Transcript Exercise and Aging Skeletal Muscle

Exercise and Aging
Skeletal Muscle
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Brooks - Ch 32
Brooks - Ch 19 (p p414-418)
Outline
Aging introduction
Aging process
Physiological capacity and aging
– CV, pulmonary, skeletal, joints, sk
muscle, disease risk, body composition
• Exercise Prescription
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Aging
• Decline of physiological capacity is
inevitable consequence of aging
– physical inactivity may contribute to
these declines
– complicating the quantification of the
effects of aging
• Body composition with aging
• inc % body fat / dec lean body mass
– studies illustrate selective decline in sk
ms protein vs non muscle protein
– body K+ and Nitrogen levels
• muscle peaks at 25-30 yrs
– decline in X sec area, ms density
– inc intra-muscular fat
• Resting Metabolic Rate (RMR)
– decline associated with dec ms mass
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Life expectancy, Span, and
Morbidity
• Lifestyle (diet, exercise) will influence
performance and health with aging,
but will not halt the aging process.
• Life expectancy has changed
dramatically in this century
– 1900: 47 years ; 2000: 76 years
– Maximum lifespan (100 years) has not
• Quality of life, wellness, is important
– North Americans only have healthy
quality life during 85% of their
lifespan, on average
– Good lifestyle choices can compress
morbidity - state in which they can no
care for themselves
– Reducing morbidity from 5-10 years to
1 or 2 can add quality years to your life
– Table 32-1
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Aging and Exercise
• Lifestyle choices (deconditioning)
– Some people physically deteriorate with
age due to a lack of exercise, obesity,
poor diet, smoking, and stress.
– Other individuals are active and are still
fit in their 50s, 60s and 70s.
• Disease and physiological function
– Disease further complicates our
understanding of the aging process.
 osteoarthritis, atherosclerosis
– Sedentary death syndrome (SeDS)
• Clear that adaptation to exercise has a
genetic basis (plasticity)
• Effort to find molecular proof that physical
inactivity is an actual cause of chronic
disease
• Some researches want to move away from
using sedentary individuals as controls in
experiments - eg GLUT 4 and diabetes
– Physiological systems vary in the extent
to which they deteriorate with age.
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The Aging Process
• Aging involves diminished capacity to
regulate internal environment
• Body structures are less capable and less
resilient
• Reduced capacity is evident in;
– Reaction time, resistance to disease, work
capacity, and recovery time
• Table 32-2 (good summary)
– Reduced capacity of many systems
• Genetics has an important influence on
length of life; genetics in concert with
environmental factors affects the quality of
that life
• Aging may be related to;
– accumulated injury, autoimmune reaction,
problems with cell division,
– abnormalities of genetic function (free radicals,
radiation, toxins),
– wear and tear
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Dietary Restriction and Aging
• Dietary restriction extended mean
lifespan in rats by 30-50 %
– Similar results in monkeys
• Several possible explanations :
• Retardation of basic metabolism and
biological processes of aging
• Suppression of age-related
pathologies – found to impact immune system,
protein turnover, bone loss, neural
degeneration
• Reduction of oxidative stress by
ROS through increased antioxidant
activity
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Physiological Capacity
• Physiological functioning peaks ~ age 30
• Table 32-3
• ~.75 to 1 % decline per year after 30
– Declines in VO2 max, Q max, strength ,power,
and neural function; also increases in body fat
• All positively impacted by training
• Maximal O2 consumption and age
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VO2 max declines ~30% (age 20-65)
Fig 32-1 - (training and age vs VO2 max)
Significant individual variability
Similar declines with age in trained and
untrained - trained has higher capacity
– Due to decrease in max HR, SV, Power, fat free
mass and A-V O2 difference
• Heart Rate and age
– Sub max - HR lower at relative intensity but
higher at same absolute intensity
– Cardiovascular drift is higher with age
– Longer recovery time
– Dec b- adrenergic responsiveness (dec HR max)
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Stroke Volume and Cardiac
Output (Q)
• Aging  the hearts capacity to pump blood
• Q and SV are less during exercise
– Both relative and absolute intensity
• Gradual loss of contractile strength due to
– dec Ca ATPase and myosin ATPase activities
and myocardial ischemia
• Often, heart wall stiffens, delaying
ventricular filling - dec SV… dec Q
• The elasticity of blood vessels and the
heart  due to connective tissue changes.
• Heart mass usually  and there are fibrotic
changes in the heart valves
• Vascular stiffness  the peripheral
resistance,  the afterload of the heart.
–  peripheral resistance also raises SBP during
rest and exercise (no change in DBP).
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A-V O2 difference
• Dec with age - contributing to dec
aerobic capacity
• Decreases from 16 vol % (20 yrs) to
12 vol % (65 yrs) ( mlO2/dl)
• Reductions due to
–  fiber/capillary ratio
–  total hemoglobin
–  respiratory capacity of muscle
–  in muscle mito mass
–  oxidative enzymes
• However, A-VO2 is higher at any
absolute exercise intensity with age
• Capacity of autonomic reflexes that
control blood flow is reduced
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Pulmonary Function
• The lungs have a large reserve capacity to
meet ventilation requirements of exercise
• Reserve begins to deteriorate between 30,
more rapidly after 60
• Changes include;
– Inc size of alveoli (dec vasculature)
– Dec elasticity of support structure
• increases work of breathing
– Weakening of respiratory muscle
• Deterioration is similar to that in CV
system, and does not limit endurance
performance in young or old (disease free)
• Training will improve max vent capacity in
parallel with changes in Q
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Skeletal System
• Bone loss is a serious problem in older
people, particularly women.
– Women begin to lose bone mineral at 30 and
men at 50 years of age.
• Estrogen deficiency in women, postmenopause, is thought to accelerate bone
loss
– HRT - (hormone replacement therapy) is no longer
recommended over long time- due to CVD and
Breast cancer risks
• Although the exact mechanism of bone
loss is not completely understood,
contributing factors are;
– inactivity, diet, skeletal blood flow and
endocrine function.
• Exercise is important in prevention and
treatment of osteoporosis
– Bones become stronger when stresses are
placed on them
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Joints
• Joints become less stable and less
mobile with age.
• Aging is associated with:
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degradation of collagen fibers;
cross-link formation;
fibrous synovial membranes;
joint surface deterioration;
 viscosity of synovial fluid.
• It is difficult to separate aging from
accumulated wear and tear
– Trauma to the joint cartilage results in
formation of scar tissue
– impairs ROM
• ROM exercises can  flexibility.
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Skeletal Muscle
• Loss of muscle mass and strength
can severely impact quality of life
• Muscle strength decreases aprox 8%
per decade after the age of 45.
• Aging results in a  in isometric and
dynamic strength and speed of
movement.
• Strength losses are due to:
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 size and # of muscle fibers
atrophy or loss of type II fibers
 in the respiratory capacity of muscle
 in connective tissue and fat
• Eg sarcopenia
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Muscle Fiber Types
• With age there is a selective loss of type II
fibers,
–  is more rapid in the lower body.
–  available strength and power.
• The mechanisms involved in muscle
contraction are also impaired:
– less excitable, greater refractory period
– [ ] of ATP and CP are
– maximum contractile velocity 
• There is loss of biochemical capacity
with age.
–  in glycolytic enzymes (LDH).
– There are no changes or slight  in oxidative
enzymes
• *Controversy over whether there is a decrease
in oxidative capacity or not with ageing
• Relative strength  with training are
similar in young and old individuals.
– Only short term studies available
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CVD risk factors
• Exercise (even low intensity) has
health benefits in the elderly.
• Exercise  blood insulin levels and
improves glucose tolerance (if impaired)
and insulin sensitivity
– Less dramatic impact than in young
• Exercise  resting and exercise SBP.
• Exercise improves plasma lipid
profiles: plasma triglyceride and
cholesterol;  HDL
• Metabolic syndrome
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Body composition and Stature
• Body composition and stature
change markedly with age.
• Body weight  from age 20 to 60
and then .
– due to an  in % body fat.
• A greater proportion of body fat is
stored internally rather than
subcutaneously.
• Stature  with age (avg 6 cm ) due
to:
– rounding of the back(kyphosis); disc
compression; vertebrae deterioration.
• Exercise is very important in
managing body composition in the
elderly.
– Maintain lean body mass to maintain
metabolic rate and minimize fat gain
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Training Response
• Older people readily respond to endurance
and strength training
• Endurance Training helps
– Maintain CV function
– Enhances exercise capacity
– Reduces risks for heart disease, diabetes, insulin
resistance and some cancers
• Strength training
– Helps prevent loss of muscle mass and strength
– Prevents bone mineral loss
– Improves postural stability reduces risks of falls
and fractures
– Mobility exercises improve flexibility and joint
health
• Training also provides psychological
benefits
– Improved cognitive function, reduced
depression and enhanced self efficacy
• Training does not retard the aging process,
it just allows the person to perform at a
higher level - Fig 32.1
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Endurance Training
• Similar improvements in Aerobic
capacity for young and old
– 6 months ~20% increase in VO2max
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Dec submax HR at absolute load
Dec resting and submax SBP
Faster recovery of HR
Improvements in ECG abnormalities
Inc SV and Q
• Elderly require a VO2max of ~20
ml/Kg for an independent lifestyle
– A conservative well structured program
can bring most elderly to this level of
fitness within ~3 months
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Exercise Prescription
• The principles of exercise prescription
are the same for everyone,
– however caution must be taken with the
elderly to  the risk of injury.
• Elderly have more abnormal ECG’s
during exercise.
– Start slowly with walking and
swimming - low impact exercises
– Running, racket-ball… only when fit
• Problems with using estimates of
Max HR for prescribing intensity
– considerably variation in the elderly
• (Max HR range : 105 - 200 for 60yr olds)
• Principles
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Progress carefully with intensity and duration
Warm up slowly and carefully
Cool down slowly - to less than 100bpm
Stretching - reduce DOMS
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