Final answer:
At rest, normal oxygen unloading is approximately 97%, indicating most of the oxygen remains bound to hemoglobin after circulating through the body.
Step-by-step explanation:
At rest, normal oxygen unloading is ~97%. This refers to the percentage of oxygen that remains bound to hemoglobin after it has passed through the body's systemic circulation and has delivered oxygen to tissues. Typically, hemoglobin in arterial blood is about 97% saturated with oxygen.
As it circulates through the tissues, some of the oxygen is released to meet the metabolic needs of the cells. However, at rest, a majority of the oxygen remains bound to the hemoglobin, which then returns to the lungs to pick up more oxygen during the process of external respiration.