In Sports (athletics) records are broken regularly. Improvements in performance are a result of better science-based training. Higher levels of fitness in particular the understanding by coaches of the process and effects of training is also a key factor of an improved athletes’ performance.
What is fitness
One’s capacity to perform work (exercise) of a specific intensity and duration; may be aerobic, anaerobic, or muscular.” Anshel: Dictionary of the sport and exercise sciences, p. 60
How well a person is adapted to the performance determining factors of the event(s).The athlete needs to be fit for the demands of his sport/event (specificity).
What is training
Any program of exercises designed to improve the skills and increase the energy capacities of an individual for a particular activity; adaptations that occur are specific to the system […] loaded. Anshel: Dictionary of the sport and exercise sciences p. 154