A personal trainer is a fitness professional 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 may also educate their clients in many other aspects of wellness besides exercise, including general health and nutrition guidelines. Qualified personal trainers recognize their own areas of expertise. If a trainer suspects that one of his or her 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.
Purpose of personal training 
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. The decision to hire a personal 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 personal trainer pays close attention to their client's exercise form, workout routine, and nutrition plan.
Few studies have investigated personal training for men. Personal training in 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). Personal training results in higher strength, higher workout intensities, and higher perceived exertion during exercise in women. Although women working with personal trainers do self-select heavier loads than women who did not, the loads used are still below recommended training load percentages.
Employment characteristics 
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, 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.
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. Personal trainers may also be involved in prescription of stretching routines or other approaches. 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.
Personal trainer accreditation is a process that provides certification of competency as a personal trainer. Qualification standards for personal trainers vary between countries.
In Australia, personal trainers are required to be a member of a registering body (Fitness Australia or Kinnect) to gain insurance and work as a personal trainer. The minimum qualification is a 'Certificate IV' in Fitness, and they 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.
In Canada, the main certifying bodies are Canadian Fitness Professionals, Certified Personal Trainers Network, and Canadian Society of Exercise Physiology. CSEP requires a diploma or degree in the exercise field, most require experience and/or workshops. 
United Kingdom 
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 a 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. 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.
United States 
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.
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:
- 70% of those surveyed did not have a degree in any field related to exercise science.
- Those who did not have a bachelor's degree in exercise science-related field scored 31% less on average than those with a bachelor’s degree or higher in the field.
- Those holding one of three specific certifications (the American College of Sports Medicine (ACSM), the International Sports Science Association (ISSA) or the National Strength and Conditioning Association (NSCA)) certification scored 83% of the questions correctly on average. Those holding any certification other than ACSM or NSCA answered only 38% of the questions correctly.
- Years of experience was not found to be predictive of personal trainer knowledge.
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) or an equivalent organization. IHRSA considers other accreditation|accreditation agencies if recognized either by the Council for Higher Education Accreditation (CHEA) and/or the U.S. Department of Education (USED). The National Personal Training Institute is the only 500-hr Diploma program approved by the state Board of Education in 32 states. As of August 2012, NASM, ISSA, ACSM and NSCA certifications are among the 15 accredited certifications recognized by IHRSA, three of which are accredited by an agency other than NCCA (the Distance Education Training Council (DETC)).
There remains no national legal restriction on the industry to date.
World Instructor Training Schools (WITS) is the only personal fitness trainer certification course accepted for 3 collegiate health credits through the American Council on Education (ACE).
- Earle, Roger (2004). NSCA's Essentials of Personal Training. NSCA Certification Commission. pp. 162, 617. ISBN 0-7360-0015-1.
- Kraemer, WJ. Exercise Physiology: Integrating Theory and Application. Lippincott Williams & Wilkins. Ahead of print, March 2011.
- Fischer DV, Bryant J. Effect of certified personal trainer services on stage of exercise behavior and exercise mediators in female college students. J Am Coll Health. 2008 Jan-Feb;56(4):369-76. PMID 18316279.
- Ratamess NA, Faigenbaum AD, Hoffman JR, Kang J. Self-selected resistance training intensity in healthy women: the influence of a personal trainer. J Strength Cond Res. 2008 Jan;22(1):103-11. PMID 18296962.
- Kraemer, WJ. Exercise Physiology: Integrating Theory and Application. Lippincott Williams & Wilkins. Chapter 12. Ahead of print, March 2011.
- "Top Personal Training Certifications: Canada". Retrieved 29 March 2013.
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- Moh H. Malek, PhD, CSCS,*D and Tamara K. Coburn. The Level of Exercise Science Knowledge Among Personal Fitness Trainers: A Guideline. .