However, the purpose for this recommendation does not seem to be very clear. It seems that exercise is defined as or equated with any type of physical exertion and that this exertion will somehow confer functional improvement through some unknown mechanism. This approach has no logical or biological basis and has been proven ineffective. This does not mean that exercise is ineffective, nor should the search for an efficacious exercise protocol be abandoned. What we need are concrete goals for what we expect exercise to accomplish and this can only be done if we know how exercise helps in rehabilitation.
Rehabilitation literally means to restore ability or physical function.
Increasing overall physical function is the goal, but in order to restore or at least improve function, we must restore or at least enhance the physical structures that have been compromised from injury. Exercise can dramatically enhance physical function because it enhances bodily structures, especially those of muscle and bone. This physical enhancement occurs as a result of the body's adaptive response to exercise. In some cases, the level of physical adaptation can be enormous, and it is this effect that has profound benefits in the area of rehabilitation. However, to achieve this physical adaptation, exercise therapy must be applied in a specific manner.