Background: To learn how to swim with proper technique takes fairly large amount of time and practice to learn and anelite swimmer spends 6-7 days training for improving aerobic capacity, anaerobic capacity and strength training for energy saving technique. Freestyle is the fastest swimming style and is performed in many different distances, 50m is classified as a sprint and the 400m as a middle-distance. The research is inconclusive if there is a correlation in the lower body and the time in 50m and 400m and mostly in the middle distance which gives this study the importance reducing these uncertainties. Aim: The aim of this study was to determine the strength of the correlation between the upper- and lower body muscle strengthwith time in 50m and 400m freestyle and to analyze which of the variables of height, sex, upper- and lower body strength contribute to velocity in sprint and middle distance in competitive swimmers. Method:A total of 14 participants (3 men and 11 women) participated in the study. The participants were tested at three occasions. The first was to determine their three-repetition maximum (3RM) in the squat and lat-pulldown. The second occasion was the collection the time in 50m freestyle and the third was to collect the time in 400m freestyle. Relative strength (kg/kg BW; %) and absolute strength (kg) in 1RM was calculated and correlated with the time in 50m and 400m freestyle. Analysis was done to see which variables of height, sex, relative strength in the squat and lat-pulldown contribute the most to the time in freestyle. Result: The result show that there was a high correlation between the absolute strength in the squat and the time in 50m (r=-0.769) a moderate correlation in the absolute strength in lat-pulldown and the 50m freestyle sprint (r=-0.513). There was also a moderate correlation for the relative strength in the lat-pulldown and 50m freestyle (r=-0.599). The 400m correlate with the relative strength in both lat-pulldown(r=-0.563) and the squat (r=-0.555). The lat-pulldown contributed most to the time in 50m freestyle as well as the male sex. Conclusions: The absolute strength in the squat had a high correlation to the time in 50m freestyle swim. The 400m there was a moderate correlation to the relative strength in the squat and lat-pulldown showing that for the overall performance in middle-distance the relative strength has the advantage over absolute strength. The relative and absolute strength in upper body correlated to both 50m and 400m freestyle and could therefore strengthen the importance of upper body strength in sprint and middle distance as previous researchers has stated. The upper body strength is the best predictor of time in 50m.