Transcript Exercise and Aging Skeletal Muscle

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
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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
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contractility
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
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–
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 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
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more fatigue resistant
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
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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 Adenine22
instead of Cytosine and a potential mutation
Portrait of typical 45 year old male and female, 1981 and 2007
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Canadian Health Measures - Jan 2010, Statistics Canada
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.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Fig. 1. The movement continuum, illustrating the different
focus of sedentary physiology and exercise physiology. METs,
metabolic equivalent tasks.
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QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
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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QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
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
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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 to be independent
– A conservative well structured program can bring most elderly to this
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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 ECG’s 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
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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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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 150–300 min/wk,
at least 20–30 min / day or more of vigorous-intensity activities to total 75–
150 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- (5–6) and vigorous- (7–8) intensity
on a scale of 0 to 10.
Type: Progressive weight training program or weight bearing
calisthenics (8–10 exercises involving the major muscle groups
of 8–12 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 (5–6) 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) 38
reducing sensory input (e.g., standing with eyes closed).
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
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as tolerated so as to avoid being sedentary
.