Morais, J.E.Marinho, D.A.Barbosa, Tiago M.2024-02-272024-02-272024Morais, J.E.; Marinho, Daniel A.; Barbosa, Tiago M. (2024). Measurement of the active drag coefficient in front-crawl: a stroke-by-stroke analysis. Journal of Biomechanics. ISSN 0021-9290. 164, p. 1-5http://hdl.handle.net/10198/29592The purpose of this study was to understand the change in active drag coefficient (CDA) over successive stroke cycles in front-crawl and the relationship between swimming speed and CDA. Eighteen national competitive swimmers (nine girls and nine boys with a mean age of 14.91 ± 0.59 years) were recruited. Swimming speed, propulsion (Ftotal) and frontal surface area were measured to calculate the CDA. Swimming speed (F = 1.790, p = 0.182, η2 = 0.07) and CDA (F = 0.907, p = 0.413, η2 = 0.06) did not change significantly over time, but swimming speed showed a decrease between the second and third stroke cycle. On the other hand, the Ftotal changed significantly over time (F = 4.437, p = 0.019, η2 = 0.21). Swimming speed and CDA showed a linear and strong relationship (R2 = 63.8 %). A stroke-by-stroke analysis showed that national level swimmers were able to maintain their hydrodynamic profile during a front-crawl maximal trial. Thus, it can be argued that a decrease in swimming speed can be related to a decrease in Ftotal. Swimming speed and CDA showed an inverse and significant relationship, with lower values of CDA resulting in faster swimming speeds.engSwimmingHydrodynamicsTechniqueTrainingPerformancejournal article10.1016/j.jbiomech.2024.1119931873-2380