Each individual athlete has a different level of fitness and experience. The length of time an athlete has been training will affect their fitness level and capacity for work. Training age must be considered and is simply the number of years an athlete has trained for athletics or an athletics-related activity. The importance of knowing an athlete’s training age was emphasised in the chapter on ‘Developing the Athlete’. It is not possible to know the appropriate stage of development without knowing an athlete’s chronological age, biological age and training age. Without knowing the athlete’s stage of athlete development it is not possible to plan appropriate training. The following table helps to explain the importance of considering biological and training ages as well as chronological age.Athletes of the same chronological age, but different stages of athlete development and very different capacities for training.In the second situation shown in the next table, the athletes’ capacities for work may be similar, but the individual responses to training will still need to be considered.Athletes of different chronological ages, but same stage of athlete development and similar capacities for training.