The Effects of Aging

Humans are often assumed to be at their peak of physical fitness in their late 20’s, and in physical decline from the early 30’s onwards. Although the number of “older” athletes reaching the top of their sports well beyond this age shows that this need not necessarily be so, like it or not it is well documented that as time goes by it takes its toll on the human body. When you reach your sixties, fitness becomes an increasingly important factor in your general health and well-being. Your reaction times are 20 per cent slower than at their peak. In your seventies, you will use up to 50 per cent of your aerobic capacity just to do everyday tasks, such as getting the shopping in.

So how does Father Time exert these changes on us? Thinking mainly in terms of attributes that affect healthy individuals (rather than the increase of diseases that may affect us as we age) it is reported that our maximum heart rate and VO2 max decline, strength reduces, body fat increases, ability to clear lactic acid reduces and bone density declines.

The good news however, is that exercise can have a big impact in reducing and delaying these effects. For example one indisputable outcome of aging is declining aerobic horsepower. Classically, this is measured via VO2 max, your maximum rate of oxygen usage per unit of body weight. For sedentary people, VO2 max typically declines by about 10 percent per decade after age 30. For athletes who keep in training, the rate of decline can often be held to about half that.

With regards to cardiac capacity, although your maximum heart rate drops about one beat per minute each year, the stroke volume (the amount of blood pumped out by the left ventricle to the body) naturally increases with age to compensate for this. In theory this maintains the cardiac output (which is a function of stroke volume multiplied by heart rate) so the amount of oxygen reaching the muscles is the same. A 50-year-old's heart might not beat as rapidly as it once did, but it can pump at least as much blood per minute. However, stroke volume can be significantly improved (increased) through aerobic training, and therefore if your heart becomes more efficient (because it is pumping more blood through with each contraction) then it stands to reason that your heart rate, both measured whilst exercising and whilst at rest drops. This in turn means that you maintain a large differential between your maximum heart rate (which is lowering naturally with age) and your resting heart rate. In other words you still have a good range of heart rates to utilize for different training zones.

However, if the heart is delivering as much oxygen as before, but VO2 max is declining, it must be that the muscles are becoming less adept at using it. What precisely is going on is still being disputed. However, all parties seem to be in agreement that if you do not use your muscles then you lose certain types of muscles fibres. Strength training should not be seen as the preserve of young people, in fact it may be more important to include elements of this type of training as you age.

It comes down to “use it or loose it”. 'Evidence suggests that if you stay active, the rate of physical decline is halved,' claims Mike Stroud (Author of Survival of the Fittest). It's a comforting thought! A bit of an endurance junkie (i.e. with Sir Ranulph Fiennes he did the 7 marathons on 7 Continents in 7 days) he believes the body is tuned for slow-burn efforts during its whole lifespan and that we have an evolutionary capability for it. “People who are doing extreme endurance events are voluntarily accessing this survival capacity. You just have to ask your body hard enough.”

'Evidence suggests that if you stay active, the rate of physical decline is halved,' claims Stroud. Now that's a  comforting thought! MF