The effect of exercise on aging.

We all have a chronological age, even though there are some old people who do not know the year they were born, but the rest of us have birthdays which define our chronological age. However, we also have a biological age which can be older or younger than our chronological age. This accounts for why some people look older than their age, while others look younger. Thus, while aging is inevitable, the rate of aging can vary. Our rate of aging depends on how our cells age.

Human beings are complex multicellular organisms with our basic building block being the cell. Billions of years ago single celled organisms got together into colonies to become more efficient and then developed into multicellular organisms in the form of simple plants and animals. You can still find some very ancient forms of life, like sponges or algae on our seashores. The basic unit of life is cells which are programmed through our DNA, our genetic blueprint contained in the chromosomes inherited from our parents. The chromosomes are contained in the nucleus of the cell, but cells also have other organelles to enable them to perform functions such as respiration, making proteins and expelling waste products. The Intracellular body which generates energy is the mitochondrion; there are also structures which mop up the waste products and either hold them in a dustbin within the cell, or extrude them into the extracellular environment.

As we age some of these cellular functions become less efficient. For example, the chromosomes are folded into the famous double helix and have caps at the ends of the strands called telomeres which keep them from having loose ends (like the caps on the end of a shoelace), but as we get older the telomeres get shorter, and the DNA becomes more disorganised. This leads to mistakes in the instructions that the DNA sends out which can cause mutations which lead to cancer. The waste bins also get full, causing them to overflow and poison the intracellular environment, and the cells which patrol the body and detect foreign protein can drift off to sleep as we get older. These senescent cells then cause inflammation that leads to adverse effects in the blood vessels.

Our bodies are like a car which gets older but continues to run; the shock absorbers are gone, the electric windows don’t open, the seats sag, and the starter motor has failed, but it still goes from A to B. I used to own a car like this: it was beautiful when it first arrived, but after twenty years the shock absorbers and other such comforts were a thing of the past, but somehow it still ran. In aging our cells wear out, and our defence system doesn’t work very well, allowing increased inflammation and toxicity in our bodies. Like an old car we can keep going until we slowly disintegrate (die of old age), or we may stop suddenly due to a major problem (such as a heart attack). When Queen Elizabeth died, they put the cause of death on the death certificate as ‘old age’ because at age 96 she had just worn out.

Aging may be inevitable but recent research has demonstrated that exercise slows down the biological process at the level of our cells. Lab rats which were exercised had completely different more healthy cells and longer life expectancy compared to those that were not on an exercise program. Our cells are designed to respond positively to stress, not psychological stress, but stress such as exercise that makes the cells to work more efficiently. From an evolutionary point of view, we are built to respond to danger signals by producing certain hormones which keep us on our toes. When we have no stress, i.e. we have enough to eat and lead sedentary lives, our cells become lazy and less efficient. Doing exercises introduces the right kind of stress, as does a small amount of food deprivation (fasting or going for longer periods between meals), and these small stressors make our cells more efficient which slows the process of biological aging. On this basis scientists recommend that we exercise at least thirty minutes per day.