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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 1 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 2 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 3 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. 4 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 5 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 6 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 b- adrenergic responsiveness (dec HR max) 7 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). 8 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 9 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 10 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 11 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. 12 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 13 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 14 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 15 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 16 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 17 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 18 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 19