With the above in mind, you should first understand that sports psychology is really an interdisciplinary science. Besides psychology, it is also concerned with disciplines such as biomechanics, physiology, and kinesiology. As a definition, the American Psychological Association’s Division 47 (Society of Sport, Exercise, and Performance Psychology) states the following:
Once you are in a sufficiently suggestable state the hypnotherapist will then start their specific stop smoking session to try and change the way you think about your relationship with tobacco. These usually are based around visualization techniques. For example you may be asked to visualize what it would be like to suck on a car exhaust, or you may be asked to imagine the amount of ash you have inhaled over your lifetime in a big pile.
Exercise psychology and sport psychology involve the scientific study of the psychological factors that are associated with participation and performance in sport, exercise and other types of physical activity. Sport psychologists are interested in two main areas: (a) helping athletes use psychological principles to achieve optimal mental health and to improve performance (performance enhancement) and (b) understanding how participation in sport, exercise and physical activity affects an individual's psychological development, health and well-being throughout the lifespan.
The link between exercise and psychology has long been recognized. In 1899, William James discussed the importance of exercise, writing it was needed to "furnish the background of sanity, serenity...and make us good-humored and easy of approach." Other researchers noted the connection between exercise and depression, concluding a moderate amount of exercise was more helpful than no exercise in symptom improvement. Additionally, meeting exercise requirements can also aid in alleviating symptoms of avoidance disorders and anxiety, while also providing a higher quality of life for the patient in terms of physical health. 
It is used for a wide variety of applications, and studies into its efficacy are often of poor quality which makes it difficult to determine efficacy. Several recent meta-analyses and systematic reviews of the literature on various conditions have concluded that the efficacy of hypnotherapy is "not verified", that there is no evidence or insufficient evidence for efficacy.