Background: Competitive swimming is a sport that require high muscle strength to overcome the forces in the water. A phenomenon called post activation potentiation (PAP) is known to acutely increase power output. PAP can be defined as an increase in muscle performance after muscle contraction. Previous research on PAP has shown positive effects on different sports, including swimming. However, a limited amount of studies exists on PAP associated with swimming and distances longer than 100 meters. Aim: The aim of the study was to investigate if PAP for triceps brachii and latissimus dorsi with elastic bands can improve the aerobic performance, V4-speed, of elite freestyle swimmers. Methods: 13 elite swimmers participated in this study (mean ±SD: age 18 ±1.15). The participants performed three test sessions on two different days. The first occasion evaluated aerobic performance, V4-speed, where the participants performed a 400-m freestyle swim race and lactate and time were collected. At the second occasion, a 10-repetition maximum (RM) elastic resistance band test was done to get the right resistance band for each individual participant for the PAP exercise. At the third occasion, a PAP exercise, that mimics freestyle swim, with elastic resistance band was performed with 10 repetitions in two sets. After, a rest of six minutes was performed and then the same 400-m freestyle swim test as the first occasion. A paired samples t-test was used to evaluate significant differences between the swim test performed with and without a PAP exercise. Results: The study showed no statistical difference between the V4-speed with or without PAP exercise (p=0.93). An increase in lactate was seen after the PAP exercise (p=0.02). Conclusion: This study could not ensure an improvement of the aerobic performance, V4-speed, of elite swimmers when a PAP exercise, similar to a freestyle stroke, was performed before a 400-m submaximal freestyle swim race with elastic resistance band. Further research must be done in this area before coaches and athletes can apply this in training programs.