During the One Leg Stand (OLS) test, what must the subject do while standing on one foot?

During the One Leg Stand (OLS) test, the primary requirement for the subject is to maintain balance while counting out loud. This task serves multiple purposes: it tests the individual's ability to concentrate and perform two tasks simultaneously, which can be an indicator of impairment. While counting, the subject is required to stand on one foot, which inherently challenges their stability and coordination.

The act of counting also helps to quantify how well an individual is capable of maintaining balance under the additional cognitive load. This dual tasking is essential in the context of evaluating a person's sobriety, as those under the influence may struggle to complete both actions effectively. Thus, the focus on counting while balancing is critical to the test's design and intent.