability to voluntarily activate individual fibers inability to voluntarily activate individual fibers in

a specific musclea specific muscle

• 3nter;muscular coordination < affects the3nter;muscular coordination < affects the

ability to activate many different muscles atability to activate many different muscles at

the appropriate timethe appropriate time


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3ntra;muscular coordination changes with3ntra;muscular coordination changes with

trainingtraining

ntrained individuals find it difficult tontrained individuals find it difficult torecruit all their fast;twitch 2s, Iithrecruit all their fast;twitch 2s, Iithtraining& an increase in 2 activationtraining& an increase in 2 activationoccursoccurs

Strength training also trains the 2s toStrength training also trains the 2s tofire at the optimal firing rate to achievefire at the optimal firing rate to achievetetanytetany

2s might also become activated more2s might also become activated moresynchronously during all out maximumsynchronously during all out maximumefforteffort


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4onsequently& maximal muscular4onsequently& maximal muscular

force is achieved when:force is achieved when:

',', A maximal ? of both T and ST motorA maximal ? of both T and ST motorunits are recruitedunits are recruited

-, Eate coding is optimal to produce a-, Eate coding is optimal to produce a

fused state of tetanyfused state of tetany

., The 2s wor1 synchronously over the., The 2s wor1 synchronously over the

short period of maximal effort,short period of maximal effort,


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!sychological factors are also of importance!sychological factors are also of importance

4KS either increases the flow of excitatory stimuli& decreases4KS either increases the flow of excitatory stimuli& decreases

inhibitory stimuli& or bothinhibitory stimuli& or both

4onsequently& an expansion of the recruitable motor neuron4onsequently& an expansion of the recruitable motor neuron

pool occurs and an increase in strength resultspool occurs and an increase in strength results

"idden strength potential of human muscle can also be"idden strength potential of human muscle can also bedemonstrated by electrostimulationdemonstrated by electrostimulation

2uscle strength deficit #2SD% L2uscle strength deficit #2SD% L

##orce during electrostimulation;2aximal voluntary forceorce during electrostimulation;2aximal voluntary force% x '77% x '77

2aximal voluntary force2aximal voluntary force

Typically falls between );.)=Typically falls between );.)=

8lectrostimulation8lectrostimulation


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8lectrostimulation8lectrostimulation

• !ossibility exists to induce hypertrophy through!ossibility exists to induce hypertrophy throughelectrostimulationelectrostimulation

• "owever& does not train the nervous system to"owever& does not train the nervous system torecruit motor unitsrecruit motor units

/ilateral Deficit/ilateral Deficit

• During maximal contractions& the sum of forcesDuring maximal contractions& the sum of forcesexerted by homonymous muscles unilaterally isexerted by homonymous muscles unilaterally istypically larger than the sum of forces exerted by thetypically larger than the sum of forces exerted by the

same muscles bilaterallysame muscles bilaterally

• /ilateral training can eliminate this deficit& or even/ilateral training can eliminate this deficit& or evenallow bilateral facilitationallow bilateral facilitation


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ther benefits of strength trainingther benefits of strength training 3ncrease in resting metabolic rate3ncrease in resting metabolic rate

• 8ach additional pound of muscle tissue increases8ach additional pound of muscle tissue increasesresting metabolism by .7 to )7 calories per day L '7&()7resting metabolism by .7 to )7 calories per day L '7&()7to '6&-)7 calories a year L .;) lb of fatto '6&-)7 calories a year L .;) lb of fat

3ncrease in bone mineral content and& therefore& bone density3ncrease in bone mineral content and& therefore& bone density

3ncreases the thic1ness and strength of the connective tissue3ncreases the thic1ness and strength of the connective tissuestructures crossing joints such as tendons and ligaments


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0etabolic stress of resistance0etabolic stress of resistance

trainingtraining 4lassed as only light to moderate in terms4lassed as only light to moderate in terms

of energy expenditure per wor1outof energy expenditure per wor1out

Standard weight;training does not improveStandard weight;training does not improveendurance or produce significantendurance or produce significant

cardiovascular benefits li1e aerobic typecardiovascular benefits li1e aerobic type

activity doesactivity does

4ircuit;training increases metabolic stress4ircuit;training increases metabolic stress


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Delayed onset of muscle sorenessDelayed onset of muscle soreness

#D2S%#D2S%

The intensity and the novelty of a wor1out influence how sore youThe intensity and the novelty of a wor1out influence how sore youbecomebecome

Gactate does not cause muscle soreness due to:Gactate does not cause muscle soreness due to:

• ', Gactate returns to baseline within an hour of exercise', Gactate returns to baseline within an hour of exercise• -, After exercise& lactate is in equal amounts within the muscle-, After exercise& lactate is in equal amounts within the muscle

and the bloodand the blood• ., D2S is specific& not generalied., D2S is specific& not generalied

2uscle soreness is due to the physiological response to muscle2uscle soreness is due to the physiological response to musclefiber and connective tissue damage #microtears%fiber and connective tissue damage #microtears%

Ihite blood cells enter the muscle tissue& clean up the debris ofIhite blood cells enter the muscle tissue& clean up the debris ofbro1en proteins& and then initiate the regeneration phasebro1en proteins& and then initiate the regeneration phase


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0uscle Soreness 'continued(0uscle Soreness 'continued(

8dema #increase in fluid% to the area accompanies8dema #increase in fluid% to the area accompanies

the above responsethe above response

The pressure from edema is thought to produceThe pressure from edema is thought to producethe sensation of sorenessthe sensation of soreness

Also& metabolic by;products released from theAlso& metabolic by;products released from the

macrophages may sensitie pain receptorsmacrophages may sensitie pain receptors

Kext stage is the proliferation of satellite cells ;Kext stage is the proliferation of satellite cells ;

help form new myofibrilshelp form new myofibrils

8ccentric contractions cause the greatest amount8ccentric contractions cause the greatest amountof sorenessof soreness

Scientific Principles of Strength Training

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