Aim: The aim of the study was to analyze how varying kick frequency affects kinematic parameters (especially kick amplitude, wave velocity, swimming speed, etc.), and consequently, to determine whether higher swimming speeds are realized primarily increasing kick amplitude or kick frequency. Methods: Six fin swimmers swimming performing undulatory motion in a prone position were instructed to swim at maximum speed at a depth of about 0.9-1.1m below the water surface. Kick frequency was external paced by an acoustic signal produced by striking an underwater metal bar, ranging from 0.8Hz to 2.3Hz in steps of 0.3Hz. Swimmer`s motion in the sagittal plane was recorded using a high-speed camera with 125Hz positioned perpendicularly to the swimmer`s sagittal plane. LED markers attached to the swimmer`s anatomical landmarks (wrist, shoulder, hip, knee, ankle, toe, and fin) were semi-manual analyzed using WinAnalyze 3D 2.8.Results: Swimming speed increased with increasing kick frequency, whereas kick amplitude decreased. Thus, kick amplitude did not remain constant across frequencies but was reduced at higher frequencies. These findings suggest a possible interdependence between kick amplitude and kick frequency, although the direction of causality remains unclear.Conclusions: The results indicate that increases in kick frequency are the primary driver of higher swimming speeds. Therefore, kick frequency appears to play a more dominant role than kick amplitude in enhancing swimming speed during undulatory monofin swimming.
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