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Nowadays, the general public has become more aware of the importance of participating in physical activity throughout life. During the last decade, researches on the relationship between physical activity and health issues in aged people have increased markedly. Findings suggest that the typical aging process can, in fact be slowed, through regular exercise. In addition, scientific evidences link regular exercise with diseases prevention and treatment. The remarkable benefits that can be gained through physical activity boosted a large number of old people around the world to participate in sports and physical activities, at different level and on a regular basic. It is now recognised that participation in sports or in any kind of physical activity on a regular basic plays an important role in ensuring that aging does not become synonymous with decline, deprivation, and despair.
The shape of the modern society might be a key factor for the decline in physical activity when people getting older. Technology has made virtually every aspect of life less physically demanding. Consequently, older people who choose to participate in competitive sports or exhaustive physical activities do not follow natural human behavior patterns. Older people, who participate in competitive sports or exhaustive physical activities, have achieved some exceptional records in sport events, like in running and swimming. However, Trappe et al (1996) suggested that running performance in general, declines with age, and the rate of this decline appears to be independent of distance. In this point it will be interesting to highlight the decline of the world record times for both 100m and 10km runs by about 1% per year from age 25 to age 60 (appendix I; figure 1, 2). In addition, U.S masters national record in the 100m freestyle decreased by about 1% per year for both men and women from age 25 to age 75 (appendix I; figure 3). Tanaka and Seals (1997) showed that swimming performance in 1,500m declined steadily from age 35 to 70 years. Moreover, strength declines when people getting older. Mens US National Masters records for the sum of four power lifts decline at a steady rate of about 12.1kg, approximately 1.8% per year (appendix I; figure 4). National and world records figures suggest that sport performance decline at a steady rate during middle and advanced ages. These declines in performance result from decrements in both muscular and cardiovascular endurance and strength. A further consideration of the underlying causes of these changes must be done in order to identify the relationship between aging, physiological changes, and physical activities.
The decline in cardiovascular capacity associated with aging has been well documented in prior studies (Astrand et al 1997; Kasch et al 1999), however, the mechanisms responsible for the decline in aerobic power remain poorly understood; and the degree to which the age-related changes are reversible remains unclear (Stratton et al 1994; McGuire et al 2001). Jackson et al (1995) stated three reasons for the diminution of VO2 max with increasing aging: a) sedentary life, b) body composition, and c) lifestyle. Furthermore, a latest position statement from the American college of sport medicine indicated a broad range of decline (5 to 15%) in VO2 max per decade (American college of sport medicine, 1998). The relationship between age, gender, and habitual physical activity appear to account for a considerable amount of the variance in rate on decline among healthy people. This decline in aerobic power is associated with functional changes such as heart rate, stroke volume, and cardiac output (appendix II).
According to previous researches, maximal heart rate (HRmax) declines with age, regardless of training status (Ogawa et al, 1992; Proctor and Joyner, 1997). The most popular equation for prediction of HRmax (220-idividuals age in years) reveals that HRmax declines when people get older. The decrease in HRmax is due largely to decreases in sympathetic nervous system activity and alterations in cardiac conduction system. Hoeldtke & Cilmi (1985) suggested that the rate at which catecholamines enters the circulation is increased in the elderly, but catecholamines production is normal. However, despite the normal production of catecholamines in aged people; White et al (1994) showed that myocardial tissue sensitivity to catecholamines decreases with increasing age across a large number of animal species. In addition, a number of studies suggested that the key signaling proteins (-adrenergic receptor, G protein, and adenyl citrate) involved in amplification and integration of extracellular signals in myocyte (from the sarcoplasmic reticulum to the intracellular effectors) reduced by 30 to 40% in older sedentary hearts (Rodeheffer et al, 1984; White et al, 1994). Therefore, it can be sustained that reduction in myocardial tissue, which is sensitivity to catecholamines, and reduction of the signaling proteins involved in amplification and integration of extracellular signals in myocyte are responsible for the HRmax decline in aged people.
The majority of studies also support that maximal cardiac output is also slightly reduced with age (Ogawa et al, 1992; Bogaard et al, 1997). In addition, the submaximal cardiac output response to exercise has been reported to be unchanged with age (Proctor et al 1998). However, McElvaney et al (1989) supported that the cardiac output of 65-year-old subjects was somewhat lower than in younger individual at any given absolute level of power output. Schulman et al (1992) suggested that the early diastolic left ventricular filling rate progressively slows after the age of 20; so that by age of 80, the rate is reduced by up to 50%. This reduction is attributed to structural (fibrous) changes in the left ventricular myocardium or to residual myofilament Ca++ activation from the preceding systole, resulting in prolonged isovolumic relaxation. Although left ventricular filling in early diastole is less in older than in younger people, filling in later diastole is greater, because the atrial contraction is augmented. Thus, end-diastolic volume increases slightly with age in men as long as the atrial contraction is normal. Fleg et al (1995) supported that ejection fraction, heart rate, and cardiac index were all reduced with age; however the end- diastolic volume index increased by 35% with age in men. Consequently, in older men, the early diastolic left ventricular filling volume increases during exercise. As a result, the end-diastolic volume, even at peak exercise, is not compromised because of a "stiff heart," and stroke volume during exercise is maintained in older persons. As a sequence, it can be supported that the reduction in maximum cardiac index that occurs in aged men is completely due to the age-associated reduction in maximum heart rate.
Furthermore, age-related losses of muscle strength result primary from the substantial loss of muscle mass that accompanies aging or decreased physical performance. Previous studies have shown that a decrease in both the number and size of muscle fibers (sarcopenia) occurs with aging (Aoyagi and Shephard, 1992; Trappe et al, 2001). Lexell et al (1988) suggested that 10% of the total number of fibers is lost per decade after the age of 50. Earlier studies have shown that the relative proportion of fast-twist (FT) muscle fibers decrease with age (Larsson et al, 1978), while the portion of slow twist (ST) fibers increases (Larsson, 1983). Although, the precise cause of this loss of FT fibers is unclear, Kamen et al (1995) suggested the number of FT motor neurons decreases during aging, which eliminates innervations of these muscle fibers. A further research in this area is needed in order to evaluate this finding.
A number of studies revealed that endurance exercise increase cardiovascular capacity in aging adults (Ogawa et al, 1992; Stratton et al, 1994; Bogaard et al, 1997). Hagberg et al (1989) examined the effects of endurance exercise training on maximal O2 consumption (VO2 max) and the cardiovascular responses to exercise of 70- to 79-yr-old healthy untrained men. According to their findings, the endurance training group increased its VO2 max by 16% during the first 13 wk of training and by a total of 22% after 26 wk of training; this group also increased its maximal O2 pulse, systolic blood pressure, and ventilation, and decreased its heart rate and perceived exertion during submaximal exercise. Thus healthy men in their 70s can respond to prolonged endurance exercise training with adaptations similar to those of younger individuals (Kohrt et al, 1991). In a recent study Darren et al (2001) found that age-related decline in aerobic power among 5 middle-aged men occurring over 30 years was completely reversed by a 6-month endurance training program. However, no subject achieved the same VO2 max attained after intensive training as young men. The improved aerobic power after training primarily was the result of peripheral adaptation, with no effective improvement in maximal oxygen delivery.
Additionally, several studies have shown that resistance exercise training can induce muscle hypertrophy and increase muscle protein synthesis, strength, mass, and quality, thus improving physical function in order adults (Frontera et al, 1988; Dupler and Cortes, 1993). Moritani and De Vries (1980) reported that 8 weeks of progressive resistance exercise training increased muscle strength similarly in young and elderly men; nevertheless, muscle hypertrophy did not occur in elderly men. In addition, Fiatarone (1994) showed that lower body resistance exercise training in 72- to 98-years-old physically frail nursing home residence increased muscle strength (113%) and gait velocity (12%), where the same variables remained unchanged in a nonexercising control group. Stair climbing power was increased by 28% for those who follow the resistance training program. Moreover, Kirkendall and Garrett (1998) showed that endurance training in older adults can improve the aerobic capacity of muscles, and resistance training can improve central nervous system recruitment of muscle, and increase muscle mass. Muscle strength also provides an alternative method of applying mechanical force to the bones, thus stimulating mineral deposition. Menkes et al (1993) found that increased muscle strength by 45%, also increased femoral density by 3.8% and lumbar density by 2% in 59-yr-old men. Therefore, old adults through resistance exercise can improve not only their muscle mass but also increase bones density.
When dealing with old adults, physical activity is also associated with diseases prevention and treatment. According to British heart association, diseases of the heart and circulatory system (cardiovascular disease or CVD) are the main cause of death in the UK: accounting for over 250,000 deaths in 1998. Physical activity can prevent old adults from developing hypertension. Studies have shown that dynamic exercise (Pescatello et al, 1991) or moderate-intensity exercise training (Hagberg et al, 1989) may decrease blood pressure (BP) in hypertensive men 60-69 years old. In addition, recent epidemiological studies indicated that individuals who maintaining a physically active lifestyle are much less likely to develop impaired glucose tolerance and non-insulin-dependent diabetes mellitus (Ivy, 1997; Wallberg-Henriksson et al, 1998). Moreover, through daily physical activities, people can reduce the risk to become obese, and likewise obese people to reduce their weight (Miller, 2001). Based on previous studies, any kind of physical activity can reduce the risk of cardiovascular diseases when you getting older (Morris et al; 1973; Paffenbarger et al, 1978; Morris et al, 1980; Blair et al, 1989; Lee et al, 2000; Dvorak et al, 2001). The general conclusion of the above studies was that: a) sedentary life associated with high incidence of coronary heart diseases, and b) approximately a doubling of risk of cardiovascular heart diseases when least active group compared to most active group.
Physical activity must be part of peoples daily life. Together with the nutritional and non-smoking habits; physical activity completes the healthy lifestyle puzzle. Through a simple training program (appendix III) aged adults can reduce the physiological aging processes. They can increase their fitness status, and as a result, to perform their daily activities much easier. In addition, physical activity can also reduce the risk for some serious diseases, like; cardiovascular diseases, obesity, diabetes and osteoporosis. Furthermore, physical activity can be used as a method of treatment for already diseased individuals. The most important of all is that people should start exercising from their early years of their life, since physical activity and generally participation in sport activities must be an integral component of their lifestyle.
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