A personal trainer is an individual who has gained a certification showing that they have achieved a level of competency for creating and delivering safe and effective exercise programs for apparently healthy individuals and groups, or those with medical clearance to exercise. They motivate clients by collaborating to set goals, providing meaningful feedback, and by being a reliable source for accountability. Trainers also conduct a variety of assessments beginning with a preparticipation health screening and may also include assessments of posture and movement, flexibility, balance, core function, cardio-respiratory fitness, muscular fitness, body composition, and skill-related parameters (e.g. power, agility, coordination, speed, and reactivity) to observe and gather relevant information needed to develop an effective exercise program and support client goal attainment. These assessments may be performed at the beginning of and after an exercise program to measure client progress toward improved physical fitness. They also provide education on many other aspects of wellness, including general health and nutrition guidelines. Helping clients reach their full potential in various aspects of life requires a comprehensive client-centered approach along with a belief that clients are resourceful and capable of change.

Qualified personal trainers or certified personal trainers (CPTs) recognize their own areas of expertise. If a trainer suspects that one of their clients has a medical condition that could prevent the client from safe participation in an exercise program, they must refer the client to the proper health professional for medical clearance.