Besides physiological and technical factors, power and speed play important roles in swimming performance. The main goal of this scientific research is to define the correlation between 8 different parameters obtained with tethered swimming and t50 freestyle. The second goal of this scientific research is to develop a computer software which calculates and analyses the pull swimming force obtained by a dynamometer. By accomplishing the two mentioned goals, it can be concluded which factor impacts more swimming performance, power or technique. Measurements are obtained on 8 professional swimmers of the Croatian Academic Sports Club Mladost using dynamometric probes. The measured forces are further analysed with a computer software. The method of correlation and multiple regression analysis, from the software package Statistica, is used to determinate the correlation between different force parameters during a swimming stroke and the sprint t50 freestyle. The results of the correlation analysis show a statistically significant correlation only between t50 freestyle and ImpF (p=0.716793), while multiple regression analysis showed no significant association. Low correlation is observed on other parameters including fatInd (p = 0,309155), RDF (p = -0,553791) and Fmax / kg (p = 0,346679). From the mentioned results it can be concluded that in short competition events it is not only important to produce the maximum force in the minimum time but to also use a technique which extends that force over the time and that the sample should be homogenized and larger.