Exercise and Aging Skeletal Muscle

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Exercise and Aging Skeletal Muscle

• Brooks - Ch 32
• Brooks - Ch 19 (p444-451)

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Outline

• Aging introduction
• Physiological capacity and aging
• CV and skeletal muscle only
• Aging process
• Exercise Prescription

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Aging

• Decline of physiological capacity is an
  inevitable consequence of aging
• physical inactivity may contribute to these
  declines
• complicating the quantification of the effects of
  aging
• Aging involves diminished capacity to regulate
  internal environment
• Body structures are less capable and less
  resilient
• Reduced capacity is evident in
• Reaction time, disease resistance, work capacity,
  and recovery time
• Body composition with aging
• inc body fat / dec lean body mass
• muscle size peaks at 25-30 yrs
• Resting Metabolic Rate (RMR)
• decline associated with decreased muscle mass

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Life expectancy, Life 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 changed
• 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

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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 of theses factors can be positively impacted
  by training

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Physiological Capacity

• Maximal O2 consumption and age
• VO2 max declines 30 (age 20-65)
• Fig 32-2 - (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

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Physiological Capacity

• Heart Rate and age
• Sub max - HR lower at relative intensity but the
  same at any given absolute intensity
• Cardiovascular drift is higher with age
• Longer recovery time back to resting values from
  submaximal and maximal exercise
• Increased cardiovascular drift
• Decreased b?- adrenergic responsiveness
• decreased max HR
• decreased contractility

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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
• ? 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
• Slower relaxation of ventricular wall
• SV changes rely more on Frank Starling due to
  reduced contractility

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Vascular System

• Poor peripheral vascular tone
• Varicose veins
• Reduces venous return affecting EDV and SV
• Vascular stiffness ? the peripheral resistance, ?
  the afterload of the heart.
• ? peripheral resistance also raises SBP during
  rest and exercise (no change in DBP).
• Capacity of autonomic reflexes that control blood
  flow is reduced
• At rest circulation to periphery is poor (cold)
• During exercise circ to periphery is too high
• Greater incidence of orthostatic intolerance
• Decreased plasma, red cell and total blood volume

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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
• ? capillary/fiber 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

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Skeletal Muscle

• Loss of muscle mass and strength can severely
  impact quality of life
• Muscle strength decreases approximately 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
• ? size and of muscle fibers and motor units
• ? in connective tissue and fat
• Severe loss of contractile elements - 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.
• Muscle is less excitable, greater refractory
  period
• ? maximum contractile velocity
• There is loss of biochemical capacity with age.
• ? of ATP and CP
• ? 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
• Some studies show higher AMPkinase activity at
  rest and after exercise - may have impact on type
  II fiber hypertrophy/atrophy
• Aged muscle may have better metabolic economy and
  be more fatigue resistant

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Gordon,SE et al Exerc Sport Sci Rev Vol 36 no 4
pp179-186, 2008
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Kent-Braun, JA Exerc Sport Sci Rev Vol 37 no 1
pp3-9, 2009
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The Aging Process

• 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, wear and tear, autoimmune
  reaction, problems with cell division,
• abnormalities of genetic function
• free radicals (ROS), radiation, toxins
• Correlation between age and accumulation of
  oxidative damage due to ROS - Free Radical Theory
  of Aging
• ROS act on lipids, protein and DNA
• Causal role for oxidative stress in aging process
  now well supported
• Eg Hydroxyl radical (OH?) causes DNA lesions
• Eg Superoxide anion thought to act on
  Mitochondrial DNA
• oxo8dG - guanine oxidation often studied as it
  pairs with Adenine instead of Cytosine and a
  potential mutation

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Portrait of typical 45 year old male and female,
1981 and 2007
Canadian Health Measures - Jan 2010, Statistics
Canada
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Aging, Lifestyle and Disease

• Lifestyle choices (deconditioning)
• Some people physically deteriorate with age due
  to a lack of exercise, obesity, poor diet,
  smoking, and stress.
• Others are active and 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
• Sedentary Physiology
• independent risk factor for CVD, some Cancers

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Prolonged uninterrupted sitting, independent of
physical activity may be a risk factor for
chronic disease.
Fig. 1. The movement continuum, illustrating the
different focus of sedentary physiology and
exercise physiology. METs, metabolic equivalent
tasks.
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Fig. 3. Illustration of accelerometer data
portraying an active couch potato (moderate to
vigorous intensity physical activity
meeting guidelines considered physically
active but also a high level of sedentary
behaviour) versus an active non-couch potato
(similar level of moderate to vigorous intensity
physical activity but low level of sedentary
behaviour). (From Dunstan et al. 2010a,
reproduced with permission of Touch Briefings,
European Endocrinology, Vol. 6, p. 21, 2010.)
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Fig. 4. Portrayal of significantly different
patterns of breaks in sedentary time, based on
accelerometer data from 2 different
individuals (a prolonger and a breaker).
(From Dunstan et al. 2010a, reproduced with
permission of Touch Briefings, European
Endocrinology, Vol. 6, p. 21, 2010.)
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Dietary Restriction and Aging

• Dietary restriction extends lifespan in rats and
  monkeys by 30-50
• reduces age related diseases
• Humans? - Okinawa diet 20 less calories, 300
  vegetable intake, low in fat and sugar - results?
• May retard basic metabolism and biological
  processes of aging
• May suppress age-related pathologies -
• found to impact immune system, protein turnover,
  bone loss, neural degeneration
• Reduces oxidative stress by ROS through increased
  antioxidant activity
• Observe significant decreases in oxo8dG DNA
  lesions in rodents

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Resistance Training Response

• Exercise training provides psychological benefits
• Improved cognitive function, self efficacy and
  reduced depression
• Training does not retard the aging process, it
  just allows the person to perform at a higher
  level - Fig 32.2
• Strength training
• Relative strength ? with training are similar in
  young and old individuals. - Only short term
  studies available
• 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

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Endurance Training

• Aerobic Endurance Training helps
• Maintain CV function and enhances exercise
  capacity
• Reduces risks for HD, diabetes, insulin
  resistance and some cancers
• May attenuate age related increase in ROS DNA
  lesions (oxo8dG)
• Similar improvements in Aerobic capacity for
  young and old
• 6 months 20 increase in VO2max
• Observe
• 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 to be
  independent
• 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
• however caution must be taken with the elderly to
  ? the risk of injury.
• Elderly have more abnormal ECGs during exercise.
• Start slowly with walking or swimming - low
  impact
• 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
• 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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TABLE 1. ACSM/AHA physical activity
recommendations for older adults. 150 min / wk
of physical activity for health benefits,
additional benefits occur with additional F, I,
and T - older adults should be as physically
active as their abilities and conditions
allow. Frequency moderate-intensity at least 30
or up to 60 (for greater benefit) min / day in
bouts of at least 10 min each to total 150300
min/wk, at least 2030 min / day or more of
vigorous-intensity activities to total 75150 min
/ wk, an equivalent combination of moderate and
vigorous activity. Intensity On a 0 to 10 scale,
5 to 6 for moderate and 7 to 8 for
vigorous Duration For moderate-intensity
activities, accumulate at least 30 min/day in
bouts of at least 10 min each or at least 20
min/day of continuous activity for
vigorous-intensity activities. Type Any modality
that does not impose excessive orthopedic stress
walking is the most common type of activity.
Aquatic exercise and stationary cycle exercise
may be advantageous for those with limited
tolerance for weight bearing activity.
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Resistance exercise for older adults Frequency
At least 2 days / wk Intensity Between moderate-
(56) and vigorous- (78) intensity on a scale of
0 to 10. Type Progressive weight training
program or weight bearing calisthenics (810
exercises involving the major muscle groups of
812 repetitions each), stair climbing, and
other strengthening activities that use the major
muscle groups. Flexibility exercise for older
adults Frequency At least 2 d/wk. Intensity
Moderate (56) intensity on a scale of 0 to
10. Type Any activities that maintain or
increase flexibility using sustained stretches
for each major muscle group and static rather
than ballistic movements.
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Balance exercise for frequent fallers or
individuals with mobility problems Because of a
lack of adequate research evidence, there are
currently no specific recommendations regarding
specific frequency, intensity, or type of balance
exercises for older adults. ACSM recommends
using activities that include the following 1)
progressively difficult postures that gradually
reduce the base of support (e.g.,two-legged
stand, semi-tandem stand, tandem stand,
one-legged stand), 2) dynamic movements that
perturb the center of gravity (e.g., tandem walk,
circle turns), 3) stressing postural muscle
groups (e.g., heel stands, toe stands), or 4)
reducing sensory input (e.g., standing with eyes
closed).
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The ACSM/AHA Guidelines recommend the following
special considerations for older adults. - The
intensity and duration of physical activity
should be low at the outset for older adults who
are highly deconditioned, functionally limited,
or have chronic conditions that affect their
ability to perform physical tasks. - The
progression of activities should be individual
and tailored to tolerance and preference a
conservative approach may be necessary for the
most deconditioned and physically limited older
adults. - Muscle strengthening activities
and/or balance training may need to precede
aerobic training activities among very frail
individuals. - Older adults should exceed the
recommended minimums if they desire to improve
their fitness. - If chronic conditions preclude
activity at the recommended minimum amount, older
adults should perform physical activities as
tolerated so as to avoid being sedentary.