A personal trainer is an individual certified to have a varying degree of knowledge of general fitness involved in exercise prescription and instruction. They motivate clients by setting goals and providing feedback and accountability to clients. Trainers also measure their client's strengths and weaknesses with fitness assessments. These fitness assessments may also be performed before and after an exercise program to measure their client's improvements in physical fitness. They should also educate their clients in many other aspects of wellness besides exercise, including general health and nutrition guidelines. It is very important that a trainer takes their time to evaluate a clients personal life outside of the gym. This way, personal trainers can figure out what kind of stress their client may be putting on certain areas of the body during their every day lives.

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 prior clearance.^[1]

The scope of practice for a personal trainer is to enhance the components of fitness for the general, healthy population.

Proper exercise prescription may result in improved body composition, physical performance, heart condition and health outcomes.^[2] The decision to hire a trainer may be related to a perceived ability to facilitate these factors through proper prescription and instruction or factors related to motivation and adherence. A trainer pays close attention to their client's exercise form, workout routine, and nutrition plan. Personal training in men and women has been shown to exercise behavior patterns, improve perceptual benefit-to-concern ratio for exercise (decisional balance), and increase confidence to choose exercise in the face of other time demands (scheduling self-efficacy).^[3] Personal training results in higher strength, higher workout intensities, and higher perceived exertion during exercise.

The profession is generally not restricted by venue, and personal trainers may work in fitness facilities, in their personal homes, in client homes, over live video (also called "virtual personal trainers"),^[4] or outdoors.

Almost all personal trainers and group exercise instructors work in physical fitness facilities, health clubs, and fitness centers located in the amusement and recreation industry or in civic and social organizations.^[5] Personal training is not regulated in any jurisdiction in the United States except for Washington D.C. which adopted registration requirements for personal fitness trainers in February 2014.^[6] Some employers, such as gyms require personal trainers to be certified. However, this is not always the case and some personal trainers are able to find work without certification. Overall, personal trainers must possess certain skills, such as a passion for fitness and helping others achieve their goals, industry knowledge, leadership, and the ability to communicate effectively with their clients.

Personal trainers may specialize in a certain training type, training philosophy, performance type, exercise modality, or client population.

In general, most personal trainers develop exercise prescription plans for aerobic exercise, resistance exercise, and/or flexibility training. With aerobic exercise prescription, personal trainers determine the type of exercise, duration of exercise, and frequency of exercise. For resistance exercise prescription, the type of exercise, total session volume, rest period, frequency, and intensity are determined.^[2] Personal trainers may also be involved in prescription of stretching routines or other approaches. Personal trainers help clients to perform exercises with correct technique, minimising the risk of injury. While some discuss nutrition, ergogenic supplementation, and spiritual practices with clients, there is debate within the industry as to whether it fits within their scope of practice and training qualifications.^[8]

Personal trainer accreditation is a process that provides certification of competency as a personal trainer. Qualification standards for personal trainers vary between countries.

The International Confederation of Registers of Exercise Professionals (ICREPs) is an international partnership between registration bodies around the world that register exercise professionals.

Member countries conform to the international standards set by ICREPs for personal training (and other exercise education credentials) and are transferable to other member countries.

The current members of ICREPs (as of 2019) are: Fitness Australia, NFLA Canada, REPs India, REPs Ireland, REPs New Zealand, REPs Poland, REPs South Africa, REPs United Arab Emirates, REPs United Kingdom, and US REPs.

In Australia, personal trainers may work independently with suitable insurance or choose to be a member of a registering body (Fitness Australia or Physical Activity Australia).

The qualifications levels include; Level 1 - Certificate III in Fitness, Level 2 - Certificate IV in Fitness and Level 3 - Diploma of Fitness.

These can be obtained from nationally accredited colleges (TAFE, Australian College of Sport & Fitness, Fitness Industry Training, Global Fitness Institute, Australian Institute of Fitness, Australian Fitness Academy). Once working in the industry, trainers who are members of associations are also required to complete short courses to obtain continuing education credit (CEC) points they need to keep their registration. A minimum of 20 CEC points every two years is required. Many personal trainers also have additional qualifications in weight loss, strength training, kid's fitness, and nutrition, which is in part due to the CEC program. CEC courses can cover a wide variety of topics such as different training techniques, nutrition, exercise styles, health conditions, physiology, lifestyle and rehabilitation.^[9]

In Brazil, personal trainers must have a bachelor's degree in "Physical Education" (a degree that combines knowledge in the fields of Exercise Science and Healthcare science) and be registered with the Conselho Federal de Educação Física (Federal Council of Physical Education), and risk criminal charges if they operate without these two requirements.

In Canada the main certifying bodies are Canadian Fitness Education Services (CFES), Canadian Fitness Professionals (CanFit Pro), Certified Personal Trainers Network, the Canadian Society of Exercise Physiology (CSEP), and the National Fitness Leadership Association (NFLA).

CSEP requires a diploma or degree in the exercise field, most other organizations require experience and/or workshops to qualify for a credential.^[10][11] Many personal trainers receive a CFES, CanFit Pro, NFLA or an NCCA accredited certification, but there are no certifications required by law. Fitness instruction in Canada is an unregulated industry.

In Europe, personal trainers may work independently, but will always need accreditation by one of the main certifying bodies such as:

NASM: National Academy of Sports Medicine. NASM Certified Personal Trainers are eligible to join the European Register of Exercise Professionals (EREPS). The NASM has attributed to the success of personal trainers in Europe and accredited companies like UNITEDFIT in the Netherlands became recognized as a qualified fitness organization in Europe.

EREPS: The European Register of Exercise Professionals (EREPS) is an independent process for the registering of instructors, trainers and teachers working in the European health, fitness and physical activity sector. It is a pan-European system, based on independent national registers, which culminate in a central European database.

In the UK, there are several ways to achieve a personal training qualification.

Most personal training qualifications are accredited through awarding bodies like CYQ (Central YMCA Qualifications), Active IQ (Active International Qualifications) and City and Guilds.

These qualifications are generally delivered by Further Education (FE) establishments like colleges, or by private training providers. Upon successful completion of an accredited awarding body qualification, candidates become eligible for Level 3 REPs(Register of Exercise Professionals)status. University graduates with an appropriate honours degree can also apply to become an approved by REPs through Accreditation of Prior Learning (APL) and Accreditation of Prior Achievement (APA).

REPs is the professional body for the UK health and fitness industry, and does not award qualifications directly.

Most health and fitness qualifications endorsed by REPs vary in levels from 1 - 5, 1 being basic GCSE level and 5 being advanced specialized training professionals.^[12] For a qualification to become eligible for endorsement by REPs, it must conform to the National Occupational Standards (NOS), which are set at governmental level by the Sector Skills Council (SSC) Skills Active.

There is no legal restriction on the title of Personal Trainer nor any formal body associated with regulating Personal Training.

A number of certifications are available in the U.S., although a number are not accredited.

Most require a high school diploma, cardiopulmonary resuscitation (CPR) and automated external defibrillator (AED) certification, and some type of examination.^[5]

A 2002 investigation evaluated a random sample of 115 personal trainers using the Fitness Instructors Knowledge Assessment (FIKA) (which measures knowledge in nutrition, health screening, testing protocols, exercise prescription, and special populations).

The study described that:^[13][14]

In partnership with the fitness industry, the International Health, Racquet & Sportsclub Association (IHRSA), which represents over 9,000 health and fitness facilities, started an initiative in 2002 to improve standards for both its own clubs and the industry as a whole.

In January 2006, IHRSA implemented a recommendation that its facilities only accept personal trainers with certifications recognized by the National Commission for Certifying Agencies (NCCA) if recognized either by the Council for Higher Education Accreditation (CHEA) and/or the U.S. Department of Education (USDE). As a result, the Distance Education and Training Council (DETC) was recognized by IHRSA as a recognized accreditor of fitness professional certification organizations. Since then, the DETC has accredited several personal trainer certification organizations, including the Aerobics and Fitness Association of America (AFAA) and the International Sports Sciences Association (ISSA) among others. As of August 2012, NASM, ISSA, AFAA, ACSM and NSCA certifications are among the 15 accredited certifications recognized by IHRSA, three of which are accredited by the Distance Education Training Council (DETC).^[15][16]

Various organizations within the profession have lobbied for the adoption of a more stringent criteria for certification developed by the NSF International.^[16] There remains no national legal restriction on the industry to date except for the District of Columbia (D.C.) which as of February 2014, passed legislation requiring personal fitness trainers to register in that jurisdiction. The law went into effect in the first half of 2014.