INTRODUCTION In swimming evenly distributed movements are performed by the limbs. Nevertheless differences in the motion of the left and right body side are to be observed frequently. These effects are strongly related with breathing and lead to necessary correction movements, without a propulsion effect. A goal of the investigation was to quantify the energetic causes of these side differences. METHODS For the evaluation of the side differences we analyzed specific power tests for upper limbs of 1 or 2 min duration (freestyle/butterfly stroke) on a rope pulling ergometer. 82 tests (43 male and 39 female subjects) were included into our investigation.In addition 22 of the freestyle swimmers also participated in a three-dimensional trunk force test (Pegasus, BfMC Leipzig). RESULTS We found significant side differences in the dynamic parameters power, strength and maximum speed of both strokes.While the side differences in the butterfly stroke were generatedby differing stroke length, different stroke duration was the reason for the differences in freestyle stroke. The results of a trunk force test with the freestyle swimmers proved a significant correlation between the results on the rope pulling ergometer and the trunk strength in the frontal direction DISCUSSION The results show the relation of the higher dynamic parameters in the cyclic movement with a better stabilization of the trunk on the contra lateral side. This result stresses the importance of trunk muscles for the transmission of the generated momentums from the limbs to the overall system especially for freestyle sprinters. The conclusions for training practice of these results are a high-quality trunk muscle training as well as the control of an effective breathing technology in swimming.
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