The aim of this study was to compare the butterfly swimming speed during the insweep phase of two distinct arm pull patterns. Ten national-level swimmers (5 males with 17.5 ± 0.8-years and 5 females with 16.8 ± 0.9-years) were analyzed while performing butterfly all-out trials based on two distinct arm-pull patterns ("bent" and "straight"). The "bent" arm-pull refers to the stroke kinematics they use to swim. The "straight" arm-pull refers to a more extended elbow than they used to swim. Based on discrete variables, swimming speed was faster in the "straight" than the "bent" arm-pull, but not significantly (p = 0.546). Non-significant differences were also noted for the remaining discrete variables. Conversely, Statistical Parametric Mapping (SPM, continuous analysis) identified significant differences in swimming speed between ~42% and ~60% (insweep phase and the beginning of the upsweep phase; p = 0.001), and ~83% and ~87% (halfway through the release and recovery, respectively; p = 0.043) of the stroke cycle. SPM was more sensitive in identifying differences in swimming speed between arm pulls. Swimmers were faster while performing the "straight" arm pull than with the "bent" arm pull, predominately based on a faster swimming speed during the insweep phase.
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