There is scarce information about what characterizes the swimming speed in the butterfly
stroke and the role of thrust in its characterization and prediction. The aim of this study was
to compare the fastest and poorest butterfly swimmers based on a set of anthropometric,
kinematic, and kinetic variables and to identify the swimming speed predictors. Eight
young male swimmers were divided into two equal groups (each group comprising four
swimmers). The swimming speed, as well as a set of anthropometric, kinematic, and kinetic
variables, were measured. The swimming speed presented significant differences between
the groups (p = 0.011, d = 2.18). The stroke frequency (kinematics, p = 0.027, d = 1.69)
and thrust (kinetics, p = 0.034, d = 1.57) also presented significant differences between
the groups. The swimming speed presented significant correlations with the stroke index
(rs = 0.83, p = 0.011) and thrust (rs = 0.83, p = 0.011). The swimming speed was predicted
by a combination of the stroke frequency and thrust (R2 = 0.84, p = 0.010). Coaches and
athletes must be aware that combining fast stroke frequencies and the generation of greater
thrust leads to the fastest swimming speeds.
