aging and the effects of exercise on muscle mass and function stephen p. sayers, phd, department of...

Aging and the effects of Aging and the effects of exercise on muscle mass and exercise on muscle mass and

functionfunction

Stephen P. Sayers, PhD, Department Stephen P. Sayers, PhD, Department of Physical Therapy, University of of Physical Therapy, University of

MissouriMissouri

I. Changes in Muscle Mass with AgingI. Changes in Muscle Mass with Aging

II. Changes in Muscle Performance with II. Changes in Muscle Performance with AgingAging

IV. Does Exercise Restore Muscle Mass and IV. Does Exercise Restore Muscle Mass and Function?Function?

III. Factors Responsible for Age-Related III. Factors Responsible for Age-Related Changes in Muscle Mass and FunctionChanges in Muscle Mass and Function

Outline

SarcopeniaSarcopenia

Strength, PowerStrength, Power

Changes in Muscle Mass with AgingChanges in Muscle Mass with Aging

40% loss in muscle mass from 20-70 years of age

Rogers & Evans, 1993

6% decline in muscle mass per decade from age 30-70

Fleg & Lakatta, 1988

1.4 –2.5% decline in muscle mass per year after age 60

Frontera et al., 2000

Changes in Muscle Mass with AgingChanges in Muscle Mass with Aging

Lexell et al., 1988


• ““Sarco” flesh (muscle).Sarco” flesh (muscle).• ““penia” deficiency.penia” deficiency.• Sarcopenia is associated with increased Sarcopenia is associated with increased

mortality and functional declinemortality and functional decline

Roubenoff, 2003Roubenoff, 2003

age-associated decline in muscle massage-associated decline in muscle mass


21 year old Female (BMI = 24.3 kg/m21 year old Female (BMI = 24.3 kg/m22))

73 year old Female (BMI = 24.5 kg/m73 year old Female (BMI = 24.5 kg/m22))


SarcopeniaSarcopeniaMuscle Fiber Changes with Aging: Muscle Fiber Changes with Aging:

1)1) Decreased muscle fiber size Decreased muscle fiber size (atrophy)(atrophy)

2) Decreased number of muscle fibers 2) Decreased number of muscle fibers

SarcopeniaSarcopeniaMuscle Fiber Changes with Aging:Muscle Fiber Changes with Aging:1) Atrophy1) Atrophy

Men: 20-29 and 60-65Men: 20-29 and 60-65Type I - no changeType I - no changeType II - 25% decreaseType II - 25% decrease

Men: 19-84Men: 19-84Type I - 6% decreaseType I - 6% decreaseType II - 35% decreaseType II - 35% decrease

Larsson et al., 1978Larsson et al., 1978

Lexell, 1991Lexell, 1991

Muscle Fiber Changes with Aging:Muscle Fiber Changes with Aging:

1)1) AtrophyAtrophy

By age 85, Type II fiber CSA may be less By age 85, Type II fiber CSA may be less than 50% of that for Type I fibersthan 50% of that for Type I fibers


Type IType I

Type IIType II


1)1) AtrophyAtrophy

Maintenance of Type I fiber size may be Maintenance of Type I fiber size may be compensatory hypertrophycompensatory hypertrophy

Lexell, 1991Lexell, 1991

Disuse of Type II fibers?Disuse of Type II fibers?




2) Decreased number of fibers2) Decreased number of fibers

25% loss in men ages 19-37 to 70-73 25% loss in men ages 19-37 to 70-73 (110,000 difference)(110,000 difference)

Muscle of 20 yr old - 70% fibers Muscle of 20 yr old - 70% fibers

Muscle of 80 yr old - 50% fibersMuscle of 80 yr old - 50% fibers

Lexell et al., 1983Lexell et al., 1983

Lexell et al., 1988Lexell et al., 1988

SarcopeniaSarcopeniaMuscle Fiber Changes with Aging:Muscle Fiber Changes with Aging:

2) Decreased number of fibers2) Decreased number of fibers

Selective loss of Type II fibers:Selective loss of Type II fibers:

Type I fiber % increased from 40 to 55 Type I fiber % increased from 40 to 55 in men ages 20-30 and 60-65in men ages 20-30 and 60-65

Larsson, 1982Larsson, 1982

• • Loss of Type II fibers?Loss of Type II fibers?

•• Acquiring more Type I fibers? Acquiring more Type I fibers?


““No single feature of age-related No single feature of age-related decline can more dramatically decline can more dramatically affect nutritional status, affect nutritional status, ambulation, mobility, and ambulation, mobility, and functional independence.”*functional independence.”*

*Rosenberg 1989*Rosenberg 1989

Prevalence (%) of Sarcopenia*Prevalence (%) of Sarcopenia*

43.243.252.652.6>80>80

35.935.926.726.775 – 8075 – 80

33.333.319.819.870 – 7470 – 74

23.123.113.513.5<70<70

FemalesFemales(n=173)(n=173)

MalesMales(n=205)(n=205)

Age groupAge group(years)(years)

*New Mexico Elder Health Survey, Baumgartner et al. 1998*New Mexico Elder Health Survey, Baumgartner et al. 1998

II. Changes in Muscle Performance II. Changes in Muscle Performance with Agingwith Aging

Muscle StrengthMuscle Strength

• Maximum capacity to generate Maximum capacity to generate forceforce or tension. or tension.

• Muscle CSAMuscle CSA• Intrinsic factorsIntrinsic factors• MU recruitment / Firing rateMU recruitment / Firing rate

Upper extremity strengthUpper extremity strength

0

20

40

60

80

100

120

25 35 45 55 65 75 85

Strength

AgeAge

% of 20 yr % of 20 yr old groupold group

Metter et al., 1997Metter et al., 1997J. Gerontol.J. Gerontol.

8% loss per decade after age 45 - 8% loss per decade after age 45 -

Brooks, 1995Brooks, 1995

Strength increases up to age 30Strength increases up to age 30

Plateaus from age 30 – 50Plateaus from age 30 – 50

Declines 24-36% between 50-70Declines 24-36% between 50-70Larsson, 1979Larsson, 1979

Strength Loss with AgingStrength Loss with Aging

# women unable to life 4.5 kg (10 lbs) # women unable to life 4.5 kg (10 lbs) increased from 40% in 55-64 yr olds to 65% increased from 40% in 55-64 yr olds to 65% in those age 75-84.in those age 75-84.

Jette & Branch, 1981Jette & Branch, 1981

15% loss per decade up to 615% loss per decade up to 6thth and 7 and 7thth decades of life, 30% loss per decade decades of life, 30% loss per decade thereafterthereafter Evans, 1997Evans, 1997

Strength Loss with AgingStrength Loss with Aging

35% loss over 11 year period in 80 35% loss over 11 year period in 80 year old subjectsyear old subjects

Grabiner & Enoka 1995Grabiner & Enoka 1995

Most precipitous loss after age 70:Most precipitous loss after age 70:

Strength loss does not always Strength loss does not always parallel loss in muscle massparallel loss in muscle mass

• Specific Strength Specific Strength (Force per CSA)(Force per CSA) may be lower in older compared to younger men may be lower in older compared to younger men

• Quadriceps CSA decreased 21% (65-80)Quadriceps CSA decreased 21% (65-80)• Force production decreased 39%Force production decreased 39%

Jubrias et al. (1997)Jubrias et al. (1997)

• Quantitative and qualitative changesQuantitative and qualitative changes

Muscle PowerMuscle Power

• Power:Power: Maximum rate of work performance Maximum rate of work performance

Power = Force x VelocityPower = Force x Velocity

Power vs. strength over timePower vs. strength over time

0

20

40

60

80

100

120

25 35 45 55 65 75 85

StrengthPower

AgeAge

% of 20 yr % of 20 yr old groupold group

Metter et al., 1997Metter et al., 1997J. Gerontol.J. Gerontol.

Muscle PowerMuscle Power• Men and women in their 70s compared to 20s:Men and women in their 70s compared to 20s:

Vertical JumpVertical Jump Force 50% lower Force 50% lower

Vertical Jump Power 70-75% lowerVertical Jump Power 70-75% lower

Bosco & Komi, 1980Bosco & Komi, 1980

• Strength loss 1-2% per year after 60Strength loss 1-2% per year after 60

• Power loss is ~3.5% per yearPower loss is ~3.5% per year

Skelton et al., 1994Skelton et al., 1994

% MVC/Power needed % MVC/Power needed to perform ADLsto perform ADLs

How do changes in strength and How do changes in strength and power impact function?power impact function?

0102030405060708090

100

Percentage of Maximum voluntary

contraction(MVC)

25 years 75 years

MVC

*Diminished reserve capacity*Diminished reserve capacity

III. Factors Responsible for III. Factors Responsible for Age-Related Changes in Age-Related Changes in Muscle Mass and FunctionMuscle Mass and Function

SarcopeniaSarcopenia**

• etiology related to changes in: etiology related to changes in:

hormone statushormone status

neural factors neural factors

Inflammation Inflammation

protein/energy intake protein/energy intake

disuse atrophydisuse atrophy

*Rosenberg 1989*Rosenberg 1989


Age-relatedAge-related

BehavioralBehavioral


Roubenoff, 2003Roubenoff, 2003

1.1. Changes in force producing capability Changes in force producing capability of muscle tissueof muscle tissue

2.2. Changes in neural activation of Changes in neural activation of musclesmuscles

What factors are responsible for What factors are responsible for decreased strength in older men and decreased strength in older men and women?women?

1.Changes in force producing capabilities 1.Changes in force producing capabilities of muscleof muscle

1.Decrease In 1.Decrease In Specific Tension of Specific Tension of

Individual FibersIndividual Fibers

3. Muscle Atrophy3. Muscle Atrophy

Death of Death of –motor –motor neurons neurons

(spinal cord)(spinal cord)

Death of Some Death of Some Muscle FibersMuscle Fibers

Barry & Carson, J Gerontol 2004

2. Relative Increase in 2. Relative Increase in Type I Type I

Fiber CharacteristicsFiber Characteristics

-Re-innervation of -Re-innervation of Some fibersSome fibers

-Motor Unit Remodeling-Motor Unit Remodeling(Fewer, larger MUs)(Fewer, larger MUs)

-Multiple MHC isoforms-Multiple MHC isoforms(hormones)(hormones)

““The ability to develop maximal The ability to develop maximal force… is dependent upon the force… is dependent upon the capacity of the nervous system to capacity of the nervous system to maximally maximally activate individual musclesactivate individual muscles, , and to and to coordinate coordinate appropriately the appropriately the activation of groups of muscles.”activation of groups of muscles.”

Barry & Carson, J Gerontol 2004Barry & Carson, J Gerontol 2004

2. Changes in neural activation of 2. Changes in neural activation of musclesmuscles

2. Changes in neural activation of 2. Changes in neural activation of musclesmuscles

1.Inability to maximally 1.Inability to maximally activate individualactivate individual

musclesmuscles

••Reduced cortical driveReduced cortical drive••Altered Altered –motor neuron excitability–motor neuron excitability

••NMJ DegradationNMJ Degradation ••Impaired E-C CouplingImpaired E-C Coupling

2. Inability to coordinate2. Inability to coordinategroups of musclesgroups of muscles

••Increased co-activation of Increased co-activation of agonist/antagonistagonist/antagonist

••Increased antagonist activationIncreased antagonist activation

Reduces net maximal Reduces net maximal joint torquejoint torque

Limits rate of force Limits rate of force developmentdevelopment

••Distrupted agonist/synergistDistrupted agonist/synergistactivationactivation

Barry & Carson, J Gerontol 2004Barry & Carson, J Gerontol 2004

Skeletal muscle massSkeletal muscle mass““Sarcopenia”Sarcopenia” Neural FactorsNeural Factors

Fiber number,Cross-sectional area,

Selective type II atrophyLarsson, 1979

Specific tension,in vitro shortening velocity

Larsson, 1997Reduced MU firing rates,Reduced MU firing rates,Asynchronous MU firing,Asynchronous MU firing,

Slowed nerve CVSlowed nerve CV

Loss of Motor unitsLoss of Motor units(47% decrease 20-65)(47% decrease 20-65)

Doherty, 1993Doherty, 1993MU remodeling (Type I)MU remodeling (Type I)

Contraction velocity:E-C coupling impairment

SR impairmentActin slowing (18-25%)

Factors responsible for decreases in powerFactors responsible for decreases in power

IV. Does Exercise Restore Muscle IV. Does Exercise Restore Muscle Mass and Function?Mass and Function?

Muscle and Neural Adaptations Muscle and Neural Adaptations with Resistance Trainingwith Resistance Training

Resistance Training in Older AdultsResistance Training in Older Adults

• Landmark RT Studies:Landmark RT Studies:Moritani & DeVries (1980) Moritani & DeVries (1980) Aniansson et al. (1980)Aniansson et al. (1980)

First studies to demonstrate safety and First studies to demonstrate safety and potential for increases in strength in older potential for increases in strength in older menmen

Little hypertrophy responseLittle hypertrophy response

• Landmark Studies:Landmark Studies:

Resistance training and strength:Resistance training and strength:

Men 60-72 (12 weeks): 107-226% increaseMen 60-72 (12 weeks): 107-226% increaseFrontera et al., 1988Frontera et al., 1988

Women 64-86 (12 weeks): 28-115% Women 64-86 (12 weeks): 28-115% increaseincrease

Charette et al., 1991Charette et al., 1991

Men & Women 86-96 (8 weeks): 174% Men & Women 86-96 (8 weeks): 174% increase increase

Fiatarone et al., 1990Fiatarone et al., 1990


• Landmark Studies

Resistance training and hypertrophy: Men 60-72 (12 weeks): Type I – 33.5% increase

Type II – 27.6% increase Frontera et al., 1988

Women 64-86 (12 weeks): Type I – 7.3% increase (NS) Type II – 20% increase Charette et a., 1991

Men & Women 86-96 (8 weeks): Muscle CSA (8.4-11%) Fiatarone et al., 1990


Power Training in Older AdultsPower Training in Older Adults

Fielding et al. (2002)Fielding et al. (2002)

Power training in older women Power training in older women (N=25; Age = 73.2 (N=25; Age = 73.2 years)years)

Power Training: Power Training: High-intensity high High-intensity high velocity RTvelocity RT

Strength Training: Strength Training: High-intensity low High-intensity low velocity RTvelocity RT

LP and KE: 3 x 8, 3x/wk, 16-wks @ 70% 1RMLP and KE: 3 x 8, 3x/wk, 16-wks @ 70% 1RM

The Disablement Pathway The Disablement Pathway (Nagi, 1965; Verbrugge & Jette, 1994)(Nagi, 1965; Verbrugge & Jette, 1994)

PathologyPathology

ImpairmentImpairment

Functional Functional LimitationLimitation

DisabilityDisability

StrengthStrength

PowerPower

??

??

Resistance Training in Older Resistance Training in Older AdultsAdults

• Effects on Function and Disability are Effects on Function and Disability are Questionable:Questionable:

Latham et al., 2003Latham et al., 2003

Small to moderate effect on FunctionSmall to moderate effect on Function

Little to no effect on Physical DisabilityLittle to no effect on Physical Disability

Functional Threshold

Threshold

Functionally Limited (Frail)

Healthy Elderly

Motor Impaired “Pre-Frail”

Function

Strength/Power


Pathology

Impairment

Functional Limitation

Disability

Correcting “strength” Correcting “strength” impairments has been impairments has been primary focusprimary focus

What about other What about other impairments?impairments?

Muscle PowerMuscle Power

Key component of success in athleticsKey component of success in athletics

• Maximum rate of work performanceMaximum rate of work performance

Power = F x VPower = F x V

Is Muscle Power and Contraction Is Muscle Power and Contraction Velocity Important in Older Adults?Velocity Important in Older Adults?

Muscle Power and FunctionMuscle Power and Function

Bean et al.,Bean et al., 2002; Suzuki et al., 2001; 2002; Suzuki et al., 2001; Foldvari et al., 2000Foldvari et al., 2000

Studies have shown that lower extremity Studies have shown that lower extremity muscle power is a stronger predictor of muscle power is a stronger predictor of functional limitations and disability than functional limitations and disability than muscle strength in older men and womenmuscle strength in older men and women

Muscle power declines sooner and more Muscle power declines sooner and more rapidly than strengthrapidly than strength

Pathology

Impairment


Disability

*Power may be a more *Power may be a more critical variable on critical variable on which to focus which to focus resistance training resistance training protocolsprotocols


Low and High Velocity Power and Low and High Velocity Power and FunctionFunction

Physical Performance Coefficient Standard Error R2 p-value Stair Climb (n=45) 1RM strength -0.270 0.12 0.32 0.027 Leg Power* 70% 1RM -0.206 0.071 0.43 0.000

40% 1RM -0.169 0.06 0.42 0.000 Chair Rise (n=45) 1RM strength -0.301 0.10 0.31 0.005 Leg Power* 70% 1RM -0.152 0.070 0.24 0.024 40% 1RM -0.154 0.057 0.28 0.009 Habitual Gait (n=45) 1RM strength 0.296 0.08 0.40 0.001 Leg Power*

70% 1RM 0.223 0.049 0.51 0.000 40% 1RM 0.214 0.037 0.59 0.000 *adjusted for age, body mass, and gender

Muscle power at Muscle power at high or low high or low velocity may be velocity may be more important more important to certain to certain functional tasks functional tasks than muscle than muscle strengthstrength

Cuoco A, Callahan DM, Sayers SP, et al. J. Am. Geriatr. Soc. 2004

Speed at which Speed at which we generate we generate power is critical power is critical to lower to lower intensity intensity functional tasksfunctional tasks

Contraction Velocity and FunctionContraction Velocity and Function________________________________________________________________________ Function Standardized p-value Partial F Partial R2 VIF Gait Speed over 400 m ALL; n=101 Model R2=0.32 (p<0.001) Velocity (m/s) 0.483 <0.001 24.5 0.18 1.304 Leg Strength (N) 0.296 0.005 8.18 0.06 1.471 Sex -0.247 0.020 5.61 0.04 1.494 Women; n=64 Model R2=0.24 (p<0.001) Velocity (m/s) 0.485 <0.001 17.8 0.24 1.000 Leg Strength (N)* Men; n=37 Model R2=0.39 (p<0.001) Velocity (m/s) 0.420 0.005 9.03 0.16 1.087 Leg Strength (N) 0.356 0.016 6.49 0.12 1.087

Contraction Contraction velocity alone velocity alone was more was more important to important to walking walking speed than speed than muscle muscle strength in strength in older adultsolder adults

Sayers SP, et al. J. Am. Geriatr. Soc. 2005

Pathology

Impairment


Disability

*Contraction velocity *Contraction velocity (speed)(speed) may also be a may also be a critical variable on critical variable on which to focus which to focus resistance training resistance training protocolsprotocols


Current Study - SayersCurrent Study - Sayers

5353 (12 currently)(12 currently) older men and women > 65 years of age older men and women > 65 years of age

will perform 12 weeks of RT 3x/weekwill perform 12 weeks of RT 3x/week

Velocity TrainingVelocity Training: 3 x 14 @40% 1RM "as fast as possible": 3 x 14 @40% 1RM "as fast as possible"

Strength Training:Strength Training: 3 x 8 @80% 1RM over 2 seconds 3 x 8 @80% 1RM over 2 seconds

ControlControl

Functional Tasks: Functional Tasks: Stair Climb, Chair rise, Timed Up and Go, Stair Climb, Chair rise, Timed Up and Go, Balance, Short and long walking tasksBalance, Short and long walking tasks

Preliminary ConclusionsPreliminary Conclusions

• Muscle strength and power both appear to be Muscle strength and power both appear to be improved with velocity trainingimproved with velocity training

• Some functional tasks appear to be improved by Some functional tasks appear to be improved by training at lower resistances and higher speedstraining at lower resistances and higher speeds

• Too soon to tellToo soon to tell

aging and the effects of exercise on muscle mass and function stephen p. sayers, phd, department of...

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