Recently, within the borders of a Marie Curie IEF project, we have established zebrafish as a novel exercise model and demonstrated the stimulation of growth by exercise in adult zebrafish (Palstra et al., PLoS ONE, 2010). Exercise may also induce hypertrophy and cardiomyocyte proliferation in zebrafish making it an important model to study vertebrate heart regeneration and improved robustness of fish in aquaculture. Moreover, zebrafish has been recently recognized as a valuable model for immunological studies since they possess an adaptive and innate immune system similar to mammals. Given the beneficial effects of exercise on mammalian immune function, zebrafish can be used to investigate exercise-induced stimulation of immune function.In this project we propose to use this novel exercise model for human and fish and, by applying state-of-the-art techniques, to demonstrate the mechanisms behind the beneficial exercise effects of enhanced skeletal and cardiac muscle growth and immune functioning, and to exercise glucocorticoid knock out and transgenic zebrafish to assess the role of the cortisol stress response at the base of these beneficial exercise effects.SWIMFIT will enable the development of a novel research line on exercise integrating the applicant’s existing expertise on exercise physiology with applying high throughput genomic, transcriptomic and proteomic methodology thereby creating a new scientific niche.At the Institute for Marine Resources and Ecosystem Studies (IMARES) of the Wageningen University, the applicant has postulated a position as researcher aquaculture and is investigating the opportunities for implementation of exercise in aquaculture. Besides these applied studies, this Marie Curie reintegration grant would offer the opportunity to deepen the initiated fundamental studies on zebrafish to demonstrate the functional mechanisms behind the beneficial effects of swimming using all the advantages that zebrafish offers as a model fish.