Continuum therapists conduct Physical Demand Analysis (PDA) to evaluate the essential and non-essential tasks in a job including measurement of the physical, environmental, and cognitive / perceptual components of a job. In addition, environmental conditions, work pace, and psychosocial factors within the workplace are considered. Assessment involves the direct observation of the job being performed, a comparison to available job descriptions for that job, subjective reports from workers and management, and a review of similar positions found in the National Occupational Classification (NOC). A PDA can help determine if a job is suitable for a worker, or if modifications or alternate work are required to assist in return to work planning. PDAs also help identify safety risks within a position to assist in injury prevention programs.