Preheating in the Improvement of Knee Stability and Quadriceps Strength in Rugby Players

• Warmup (Other), also known as Experimental group: The intervention through exercises will consist in the application of the protocol described by Waldén et al. The objective of the application of this exercise protocol is to produce an improvement in the stability of the knee and the strength of the quadriceps. Before carrying out the exercises, a continuous race will be carried out for 5 minutes, once this first step is finished we will proceed to the realization of the exercises that will be, squats with both legs placing the hands on the hips, feet placed at the width of the shoulders, lowering with a straight back and without raising the heels of the floor, 3 series of 15 repetitions, squats on one leg with the hands on the hips and leg not supported extended forward, 3 sets of 10 repetitions with each leg and jump forward with one leg with the hands on the hips and jump back to return to the starting position, 3 sets of 10 repetitions with each leg

Primary outcomes

• Change from baseline knee stability after treatment and at month [Screening visit, within the first seven days after treatment and after one month follow-up visit]: It will be done using the Y-Balance test. The barefoot sportswoman will be placed with the toes in the center of the Y marked on the floor with adhesive tape. Each of them will have six trials with each foot in each direction (anterior, posterolateral and posteromedial). Subsequently, they will have three attempts with each leg in each direction, taking the best mark of each leg in each direction. The athlete must return to the initial position without losing balance, because if she does not succeed, that attempt will be void. The distance to be measured includes from the central mark where we place the toes to the point where the patient supports the tip of the toes. The unit of measure of this measuring instrument is the centimeter. A higher score indicates greater knee stability.

Secondary outcomes

• Change from baseline quadriceps strength after treatment and at month [Screening visit, within the first seven days after treatment and after one month follow-up visit]: It will be done by applying the Single leg hop test. With this test, the quadriceps strength will be measured. With the patient in monopodal and barefoot support, and with the toes placed on a mark made on the floor with adhesive tape, he will make a leap forward, maintaining the balance at least one second. Each player will perform 6 warm-up jumps with each leg. Subsequently you will have three attempts with each leg and the greatest distance achieved with each one will be taken. The distance will be measured from the initial mark, to where the subject's heel lands, with cm being the unit of measure for the test. A greater distance indicates a greater force of quadriceps.

Sex: Female, ages: 18 Years to 30 Years, accepts healthy volunteers

Inclusion Criteria:

* Female rugby players
* With an age range of 18 to 30 years
* That participate in the Valencian territorial category 1
* Without diagnosis of lower limb injury at the time of starting the study

Exclusion Criteria:

* Players who suffer an injury or illness that prevents them from performing the protocol
* Are performing another specific physiotherapy program of knee stability and quadriceps strength
* Who had undergone the anterior cruciate ligament less than a year ago
* Have not signed the informed consent.