muscle mass and strength
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Muscle mass and strength. Muscle mass is the primary determinant of strength Obese individuals have higher lean mass therefore are stronger than thinner people Men have proportionally more lean than women thus are stronger at the same weight - PowerPoint PPT PresentationTRANSCRIPT
Muscle mass and strengthMuscle mass and strength
Muscle mass is the primary determinant Muscle mass is the primary determinant of strengthof strength– Obese individuals have higher lean mass Obese individuals have higher lean mass
therefore are stronger than thinner peopletherefore are stronger than thinner people– Men have proportionally more lean than Men have proportionally more lean than
women thus are stronger at the same weightwomen thus are stronger at the same weight– Sarcopenia, the loss of muscle mass is the Sarcopenia, the loss of muscle mass is the
major determinant of the loss of strength major determinant of the loss of strength with age.with age.
Muscle strength across the lifespanMuscle strength across the lifespan
Strength declines across age groups 70-79Strength declines across age groups 70-79 Health ABC Health ABC
0
20
40
60
80
100
120
140
160
70 72 74 76 78 80
MenWomen
Torque (Nm)
Age
Changes in muscle with ageChanges in muscle with age
Loss of muscle fibersLoss of muscle fibers Loss of motor neurons at the spinal cord Loss of motor neurons at the spinal cord
levellevel Reduction in type II fibers from 60% to Reduction in type II fibers from 60% to
30%30% Increased infiltration of muscle with fatIncreased infiltration of muscle with fat
Changes in muscle metabolism Changes in muscle metabolism with agewith age
Increase in mitochondrial DNA mutationIncrease in mitochondrial DNA mutation Decline in muscle mitochondrial protein Decline in muscle mitochondrial protein
synthesis (40%)synthesis (40%)– Decreased oxidative phosphorylation and Decreased oxidative phosphorylation and
ATP generationATP generation– Results in fatigabilityResults in fatigability
Decline in myosin heavy chain synthesisDecline in myosin heavy chain synthesis– Major protein involved in ATP and conversion Major protein involved in ATP and conversion
of chemical to mechanical energyof chemical to mechanical energy
Sarcopenia: What is driving the Sarcopenia: What is driving the process?process?
Chronic inflammation?Chronic inflammation?– Acute inflammation: anorexic - catabolic stateAcute inflammation: anorexic - catabolic state– Relationship to cancer and cardiac cachexia?Relationship to cancer and cardiac cachexia?
Decline in anabolic hormones?Decline in anabolic hormones?– GH/IGF-1GH/IGF-1– Decline in sex steroid hormonesDecline in sex steroid hormones
Free testosteroneFree testosterone DHEADHEA
– Fading effectiveness of insulinFading effectiveness of insulin Loss of innervation?Loss of innervation?
Muscle Quality – Loss of strength greater Muscle Quality – Loss of strength greater than loss in muscle mass (Health ABC)than loss in muscle mass (Health ABC)
0
4
8
12
16
70 72 74 76 78 80
MenWomen
Nm of torqueper cm2 muscle area
Age
Muscle qualityMuscle quality
Lean mass/muscle Strength Function
Fat mass
+ ?_
Skeletal Muscle fat
Less More Most
Histochemical Staining of Neutral Fat Content Histochemical Staining of Neutral Fat Content within Skeletal Muscle Fiberswithin Skeletal Muscle Fibers
60
80
100
120
140
160
180
Mid
-th
igh
CS
A (
cm2)
25
30
35
40
45
50
Mid
-th
igh
att
enu
atio
n (
HU
)
<71 71-72 73-74 75-76 77-78 79-80
Age (y)
<71 71-7273-74 75-76 77-78 79-80
Age (y)
MenWomen
Muscle area and attenuation are both Muscle area and attenuation are both inversely associated with age: The Health inversely associated with age: The Health
ABC StudyABC Study
Goodpaster, BH. J Appl Physiol 2001;90:2157-2165.
What About the Quality of Muscle?What About the Quality of Muscle?
0.7
0.8
0.9
1.0
1.1
1.2
1.3
Sp
ecif
ic f
orce
(N
m•c
m-2
)
< 30.9 31.0-35.5 35.6-40. > 40.4
Muscle Attenuation (HU)
MenWomen
MenWomen
““Metabolic Obesity”Metabolic Obesity”Intermuscular fat and Visceral fat:Intermuscular fat and Visceral fat:
Associations with Fasting Insulin by BMI strataAssociations with Fasting Insulin by BMI strata
00,05
0,10,15
0,20,25
0,30,35
T1 T2 T3
Intermuscular Thigh FatVisceral Abdominal Fat
00,05
0,10,15
0,20,25
0,30,35
T1 T2 T3
Intermuscular Thigh FatVisceral Abdominal Fat
BMIBMI BMIBMI
SSttaannddaarrddiizzeedd
bbeettaa
0
1
2
3
4
5
6
low medium high
highmedium
low
Lo
wer
-ext
rem
ity
per
form
ance
**
*
*
*
*
Tertilesof totalbody fat
Tertiles of mid-thigh muscle area
Lower extremity function is worse with higher fat and lower muscle area – Health ABC
Visser M, et al, JAGS, in press
*P<0.01
What is the prevalence of What is the prevalence of sarcopenia?sarcopenia?
No standardized definition to define an No standardized definition to define an individual as sarcopenicindividual as sarcopenic
Several proposed methodsSeveral proposed methods– Lean massLean mass– Lean mass relative to healthy young adultLean mass relative to healthy young adult– Lean mass adjusted for height or height Lean mass adjusted for height or height
squaredsquared– Lean/fat ratioLean/fat ratio– Lean for fat mass and heightLean for fat mass and height
Prevalence of sarcopenia and sarcopenic Prevalence of sarcopenia and sarcopenic obesity in Health ABC - lean mass obesity in Health ABC - lean mass adjusted for height and fat massadjusted for height and fat mass
Figure 2b. Prevalence of obesity(BMI>median BMI by gender), Sarcopenia (Residuals<20th percentile), and Sarcopenic-Obesity by Gender
42.941.7
37.038.3
13.011.7
7.08.4
0.0
10.0
20.0
30.0
40.0
50.0
60.0
Men Women
Pre
vale
nce
(P
erce
nt)
obese
normal
sarcopenic
sarcopenic-obese
Risk factors for SarcopeniaRisk factors for Sarcopenia
Likely multifactorial and complexLikely multifactorial and complex– Both behavioral and biological factors probably Both behavioral and biological factors probably
importantimportant
Few identifiedFew identified– New Mexico Elder Health Survey:New Mexico Elder Health Survey:
Age, income, low activity, smoking, lung disease Age, income, low activity, smoking, lung disease (Baumgartner, 1998)(Baumgartner, 1998)
Higher SHBG ( Baumgartner, 2001)Higher SHBG ( Baumgartner, 2001)
– Health ABC:Health ABC: Age, physical activity, smoking; in men, cancer and Age, physical activity, smoking; in men, cancer and
number of chronic conditionsnumber of chronic conditions
Prevention approachesPrevention approaches
Maintain or increase lean massMaintain or increase lean mass– Avoid weight lossAvoid weight loss– Anabolic hormones (GH - IGF-1, Testosterone, Anabolic hormones (GH - IGF-1, Testosterone,
DHEA’s)DHEA’s)– Block cytokines (TNF alpha, Il-6?)Block cytokines (TNF alpha, Il-6?)– Nutritional approaches - ranging from creatine to Nutritional approaches - ranging from creatine to
caloric restrictioncaloric restriction Maintain or increase muscle qualityMaintain or increase muscle quality
– Improve metabolic capacity of muscleImprove metabolic capacity of muscle– Decrease loss of type 2 fibersDecrease loss of type 2 fibers– Strength trainingStrength training
Clinical trials to prevent sarcopeniaClinical trials to prevent sarcopenia
Testosterone, DHEATestosterone, DHEA– Both result in very small increases in lean Both result in very small increases in lean
mass and strength with side effects limiting mass and strength with side effects limiting useuse
GH, GH secretagoguesGH, GH secretagogues– Slight increase in mass without increase in Slight increase in mass without increase in
strengthstrength ExerciseExercise
– Minimal increase in mass, but large increase Minimal increase in mass, but large increase in strengthin strength
The role of exercise in the The role of exercise in the prevention of sarcopeniaprevention of sarcopenia
Frontera et al. J. Appl. Physiol., 1988
05
101520253035404550
Flexion
Extension
Kn
ee S
tren
gth
(kg)
0 12
Weeks of Resistance Training
100
110
120
130
140
150pre
post
Are
a (c
m2 )
Right Left
Lessons from observations of regarding Lessons from observations of regarding sarcopenia and muscle qualitysarcopenia and muscle quality
Preserving lean mass is likely the Preserving lean mass is likely the major key to preserving strengthmajor key to preserving strength
The quality of the muscle is also The quality of the muscle is also important - fat infiltration impairs important - fat infiltration impairs muscle qualitymuscle quality
Both quantity and quality are important Both quantity and quality are important targets for the preservation of function targets for the preservation of function in older agein older age
ConclusionsConclusions Methodologic advances in the ability to quantify Methodologic advances in the ability to quantify
muscle mass and fat distribution have been key muscle mass and fat distribution have been key to progressto progress
More work is now needed to determine risk More work is now needed to determine risk factorsfactors
Preventive interventions will be depend in part Preventive interventions will be depend in part on these findingson these findings
Current strategiesCurrent strategies– Avoid weight lossAvoid weight loss– ExerciseExercise
EndEnd
Anne B. Newman, MD, MPH Anne B. Newman, MD, MPH Sarcopenia in Older AdultsSarcopenia in Older Adults August 19thAugust 19th University of Pittsburgh School of University of Pittsburgh School of
MedicineMedicine Pittsburgh, PA, 15213Pittsburgh, PA, 15213 412-624-4012412-624-4012 [email protected]@pitt.edu