23 The aim of this study was to assess the impact of a 6-week specialized training program aimed at 24 strengthening core muscles to improve the effectiveness of selected elements of a swimming race in 25 group of elite polish swimmers. Sixteen male national and international level swimmers (21.6 ± 2.2 26 years) participated in the research. The competitors were randomly assigned to 1 of 2 groups before 27 the data collection process: an experimental (EG, n = 8) and control (CG, n = 8) group. Both groups 28 of swimmers carried out the same training program in the water environment (volume and intensity), 29 while swimmers from EG additionally carried out the specific core muscle training. The task of the 30 swimmers was an individual swim of 50 meters freestyle, during which the kinematic parameters of 31 start, turn and swimming techniques were recorded using the video camera system. In both groups a 32 minor increase in the flight phase was observed during the start (EG=0.06 m, 1.8%; p=0.088; CG = 33 0.08 m, 2.7%; p=0.013). The time of the distance 5 m after the turn and the recorded average speed 34 of swimming this distance in EG statistically significant improved accordingly 0.1 s (-28.6%; 35 p<0.001) and 3.56 m•s -1 (23.2%; p=0.001). In EG, a statistically significant improvement in 50-m 36 freestyle performance was observed by 0.3 s (-1.2%, p = 0.001). The results of the research show that 37 the implementation of isolated strength of the stabilizing muscles seems to be a valuable addition to 38 the standard training of swimmers. 39 40