Immobilisation post injury and surgery will lead to changes in physiology in the body. Due to a cumulative effect, prolonged hospilization can lead to a significant decline in functional capacity. Here are some reasons why physiology changes occur with induced inactivity but reversed with activity.
Hypomobility/ contracture- adaptive shortening of soft tissue structures skin, fascia, muscle etc.
Cartilage- articular cartilage requires load to maintain integrity. Being immobile leads to softening and fragmenting of cartilage surfaces leading to decreased comprehensive stiffness or increased deformity making it susceptible to injury.
Collagen- parallel alignment of type 1 collagen is crucial to function. With immobility there’s an oblique laying of new fibers, causing impaired strength and elasticity. Water and glycosaminoglycan content is decreased affecting mechanical strength and poor quality healing. Finally there’s excess fibrin deposited which leads to scar tissue formation.
Being immobile leads to a significant decrease in the rate of protein synthesis (this occurs during the 6th hour of immobilisation). Consequently there’s a decreased in the percentage of sectional fiber area, and slow twitch fibers. Postural muscles are the first area to atrophy.
The build up and breakdown of bone is proportionate to forces being applied. If forces aren’t applied, bone is rapidly absorbed, leading to increased osteoclastic activity and decreased rate of new bone formation. Not moving for 3 months can results in a 15% decrease in bone mineral density. Weight bearing bones are the first to lose mass; this is within the first few days.
This is only a snap shot as motor neuron activity, cardiovascular, pulmonary, psychological, dermatological can also be affected. So moral of the story is to keep moving!