The strength training program will consist of applying resistance and progressive exercises for strength gain and will be based on the training principles recommended by the American College of Sport Medicine. The exercises were chosen based on a pilot study that successfully applied the protocol to 10 participants with FPD (data to be published) and other strength training studies (MASCALL et al, 2003; DISTEFANO et al, 2009; REIMAN et al, 2012; BALDON et al, 2014; SILVA et al, 2015).

Initially, the goal will be the development of neuromotor control and resistance (load <50% of the one repetition maximum test [1RM]), and in subsequent weeks the goal will be the development of muscle strength (load> 70% 1RM). In addition, the protocol will initially focus on strengthening the hip and trunk muscles and after four weeks of training, exercises for the knee muscles will be included.

Participants who are allocated to this group will perform the same exercise program performed by the STG, but with the addition of exercises that emphasize power gain. As in the other group, initially, the objective will be the development of neuromotor control and resistance (load <50% of the one repetition maximum test [1RM]). However, in subsequent weeks the goal will be to develop strength (load> 70% 1RM) and muscle power (load between 40-60% 1RM).

The strength training program will consist of applying resistance and progressive exercises for strength gain and will be based on the training principles recommended by the American College of Sport Medicine. The exercises were chosen based on a pilot study that successfully applied the protocol to 10 participants with FPD (data to be published) and other strength training studies (MASCALL et al, 2003; DISTEFANO et al, 2009; REIMAN et al, 2012; BALDON et al, 2014; SILVA et al, 2015).

Initially, the goal will be the development of neuromotor control and resistance (load <50% of the one repetition maximum test [1RM]), and in subsequent weeks the goal will be the development of muscle strength (load> 70% 1RM). In addition, the protocol will initially focus on strengthening the hip and trunk muscles and after four weeks of training, exercises for the knee muscles will be included.

Pain intensity will be assessed using a 100-mm Visual Analog Scale (VAS), with 0 indicating no pain and 10 indicating extremely intense pain. Participants will indicate their usual pain and their worst pain during the last week (CROSSLEY et al, 2004). The VAS scores will be computed by measuring the length of the line, in millimeters, from the left end (without pain) until the mark made by the participant.

The Anterior Knee Pain Scale, a translated and validated Portuguese version (DA CUNHA et al, 2013), will be used to evaluate subjective symptoms, such as anterior knee pain and functional limitations related to PFP. The items assessed in the questionnaire are patellar subluxation, lameness, pain, walking, climbing stairs and remaining seated for prolonged time with knees flexed. It has scores of 0 to 100 points, where 100 means no pain and / or functional limitations and 0 means constant pain and several functional limitations (KUJALA et al, 1993). The Anterior Knee Pain Scale is a reliable and valid instrument to evaluate the function in individuals with PFP (CROSSLEY et al, 2004). The final score will be used for statistical analysis.

The kinesiophobia will be assessed using the translated and validated version of the Tampa Scale for Kinesiophobia questionnaire (SIQUEIRA et al, 2007), which is composed of 17 items that evaluate fear of movement, injury or recurrence of injury (MILLER, 1991). This questionnaire is a four-point Likert scale, in which the sum of responses can vary from 17 to 68, and scores greater than 37 indicate the presence of kinesiophobia.