INTRODUCTION: For effective propulsion the resultant force produced by a swimmer`s hand should be aimed as much as possible in the swimming direction (Toussaint et al., 2000). Moreover, it is suggested that in-water resistance training methods, such as sprint-resisted swimming, would be more effective for the improvement of the swimming performance. However, there is a lack of data regarding the acute effect of the sprint-resisted swimming on the direction of the resultant force of the hand, which was the aim of the present study. METHODS: Five female swimmers swam 25 m front crawl with maximal intensity, without and with added resistance. A bowl with a capacity of 6 l was used as added resistance. The underwater motion of the right hand was recorded using 4 cameras (60 Hz) and selected points were digitized using the Ariel Performance Analysis System. The hydrodynamic coefficients and the methodology presented by Sanders (1999) were used for the estimation of the drag, the lift and the resultant force of the swimmer`s hand. Moreover, the angle between the resultant force and the axis of propulsion was calculated. For the statistical treatment of the data the t-test for dependent samples was used. RESULTS: During resisted swimming the magnitude of the drag, the lift, the resultant and the effective propulsive forces were not altered significantly. However, the angle between the vector of the resultant force and the axis of swimming propulsion in the pull phase was decreased significantly (t4= 2.877, p< 0.05) during resisted swimming (13.26 ± 15.37 deg), in comparison with free swimming (36.31 ± 14.73 deg). DISCUSSION: During sprint-resisted swimming, the angle formed between the resultant force vector and the axis of the swimming propulsion was decreased significantly in the pull phase and thus the resultant force was steered more in the forward swimming direction. Consequently, it could be speculated that front crawl sprint-resisted swimming probably could contribute to the learning of a more effective application of the propulsive forces.
© Copyright 2010 Biomechanics and Medicine in Swimming XI. Published by Norwegian School of Sport Sciences. All rights reserved.