Morais, J.E.Costa, M.J.Forte, PedroMarques, Mário C.Silva, A.J.Marinho, D.A.Barbosa, Tiago M.2015-01-212015-01-212014Morais, J.E.; Costa, M.J.; Forte, Pedro Miguel Gomes; Marques, M.C.; Silva, A,J,; Marinho, D.A.; Barbosa, Tiago M. (2014). Longitudinal intra- and inter-individual variability in young swimmers' performance and determinant competition factors. Revista de Educação Física. ISSN 1980-6574. 20:3, p. 292-3021980-6574http://hdl.handle.net/10198/11616The main purpose of this study was to follow-up the intra- and inter-individual variability of young swimmers’ performance and determinant factors over two competitive seasons. Thirty young swimmers (14 boys: 12.33±0.65 years -old; 16 girls: 11.15±0.55 years-old) were followed-up throughout two consecutive seasons (seven evaluation moments). Performance (100m freestyle), anthropometric, kinematic, hydrodynamic and efficiency features were evaluated. A gender and skill-level effect was observed. Boys improved in a higher amount (%) comparing to girls. Overall, swimmers in skill-level 2 (both genders) presented a higher intra-individual variability. Performance and anthropometrics showed a significant inter-individual variability in most moments, but hydrodynamics, kinematics and efficiency did not. Within each skill-level hydrodynamics, kinematics and efficiency were the variables that showed a high inter-individual va- riability. As a gender and skill-level effect was noticed in an age-group of young swimmers, coaches and practitioners should put the focus in specific and customized training plans for each skill-level of swimmersengYoung swimmersSeasons' variationsEfficiencyStroke mechanicsAnthropometricsjournal article10.1590/S1980-65742014000300008