Lack of exercise is causing a deterioration in health, particularly among the middle-aged in developed countries. Many complaints about ill-health, pains, and the malfunctioning of various organs may be related to a subnormally functioning muscular system. Weak muscles often cause more passive structures of the body (joints, ligaments, and connective tissue) to be overloaded. Increasing mortality rates are associated with a higher incidence of cardiovascular disease and with a lower level of physical fitness.
Children have become more sedentary. They expend 500 calories less per day than they did 10 years ago; only one tenth as many children walk or cycle to school as did then. In a study to measure children's energy output, researchers found that virtually no children engaged in actitivities that would bring their heartbeat up to 140 per minute for 30 minutes a day.
The number of cars and the number of televisions owned by European households doubled in the 20 years up to 1997, which ties directly to a drop in exercise.