Deconditioning refers to which of the following?

Deconditioning specifically refers to the physiological decline in muscle strength and cardiovascular fitness that occurs as a result of prolonged inactivity or immobility. When an individual is less active, whether due to illness, injury, or other factors, their muscles can weaken, and their overall physical condition deteriorates. This loss of strength makes it more difficult for the individual to perform everyday activities and can lead to further health complications.

In contrast, the other options describe different concepts. Movement toward the midline of the body aligns with the anatomical term "adduction"; joint immobilization pertains to the restriction of motion in a joint, which is a separate issue that does not necessarily involve a loss of strength; and creating muscle tension refers to the physiological process of engaging muscles, which is unrelated to the effects of inactivity. Thus, the definition of deconditioning as a loss of muscle strength from inactivity is accurate and reflects the primary concern of health professionals regarding sedentary lifestyles or recovery from illness.