Physical activity and physical fitness have been linked with health and longevity since ancient times. The earliest records of organized exercise used for health promotion are found in China around 2500 BC. However, it was the Greek physicians of the fifth and early fourth centuries BC who established a tradition of maintaining positive health through 'regimen'- the combination of correct eating and exercise. Hippocrates (c.460-370 BC), often called the Father of Modern Medicine, wrote.
...all parts of the body which have a function, if used in moderation and exercised in labours in which each is accustomed, become thereby healthy, well-developed and age more slowly, but if unused and left idle they become liable to disease, defective in growth and age quickly.
Modern day exercise research began after the Second World War in the context of post-war aspirations to build a better world. Public health was changing to focus on chronic, non-communicable diseases and the modification of individual behavior. Whilst Doll and Hill worked on the links between smoking and lung cancer, Professor Jeremy Morris and his colleagues set out to test the hypothesis that deaths from coronary heart disease (CHD) were less common among men engaged in physically active work than among those in sedentary jobs. In seminal papers published in 1953, they reported that conductors working on London's double-decker buses who climbed around 600 stairs per working day experienced less than half the incidence of heart attacks as the sedentary drivers who sat for 90% of their shift.
Subsequent studies by Morris and others, in particular Morris's close friend Ralph Paffenbarger in the US, have confirmed that the postponement of cardiovascular disease through exercise represents a cause and effect relationship. For their contribution, Morris and Paffenbarger were in 1996 jointly awarded the first International Olympic Medal and Prize for research in exercise sciences. In the 50 years since Morris's early papers, research into the influence of physical activity on health has burgeoned.
The Effects of Inactivity
Prolonged inactivity has many detrimental effects on the muscles, bones, and cardiovascular system of the human body. Disuse adversely affects all body tissues and all body functions. For example, bed rest leads to a muscle protein loss of 8 grams per day, a bone calcium loss of 1.54 grams per week, a decrease in fitness by 0.8% per day, and a 10-15% decrease in plasma volume within several days.
Few humans undergo prolonged bed rest. However, nearly all people have exercised for a certain period of time and then for various reasons reduced or terminated formal exercise while continuing normal day-to-day activities. This period of detraining leads to many changes in physiological function.
Just as the body adapts negatively without exercise, it can adapt positively again with exercise. Researchers have shown that the rise in aerobic power with training is just as rapid as its fall without it. Even well trained athletes undergo a period of detraining if they stop exercising. The positive news is that even people who have never exercised much before in their life previously, have a chance at any age to turn it all around and gain positive adaptations to exercise. Research shows that even people 85 years and older benefit from the positive adaptations to exercise, regardless of their history of exercise.