En aquest estudi es pretén fer una anàlisi descriptiva a través d’una investigació experimental dels efectes d’un entrenament excèntric de vuit setmanes mitjançant el Nordic Hamstring exercise (NHE) en la millora de la força i la velocitat. Per a la seva realització, es van fer unes proves inicials, seguides del protocol de NHE, per posteriorment repetir les proves. La mostra és de 22 jugadores de futbol en categoria cadet-juvenil i es dividiran en dos grups: el grup experimental (n=11) el qual se li afegirà el protocol de NHE a l’entrenament ordinari, i el grup control (n=11) les quals només realitzaran el pre i post test. Els resultats seran obtinguts a través d’una comparació intragrup i la diferència entre ambdós tests determinarà la possible millora. Altres variables que també es tenen en compte són la posició al terreny de joc i l’any de naixement. Com a conclusió general, podem afirmar que el protocol de NHE ha provocat una millora de la velocitat i la força en les jugadores del grup experimental respecte al grup control.

The aim of this research project is to make a descriptive analysis through a practical investigation on the effects of an excentric training on the improvement of strength and speed. This training involves the Nordic Hamstring Exercise (NHE) and lasts 8 weeks. In order to develop this investigation, some preliminary tests are performed, followed by the NHE protocol, and lastly the initial tests are repeated some time later. The data for this study includes 22 football players in the cadet juvenile category. The girls are divided in two different groups: the experimental group (n=11), to which the protocol was added during their football practice, and the control group (n=11) which only involved the pre and post test. The results will be obtained through an intragroup comparison and the difference between both tests will determine the possible improvement. Some other variables to keep in mind are the players’ position and the date of birth. As a general conclusion, we can confirm that the NHE protocol has created an improvement on their speed and strength in the players from the experimental group compared to the ones from the control group.