The energetic component of the ion distribution function in the core of fusion plasmas is known to have a strong effect on sawtooth stability. Stabilising effects can lead to the occurrence of long sawtooth periods where the crash may be triggered as a result of a sudden depletion of fast ions from the core due to other instabilities. For example, particle losses due to fishbone activity have been observed just prior to sawtooth crashes. The detailed time evolution of the fast particle distribution throughout the sawtooth cycle is therefore of considerable interest.