What is physical deconditioning?
Physical deconditioning is a complex physiological process that occurs with prolonged bed rest or any chronic illness. It is particularly significant in patients who are suffering from autonomic dysfunction. This is because the autonomic dysfunction itself leads to exercise intolerance and then the lack of exercise can lead to a state of physical deconditioning and this can then potentiate the underlying autonomic problem. A few physical changes have been identified in patients who are “deconditioned”. One of these is that the heart becomes physically smaller. This means that every time the heart beats less blood is pumped around the body. In the resting state this will not have any major consequence. However, when a person in a deconditioned state then tries to exercise the heart has to work much harder to pump more blood around the body and this quickly leads to fatigue.
People who are very fit have a low resting heart rate- you will have heard of elite athletes having a heart rate in the 40’s (normal is considered 60-100). It is the parasympathetic component of the autonomic nervous system that generates this low resting heart rate. So when you are physically fit this means your parasympathetic function is strong and this is associated with health and reduced risk of heart attacks. When you are in a physically deconditioned state there is an imbalance between the sympathetic and parasympathetic components of the autonomic nervous system- sympathetic activity is increased and parasympathetic activity is decreased. This is the opposite of the fit athlete. It means that the resting heart rate will be much higher and any physical challenge will become much more difficult as the heart will simply have to work much harder to achieve the same goal as in someone who is physically fit. This state of physical deconditioning is reversible through a graded exercise programme.