1. Which systems of the body show physiologic changes following prolonged immobilization?

• The musculoskeletal system

• Cardiovascular system

• Autonomic nervous system

• The extra-cellular fluid compartment

• There are also changes in overall body composition of fat and protein

2. What are these changes in the overall body composition that you have mentioned?

• Reduction in the lean body mass: this is seen as an increase in the excretion of nitrogen after the 5th day of bed rest. The level of protein catabolism falls after several weeks, but is still higher than normal

• Increase of adipose tissue deposition: as a replacement for loss of muscle mass

• Increased potassium excretion: since this is the major intracellular cation and especially rich in muscle, loss of potassium is an indicator of loss of total body lean tissue mass

3. How long after continued bed rest are cardiovascular changes seen?

About three weeks.

4. What are these changes?

• Increase in heart rate: after three weeks, the rate increases about half a beat per minute per day of immobilization

• Reduction of stroke volume: this is associated with a measure of cardiac atrophy

• CO and arterial pressure are maintained: owing to the conflicting changes above

• Adaptations to postural changes are impaired: this is because of impairment of the inotropic and CO response to a fall in the arterial pressure, despite an exaggerated peripheral vascular response. There is also a reduction in the overall activity of the ANS, leading to a blunting of cardiovascular responses

5. What happens to the musculoskeletal system following three weeks of bed rest?