The aim of this study was to examine the acute effect of backward running (BwR) during warm-up on a 20-m sprint of boys’ performance, compared to forward running (FwR). Fourteen recreationally active preadolescent boys (aged 12.5 ± 0.5 years) were examined in 3 protocols: warm-up (control condition), warm-up with 3 × 10 m additional BwR sprints and warm-up with 3 × 10 m additional FwR sprints. Participants were evaluated 4 minutes after each protocol on a 20-m sprint and intermediate distances, as well as the rate of perceived exertion (RPE). Sprint speed across 10-20 m was significantly higher for the BwR warm-up compared to the regular warm-up (p < 0.05) and a significantly higher RPE after the BwR and FwR protocols compared to the control condition was recorded (p < 0.05). No significant difference was detected across the distances 0–5, 5–10, 0–10 and 0–20 m. Although adding 3 × 10-m sprints of BwR or FwR after the warm-up did not enhance performance in a 20 m sprint of preadolescent boys, the positive effect of BwR across 10–20 m distance suggests that BwR could be an alternative means for enhancing performance for certain phases of a sprint for this age. However, preadolescent boys’ response to different sprint conditioning exercise stimuli and the optimization of rest time to maximize performance remain to be determined.

AIM: Forward and backward sprint are two types of locomotion commonly used in sports. The purpose of the present study was to examine the acute effect of two post-activation potentiation sprint protocols, including the aforementioned types of locomotion, in subsequent 20-m sprint performance (SP) and the possible fatigue caused by them in preadolescent boys. MATERIAL & METHOD: Fourteen recreationally active preadolescent boys (aged 12.49 ± 0.52 years) volunteered to participate in the study. Boys’ SP was evaluated randomly on three non-consecutive days. SP was evaluated 4 min after (a) a typical warm-up (3 min jogging and dynamic stretching), (b) the typical warm-up followed by 3 x 10 m forward sprint and (c) the typical warm-up followed by 3 × 10 m backward sprint. Τhe Microgate Witty Wireless Training Timer was used for the evaluation of SP and the 10-degree OMNI scale for the evaluation of the rate of perceived exertion. RESULTS: ANOVA with repeated measures indicated no statistically significant effect of protocol on the 0–5, 0–10 and 0–20 m SP (p > 0.05). On the contrary, it was found that the protocols in which 3 × 10 m forward or backward sprint was incorporated caused statistically significant greater fatigue than the control protocol (p < 0.001), without any differences between them. CONCLUSIONS: The implementation of three 10-m sprints, either forward or backward, to a standard warm-up does not cause acute improvement in 20-m sprint performance in preadolescent boys, as both protocols cause greater fatigue than a typical warm-up. Therefore, their addition to warm-up of preadolescent boys is not recommended.