3D underwater hand path patterns in butterfly swimmers

Abstract

The purpose of this study was to characterize underwater path patterns of the hand in a group of butterfly swimmers in non-breathing cycles in order to identify predictors of swimming velocity. Eight Portuguese international level male swimmers participated in this study (age: 18.75 ± 4.02 years, height: 179.50 ± 9.36 cm, body mass: 69.59 ± 6.66 kg, best time at 100m butterfly long course: 59,19 ± 3,15s), four of them competing at a junior age-group level. Each subject performed a maximal sprint of 50m butterfly, in a 50 m pool. Swimmers were asked to retain breathing after passing the 25m mark until the two final stroke cycles. Oblique underwater front views from below and from both sides were taken by two fixed digital and two other fixed digital cameras were positioned on the pool deck, one in front and one lateral in order to film the swimmers above the water. Images were retained for 3D kinematical analysis (APAS). The average intracycle horizontal speed (SS) of body centre of mass (CM) was used as the dependent variable. The underwater arm stroke patterns found matched those described by the literature. Both horizontal and vertical velocity components of the underwater path of the hands showed to influence the SS. The fastest swimmers displayed an anteroposterior component in the hand path during the outsweep, accompanied by a higher flexion of the elbow during this phase. Mean intracycle swimming velocity was related to horizontal velocity of the body CM during the upsweep. In this phase, the anteroposterior displacement of the hand path and the hand horizontal velocity showed significant correlation with swimming velocity (r= 0.820, p≤0.05 and r=0.890, p≤0.01, respectively). In this group of swimmers, an early catch and a more pronounced horizontal velocity of the hand in the upsweep, both denouncing a drag oriented propulsive pattern of the hands, seem to be related with better performances in butterfly sprint swimming.