The relationship between current spot (or forward, for forward barriers) and the barrier price of an option. It is expressed as the percentage difference between the spot (or forward) and the trigger. It can also be defined as the wealth of the trigger portion of the option, taking into account the bias of the trigger.

Health = [(current spot or forward/ barrier price)- 1] × 100

Health is a measure of the execution risk as it allows traders to foresee an approaching execution. Typically, a warning flag comes up when that number drops below 1 standard deviation. Most of the time, health corresponds to the difference between current spot and the barrier price. Forward knock-ins and knock-outs are very rare as options do not knock in or out at the forward.