Introduction: Athletic performance is the result of the interaction of various factors. The flexibility of the joints plays an important role in athletic performance. The effect of static and dynamic stretching on physical performance has been studied, but with no mention to variable duration. This study aims to examine the effect of duration of acute static and dynamic stretching on sprint performance, in terms of speed and flexibility. Methods: Seventeen football players (mean age 15.9±0.8 years) participated in the study. All performed three static stretching protocols and three dynamic stretching protocols with variant duration, in six different training days with random order. The static and dynamic stretching protocols, lasting 20 seconds each, were performed in three different sets of repetition: 1x20 sec (volume 20 s), 2x20 sec (volume 40 s) and 3x20 sec (volume 60 s). Range of motion was determined during hip flexion, extension and abduction, knee flexion and ankle dorsiflexion using a goniometer. Five pairs of photocells at various distances (0 m, 5 m, 10 m, 20 m and 30 m) were used for speed evaluation. Results: Sprint performance remained unchanged at the whole distance of 30 m after dynamic stretching for 20, 40 and 60 s. Static stretching for 40 and 60 s the sprint performance decreased (p<0.05), while it remained unchanged for the first 20 meters (m) and decreased in the last 10 m, when the stretching duration was 20 s. Independently from duration static and dynamic stretching increased joint flexibility. Conclusion: The findings indicate that dynamic stretching does not influence sprint performance, independently of the duration (20-60 s). However, static stretching performed for more than 20 s (40-60 s) seems to decrease sprint speed. Both static and dynamic stretching improves joint flexibility, in a way irrelevant to duration. Level of evidence: IIa.