5: Immobility

INTRODUCTION

Immobility is the enemy of function. Much of physiatric treatment revolves around movement and its antithesis, immobility. This concept applies equally to generalized immobility (progressive functional decline in senior citizens as a result of cumulative effects of pain, fear of falling, and muscle weakness), forced immobility (bed rest during hospitalization or experienced by astronauts in microgravity), and immobilization of discrete body parts (range-of-motion [ROM] restriction caused by spasticity, contracture, or splinting or casting of fractures).

Rehabilitation marshals the body’s ability to change, adapt, and grow in response to stimuli. This is as true for neuroplasticity in a stroke patient as it is for strengthening of the rotator cuff muscles in a patient with chronic tendinopathy. Immobility is not a null state in which bodily functions remain in physiologic equilibrium. Like movement and exercise, immobility is also a condition that stimulates physiologic adaptation, leading to rapid changes in cardiovascular, pulmonary, musculoskeletal, and neurologic function that ultimately decrease our ability to interact with the world around us. The cause and effects of immobility in patients should always be examined and reexamined. These factors have great bearing on an individual’s function, independence, safety, and emotional well-being.

BED REST & IMMOBILIZATION

Throughout the history of medicine, enforced immobilization or bed rest has been a staple of treatment for both illness and injury. Conditions that historically have been or currently are treated with enforced rest include acute low back pain, heart attack, tuberculosis, fracture, and critical illness (eg, sepsis).

Actual and theoretical justifications for bed rest include reducing metabolic demands of the body, thus “conserving” these resources for recovery. Reduction of oxygen consumption by muscles—both skeletal and cardiac—decreases oxygen demand by all tissues, resulting in less mechanical ventilation, lower Fio₂, and less risk of ventilator-induced lung injury. Other perceived benefits include decreased cardiac stress, improved central nervous system perfusion, bone healing, and pain control (eg, in the immobilization of an injured appendage for comfort). Additional perceived benefits apply to safety: maintenance of intravenous access and artificial airways, fall prevention, and prevention of occupational injuries to nursing staff.

Specialists in physical medicine and rehabilitation work in the borderland between mobility and immobility. Patients with spinal cord injury, neuropathy, stroke, or peripheral nerve injury with sensory impairment do not experience the same discomfort that would prompt a neurologically intact person to shift position or treat a wound or laceration. Physiatrists also treat patients who are protectively immobilized in splints or casts for fractures, ligament tears, or tendon injury. They often encounter and treat the effects of self-imposed or functional immobility of joints due to stiffness and pain.

MUSCULOSKELETAL CONSEQUENCES OF INACTIVITY

1. Weakness

Muscle mass drops by 1.5–2% per day in the first 2–3 weeks of bed rest. A muscle completely at rest therefore loses 10–15% ...