Physiological reserve is your body's ability to tolerate and recover from stress, illness, and injury. The concept becomes increasingly important with age. Although many people focus on preventive care, immunizations, avoiding colds and flu, or preventing pneumonia, it is often low physiological reserve that places them at risk for poor outcomes, including death. Treating an illness with antibiotics, for example, addresses only pary of the problem. Even if treatment is successful, the body must still clear infection and inflammation and repair damaged tissue. Someone with a low physiological reserve may not have enough capacity to recover and survive. Do you or someone you care for have enough reserve to fight a serious illness? Building muscle mass, improving cardiovascular and pulmonary capacity, maintaining good nutrition, strengthening immune function, preserving mobility, preventing deconditioning, and supporting mental health all contribute to physiological reserve. Small, consistent gains -- not exceptional performance - can significantly improve survival from illnesses that otherwise carry high risk of fatality.