2.1 UDL in intervention with students

^{Taunton, Brian and True (2017)} analyzed through a pre-post test the effects of a motor intervention using UDL on students with and with no disabilities. Sixty-seven children between the ages of three and five took part in the study. The sample consisted of 42% with some type of disability and 58% with no disability. Participants were randomly divided into two groups. The control group did not undergo the intervention, only the pre-post test and was composed of 19 students with disabilities and eight students with no disabilities. The experimental group included 20 students with disabilities and 20 students with no disabilities. For measurements, the Gross Motor Development Test (TGMD-2) was used.

The intervention program developed by Tauton, Brian and True (2017), called SKIP - UDL, was designed based on evidence practice of Physical Education and Motor Education, as well as the three universal principles of UDL. There were six weeks of intervention during Physical Education classes, which had external observers to ensure that the teacher was applying the UDL-based motor intervention. At the end, intra-observer agreement was performed which corresponded to 95%. The statistically analyzed results showed differences in motor skill acquisition between the participants of the experimental group and the control group. However, when the groups with disabilities and non-disabilities were analyzed, participants with no disabilities had superior performance in the proposed tests. The authors concluded that, in addition to the intervention improving students' overall motor skills, planning an intervention in Physical Education based on the principles of UDL favors the participation and engagement of students in the proposed activities.

^{Loman, Strickland-Cohen, & Walker (2018)} also used an experimental model (multiple baseline single subject design) to assess the effects of adapted lesson plans and inappropriate behaviors of students with severe disabilities in the school context. The inadequate behaviors of the three students analyzed decreased with the insertion of the UDL principles in the lesson plans and school daily life.

Both studies allocated in this category worked with experimental research methods. The experimental model has been widely used in the national literature for research applied in the SEST (^{Lima & Almeida, 2008}; ^{Lopes-Herrera & Almeida, 2008}; ^{Oliveira, 2016}), because it is possible, through the chosen designs, to determine the causal relationship. effect between two variables. This fact shows the researchers' caution in really identifying the effectiveness of the UDL intervention, whether in motor skills or in the school's daily activities.

The use of UDL for learning, thinking about motor skills, such as the study developed by Tauton, ^{Brian and True (2017)}, raises a discussion about the use of UDL not only for more theoretical subjects in the school context, but also in the area of Physical Education. Promoting a quality motor education supports the student to benefit in several aspects, including: independence and autonomy in performing daily tasks (^{Pereira & Moreira, 2013}).

In this sense, it is important to highlight that, if UDL is still a new concept in our country, in the area of Physical Education it is practically unknown. In an initial research proposed by the authors of this paper, we sought to investigate, through a systematic literature review, the relationship between UDL and Physical Education, but the material found was insufficient to be discussed. The recent study published by van ^{Munster, Lieberman and Grenier (2019)} aimed, through a case study, to describe the different approaches teachers use to include students with disabilities in a New York Elementary School. Thematic analysis identified three main approaches: (a) standardized instruction; (b) differentiated instruction; and (c) instruction based on UDL principles. The authors conclude that by using the differentiated strategy when necessary (one tailored specifically for a student) and the UDL-based strategies in line with the goals of Physical Education, the teacher will favor the participation of all students during the activity.

Although the compiled material is still small, even in the international literature where UDL has been studied for 20 years, it is clear that research applied to students based on UDL principles has shown advances in behavior modification and also in the inclusion of students with disabilities in the regular school.

2.2 UDL in teacher training

^{Mcghie-Richmond and Sung (2013)} offered a UDL course for two groups of teachers: in-service teachers and pre-service teachers (undergraduate students). The course consisted of planning the classes according to UDL principles. A step-by-step guide of this planning was offered to all teachers. For analysis, the authors examined teachers' lesson plans before and after the course. All teachers participating in the training presented modifications to their original lesson plans. Modifications made to the lesson plans following the principles of UDL favored that all students participate and enjoy the learning. Planning was the main object of study of the authors. In this sense, ^{Orsati (2013)} points out that planning is the starting point for the elaboration of inclusive classes.

The research carried out by ^{Navarro et al. (2016)} presented the implementation and evaluation of a teaching professional development program. The study included 47 teachers who attended classroom and online classes on the theme of UDL. As a result, the program evaluation has shown that training has enabled teachers to broaden their competencies in planning and designing inclusive learning experiences for their students.

Teacher education in the perspective of inclusion is discussed both internationally and nationally, highlighting the importance of developing programs for professional training. To ^{Navarro et al. (2016)}, "teachers need to be equipped with appropriate competencies for addressing the diverse needs and preferences of their students and providing them with equal educational opportunities" (p. 25). Regarding the UDL perspective, three key points for reflection stand out: planning (^{Orsati, 2013}), instruction and/or strategies and evaluation (^{Chtena, 2016}).

To ^{Chtena (2016)}, some strategies should be adopted when thinking about structured teaching according to UDL, namely: the use of technology, expository teaching, other classroom activities, assessment and additional support. Such strategies are found in the literature and seek to make the class accessible to everyone. Teacher training programs, in turn, should help to give teachers access to this literature and also to pedagogical practice.

In this scenario, UDL appears as a proposal to enable teachers to practice inclusive practice, because "the greater the possibilities of presenting new knowledge, the greater the possibilities of learning it" (^{Zerbato, 2018}, p. 58). Such a precept is part of the second principle of UDL - that of representation. ^{Rose and Meyer (2002)} point out that this is the principle by which teachers identify most, and attribute this by saying that the basis of representation is the act of teaching.

The curriculum issue is another point that deserves attention when addressing the training of teachers to use the principles of UDL in their classes. To ^{Alves, Ribeiro and Simões (2013)}, UDL allows to offer multiple means for all students to have access to curriculum content. Therefore, it is corroborated with ^{Pletsch, Souza and Orleans (2017)} in discussing that curricular differentiation should not happen through content impoverishment, but rather in reviewing the strategies and technologies that can be used to make the curriculum accessible to all students.

In Brazil, teacher education from a UDL perspective has gained visibility recently. ^{Zerbato (2018)} developed a teacher education program directing UDL to school inclusion. To reflect the pedagogical praxis, the author proposes a model of collaborative formation, in which there is dialogue between theory and practice. Among the research analyzed here, ^{Navarro et al. (2016)} also highlight that the collaboration between several professionals during the teacher training program corroborates a more efficient training.

The literature found and discussed in this category points to the importance of vocational training not only in understanding the concept and principles of UDL, but mainly in the planning and execution of the class, in order to make the activities accessible to all students, implying indirectly in the inclusion of SEST students.

2.3 UDL in the perspective of teaching professionals

In this category, three of the selected papers were grouped. Two of them corresponded to the same author, they are: ^{Katz and Sokal (2016)} and ^{Katz and Sugdan (2013)}. In the 2016 study, the authors used the interview technique to evaluate the effects of a new pedagogy called the "three-block model", which proposes the application of UDL principles from the students' perspective. The sample consisted of 101 students from 51 schools in Canada. Students responded to the interview before the implementation of the new pedagogy and after its implementation. Overall, the analysis showed that students had changes in five categories: learning conceptions, learning processes, interdependence in learning, student self-concept and school involvement. The authors also report that the vast majority of children recognized the changes in the new pedagogy and provided evaluative comments such as "the class has become more united"; "We are not ashamed to position ourselves". Such comments point to an improvement in the socio-emotional climate and also in the instruction design.

^{Katz and Sugdan (2013)} assessed, through field notes, school photographs, and video evidence, the role of school leaders during the UDL implementation process. The results indicated the principal's effort to encourage teachers to participate in the UDL implementation process in the school context. The authors also point out that the success of this implementation is largely due to the participation of this manager for teachers to engage in the proposed initiative.

The study conducted by ^{Lowrey et al. (2017)} examined the stories of seven teachers about the implementation of UDL. All participants shared stories that students with disabilities were included in their teaching plans, as well as the need for more support and training to understand the characteristics, instructional methods, materials, and expression options for incorporating these students into the general curriculum. This meets the need to promote teacher education discussed in the previous category, and dialogues with the studies of formation carried out by ^{Mcghie-Richmond and Sung (2013)} and ^{Navarro et al. (2017)}, analyzed in this systematic review.

It is possible to notice that the three works in this category sought to give voice to the teaching professionals involved in the implementation of the UDL, teachers and managers, as well as the students themselves. Analyzing the implementation of UDL from the perspective of who is inside the school is important to evaluate success points and points to be rethought, since this process is continuous and must be constantly thought and re-thought.

School inclusion is due to several factors, such as public policies, physical structure, school context, intra and interpersonal relationships. In this sense, ^{Tavares, Santos and Freitas (2016)} conducted a research that aimed to investigate whether, from the teachers' point of view, the training received by them contributed to their actions with children with disabilities in regular schools. To this end, the researchers interviewed 52 teachers and applied content analysis to the transcribed interviews. The study data showed that teachers are very frustrated and distressed because they do not feel prepared to work with SEST.

The so-called "fear of the unknown" was also listed by ^{Fiorini (2011)} as a hindrance to school inclusion. Thus, ^{Faria and Camargo (2018)} argue that, in addition to aspects of vocational training, it is important to study how these feelings permeate the teacher's practice, thus indirectly impacting inclusion. Due to that, works that seek to listen to school actors and their perceptions (such as the studies listed in this category) are extremely relevant to understand the process of inclusion in the educational context.

The perspective of the professionals involved in the school universe also corroborates the reflection of teaching practice and the dialogue between theory and practice, which is intrinsically linked to teacher education. In this sense, ^{Lüdke (2012)} states that "we have already gone a long way in the study of the so-called teaching knowledge, to be aware that they are built from different sources, including that linked to the teacher's own experience" (p. 32).

The teacher's experience is also valued by ^{Cruz (2011)} in stating that "we believe that theory provides guidance and reading tools, but we also assume [that] the meanings people take with them are linked to their experiences" (p. 27). This interlocution of knowledge (theory and practice) also occurs when we think about teaching and the contributions that research can make to the school environment.