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Exercise and Aging Skeletal Muscle

• 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

– 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 - 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, post-menopause, 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:

– 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: 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

• 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 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– Progress carefully with intensity and duration– Warm up slowly and carefully– Cool down slowly - to less than 100bpm– Stretching - reduce DOMS