Use it or lose it
If you want to keep well as you get older, adopt the " use it or lose it" philosophy.
It is depressing to think that each day we are not only getting older but also deteriorating in health and fitness. And not just individually. The nation as a whole is following the same pattern - over the past 20 years the number of people aged over 65 has more than doubled. Unless more attention is paid to health- related fitness, the strain on the medical services will soon become intolerable.
Why does it happen?
The decline in fitness as one gets older can be attributed simply to the ageing process, or just as equally to a reduction in physical activity. It is probably a combination of the two. Ageing per se will contribute to performance decrements, but the lifestyle of the older population does appear to lack the sort of regular, suitable physical activity sufficient to maintain health and fitness. As with all components of fitness, the 'use it or lose it' philosophy is particularly appropriate for the ageing population.
Physiologists have tried to establish the mechanisms behind this inevitable drop in performance by examining people of different ages. One index of aerobic ability, V02max, has been seen to fall with age. By the age of 65, values have usually decreased by a staggering 70 per cent from what they were at the age of 20. This rate of decline appears fairly consistent regardless of whether you are sedentary or trained.
Heart rate and stroke volume
The decline in V02max is a function of both central and peripheral factors in the cardiorespiratory system. Probably the most important is the decrease in maximum heart rate seen with increasing age. Look at any heart-rate training chart in a gym and you will see that you can establish an estimate of your maximum heart rate by subtracting your age from 220. This implies that your maximum heart rate drops by one beat per minute per year.
There is also a decrease in the function of the cardiac muscle itself, including the oxygen supply to that vital muscle, which means that your stroke volume, the amount of blood pumped in each beat, also drops with age. The net effect is that there is less blood being pumped around your body during high- intensity exercise, leaving a reduced oxygen supply to the muscles.
Flexibility, fat, and muscle strength
Aerobic capacity is not the only aspect of fitness that deteriorates with age. Flexibility will also decline from as early as the teenage years unless regular stretching exercises are carried out to prevent progressive stiffness. Body fat also increases with age - indeed, such is the inevitability of this increase that age is used within all equations to estimate body fat from skinfold thicknesses. The accumulation of fat need not just be in the .more obvious subcutaneous area but internally as well.
Muscle strength and power also decrease with age. This is due to a variety of factors, particularly atrophy, the wastage of muscle, caused by lack of use. This is another example of the 'use it or lose it' philosophy. Just as a muscle grows in response to strength training (hypertrophy), it will become smaller if it is not trained.
A vicious cycle - and how to reverse it
Although the impact on health of the ageing process may not be so crucial for the fitter subsections of society - those who are involved in some sort of physical activity - it is much more serious for the less fit majority. Some individuals will struggle to walk up a 1-in-7 slope after the age of 40 without heavy breathing and discomfort. Such discomfort will be enough to discourage them from future activity, which in turn leads to a greater decrease in muscle function and aerobic fitness, which makes future exercise even harder. A vicious cycle of decline develops.
The good news, however, is that no matter how old or unfit you are, you are still trainable. This has been clearly demonstrated by a number of research projects in the past few years.
Two projects from Ontario, Canada, have examined ageing populations. In the first (Canadian Journal of Applied Physiology, 19 (4), 366-378,1993), four males of just under 60 years of age were given a daily training programme for 12 weeks. The training was localised, isolating the muscles in the dominant wrist, to enable comparisons with the untrained, non-dominant wrist. After six weeks of the programme, power in the forearm had increased by 14 per cent, while endurance time for a task with the same muscles had improved by 34 per cent after six weeks and 58 per cent after the full 12 weeks. The greater increase in endurance as opposed to power was more a function of the training programme applied than a statement of the pattern of physical changes after training in the aged.
The other project (Journal of Applied Physiology, 73 (2), 452-457, 1992) examined eight females whose average age was 67. The subjects trained for about 30 minutes, four times a week for a total of nine weeks. The all-important intensity was a typical 70% V02max, which equates to about 80 per cent of maximum heart rate. Such a programme,.focusing this time on aerobic fitness, boosted V02max by 10.6 per cent and saw body mass drop by 2.1 per cent. More importantly, the time to fatigue in a submaximal test jumped by an astonishing 180 per cent! This great leap in endurance performance is surprising at first compared to the more moderate rise in V02max, but can be explained by the fact that endurance time to fatigue is a function of relative fitness, which will increase with a decreasing work rate.
Differences between men and women
A similar project from St Louis, Missouri (Journal of Applied Physiology, 75 (2), 849-855,1993) examined both males and females. The 15 males and 16 females? whose ages averaged 64 years, completed a training programme that lasted between nine and 12 months. The more substantial programme consisted of 45 minutes of exercise per day-for four days per week. The intensity ranged between 70-85 per cent of maximum heart rate and the work included walking uphill on a treadmill, running on an indoor track, cycling and rowing. Both males and females enjoyed a boost in
V02max of about 20 per cent. There was, however, a difference in the factors that caused such an increase: In the men, a significant increase in stroke volume was the main factor, whereas in the women an increase in the extraction of oxygen within the muscle was more important by far. The men, therefore, showed similar adaptations to young adults, in that the stroke volume is the main protagonist in boosting V02max.
Another project from the same centre gave a similar training programme to 23 healthy males and females, again of about 64 years of age. The duration of the programme was also nine to 12 months and the intensity at 80 per cent of maximum heart rate. A similar gain in V02max was seen, this time of 23 per cent, but in this study adaptations within the muscle were also scrutinised. The amount of aerobic enzymes within the muscle was significantly increased after training and the capillary supply was also greatly enhanced. Such a project shows that, given an adequate training stimulus, the changes seen in muscles of elderly subjects in response to a training programme are similar to those seen in younger individuals.
Atrophy can be reversed
Two other projects have looked at populations even older than those already mentioned. A study from Gothenberg (Journal of Applied Physiology, 73 (6), 2517-2523,1992) investigated the responses to a strength-training programme in 78-84-year-old men, who trained their quadriceps muscles two to three times a week It was seen that the training gave significant strength increases in the trained leg, as well as a 3 per cent increase in the cross-sectional area of the musculature. This not only shows that the atrophy can be halted in an ageing population but that given an adequate training stimulus, hypertrophy s still possible.
Looking at an older population still (Journal of the American Medical Association, 263, 3029-3034, 1990, 87-96-year-olds who performed weight-training exercises for eight weeks enjoyed strength gains of nearly double their pre-training values, along with a 10 per cent increase in muscle size. This means that strength gains are indeed possible regardless of age. Although these are partly a function of hypertrophy, an increase in skill and coordination is far more responsible for the increase in strength.
So the best news is undoubtedly that, whatever nick you are currently in, it is possible to improve your condition. If aerobic exercise is your choice, make sure the intensity is sufficient (80 per cent of maximum heart rate has been seen to be effective) and if bone health is a priority it is better to undertake exercise that involves impact such as walking or running as opposed to non-weight-bearing exercise like rowing cycling or swimming. This is because bone density responds to mild impact. Muscle strength and tone are important particularly for joint stability. If you maintain muscle strength and aerobic fitness by a little regular conditioning training, you can avoid the vicious cycle of decline and a dramatic drop in health.
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