Muscle fibre illustration of man running exercise by Matthew Harvey

Aging & Activity

Posted on Posted in Exercise

A look at how activity affects aging… by Nicole Fish

I saw a fabulous picture the other day with an older lady playing soccer with a bunch of kids that said, “Just because you are getting old, doesn’t mean you have to be old”. We often think of aging, especially after 60, as a lifetime ahead of doom and gloom, filled with aches, pains and loss of function. This however needn’t be the case for most individuals. As Brian Sharkey put it; maintaining an active lifestyle will add life to your years as well as years to your life!(Sharkey, 1997).

We all know that as we mature through life, there are many physiological changes that occur within the body. These include changes in: bone mass; muscles (generally with associated loss of strength); cardiovascular fitness; respiratory fitness; the nervous system; metabolism and body composition. Research has not been conclusive as to whether this is due to age per se or as a result of decreased activity that generally occurs with aging. However, research has proven that maintaining an active lifestyle has slowed the deterioration process.

Let’s have a brief look at how exercise can slow the process of deterioration.

Changes in muscle – After the age of 60, there is a decrease in the number, rather than the size, of muscle fibres, resulting in a loss of strength. However, this loss of strength can be counteracted by regular strength training which results in an increase in muscle fibre size, to compensate for the decrease in number of muscle fibres.
Changes in bone density – generally from the age of 30 there is a gradual decrease in bone mass. However, regular exercise can help to improve bone density, and slow the decline, by stimulating osteoblast formation due to the increased stress placed on the bones. This is why weight bearing activities, like walking and jogging, are essential to maintaining good bone density, as these are influenced both by the force of gravity on the bone as well as the forces associated with muscle contraction.
Changes in Cardiorespiratory Fitness – Aging affects both cardiac function as well as peripheral circulation. The maximum cardiac output (the volume of blood being pumped by the heart in one minute) is reduced as much as 50% from the teen years to the age of 80. This means that the maximum achievable muscle power is greatly reduced (due to less oxygen and nutrients being delivered to the muscles). Due to the decrease in bone mass as you age, the ribcage may be affected, which may mean your ribcage is less able to expand and contract during breathing. The diaphragm may also become weakened which may prevent you from inhaling and exhaling fully, resulting in tiredness and shortness of breath. All these things mentioned, results in a decrease in VO2max. However, research has shown that older adults can achieve the same percentage increase in VO2max in response to endurance exercise training, as their younger counterparts.
Changes in the Nervous System – As one ages, your brain and spinal cord lose nerve cells, which results in a decrease in conduction velocities and slowed reaction times. This makes individuals less able to react timeously to a situation (e.g. tripping over a step) and increases the likelihood of a fall. There is strong evidence to suggest that regular exercise delays the symptoms of aging in the nervous system. Regular balance exercises have also been proven to reduce the risk of falling by improving one’s ability to maintain and control their body position.
Changes in Metabolism and body composition – With age the basal metabolic rate (the rate at which the body uses energy whilst at rest) decreases. As does glucose tolerance diminish and relative body fat increase as lean body mass decreases. With regular exercise there is a decrease in insulin resistance and improved blood sugar control. Regular exercise helps to reduce body fat and mass putting less pressure on the joints.

With all of the favourable physiological adaptations that come with regular exercise, suddenly getting old doesn’t seem all doom and gloom. So how much exercise should we be getting? Ideally, according to the ACSM guidelines for healthy individuals, one should aim to exercise for 20-60 minutes at 55/65% – 90% of your maximum heart rate, three to five times per week. Aiming to do a variety of exercises (like walking, swimming, aquarobics, weight training) will be more beneficial in the long term as there is less chance of boredom setting in, and finding classes to join will add psychological benefits to each session as you get to socialise with others.

This was another slogan I saw on a t-shirt recently which I really loved:
“Growing old is mandatory, growing up is optional”

References:

1. Brukner P and Kahn K. Clinical Sports Medicine, McGraw-Hill Book Companies Inc, 2001
2. De Vries and Housh, Physiology of Exercise, 5th edition, McGraw-Hill Book Companies Inc,1994
3. Guyton AC, M.D, Textbook of medical physiology, 8th edition, WB Saunders Company, 1991
4. Powers and Howley, Exercise Physiology, 4th edition, McGraw-Hills Companies Inc, 2001
5. Sharkey B, PhD, Fitness and Health, 4th edition, Human Kinetics, 1990
6. http://www.acsm.org/docs/current-comments/exerciseandtheolderadult.pdf
7. http://www.nlm.nih.gov/medlineplus/ency/article/004011.htm
8. http://www.nlm.nih.gov/medlineplus/ency/article/004023.htm
9. http://nihseniorhealth.gov/exerciseandphysicalactivityexercisestotry/balanceexercises/01.html

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