Immobility has a generally negative effect on many of the major organs of the body, including the respiratory, cardiovascular, musculoskeletal and gastrointestinal systems. According to Healthy Aging, people who are old, chronically ill or otherwise not in good health are particularly susceptible to the effects of immobility, but anyone who is confined to bed rest for a long period may begin to suffer ill effects.
HCPro explains that many of the internal problems associated with immobility come from blood pooling in the lowest points in the body rather than circulating freely as it should. This can lead to complications such as blood clots and strokes as well as an increased pressure on the heart that can cause heart attack or edema. Another major change in the body's systems caused by immobility is a shift in the way the body processes food due to a lack of energy expenditure. This can lead to digestion problems and a serious decrease in appetite.
Finally, the musculoskeletal system is usually one of the first to begin to suffer damage from immobility, according to HCPro. Muscles reduce in mass and tone, and muscles and joints begin to feel stiff from disuse. Prolonged immobility can lead to muscles atrophying and severely restricting movement.