Allostatic load is a way of measuring how your body responds to stress. It looks at how well your body can handle strain and how it changes over time. For example, when you are under a lot of stress, your body needs to work harder to keep your heart rate and blood pressure in a safe range. Your body is responding to the stress by doing things like speeding up your heartbeat, releasing hormones, and tensing your muscles. Allostatic load is a measure of all of these things and how they change over time due to stress.