## 4 Discussion  
The aim of the present study was to investigate the effect of a short RW program on the performance of young soccer players in fitness tests and on their running performance during the first 15 min of the second half of league matches. The results of the present study seemed to confirm our hypothesis for some of the physical fitness tests but not for running performance in matches. More specifically, the short RW program of three minutes that we applied limited the decrease in body temperature and the performance in the intense power movements such as jumping and sprinting. However, the running performance of young soccer players did not appear to be affected by RW. It is known that one of the main objectives of the warm-up is to increase the body temperature as it is particularly important for the performance of an athlete. More specifically, it has been reported that an increase of 1 \({}^{\circ}\)C in muscles can lead to a 2-5% improvement in muscle power [3]. Conversely, each decrease in temperature of 1 \({}^{\circ}\)C is accompanied by a decrease in performance of 3% [26]. In the present study, a significant decrease in body temperature was observed after passive rest (a 1.6% decrease). Body temperature after applying the RW program decreased by 0.8%. In a recent study [24], researchers observed that after 1 min of cycling to 90% or 3 min of cycling to 30% of VO2 max, performance in the sprint that followed increased. However, this study was carried out on active male adults. Similar positive effects were observed in a study of soccer players who applied 7 min of jogging at half-time [27]. In tests of acceleration (10 m) and speed (30 m), it was found that passive rest had a negative effect on the performance of young soccer players. More specifically, in the 30 m test, the athletes' time increased by 4.8%. Similar performance decline results have been reported in previous studies. In one of the first studies on this subject, a 2.6% yield decrease was observed [2], while in a more recent study, the decrement reached 3% [27]. These differences may be due to the different methodological approaches of the aforementioned studies such as the participants and the tests used. However, both of the above studies were carried out with the participation of adult soccer players who competed in the fourth division of the Danish league and the elite college league, respectively. It should be mentioned that in the present study, in the RW condition, a decrease in performance of 3.7% was observed. This drop is notable despite the fact that no statistical significance was observed. In addition to the partial eta square indicator, we see a large main effect of 15 min rest (\(\eta^{2}\) = 0.583). Regarding the 10 m test, greater differences were observed between the two conditions. More specifically, after passive rest, the performance of soccer players decreased by 5.8%, while after RW, the decrement was only 0.5%. Additionally, regarding the partial eta square indicator, we see a large main effect between the conditions (\(\eta^{2}\) = 0.435). Previous studies using the 10 m test reported a 2.6% decrement [16], while in studies that measured the speed at 10 m during a match, they observed a decrement of up to 6.2% [28]. Speed in soccer is a particularly important performance factor for the players. It has been reported in previous studies that most sprints during a soccer match last 2-4 s [29]. Therefore, if at the beginning of the second half, the soccer players show the differences observed in the present study for the 10 m sprint test (P (15 min): 1.95 s, decrement 5.8%; 3 min RW: 1.85 s, decrement 0.5%), this means that in a sprint of 2 to 4 s, the soccer player who would have applied RW would travel from 10.8 m to 21.62 m, while the one who would have applied passive rest would travel from 10.25 m to 20.5 m. As we understand, these differences from 0.55 m to 1.12 m can be very important to the outcome of the match.