Dynamic balance improvement in children with Autism Spectrum Disorder after an extracurricular Service-Learning Physical Education program

ABSTRACT This study aimed to examine the acute changes in dynamic balance Postural Control experienced by children with Autism Spectrum Disorder (ASD) who undertook a 6-month extracurricular Service-Learning Physical Education (PE) program. The study used a quasi-experimental design with 23 participants divided into an experimental group and a control group. Limits of Stability protocol was used to measure the children’s postural control. The results showed that the experimental group achieved statistically significant improvements. To conclude, this study provides substantial input about how extracurricular PE activities aimed at developing the general motor proficiency of ASD children can improve their dynamic balance.


Introduction
Autism Spectrum Disorder (ASD) refers to a range of multisystem neurodevelopmental disorders that affect people from early childhood. The prevalence of individuals with ASD has increased substantially in recent decades. 1 In fact, it seems to affect up to 2,5% of the population. 2 Among other issues, regarding social skills, individuals with ASD show a reduced capacity to interact and communicate and they usually present restricted interests and stereotypical and repetitive behaviors. 1,[3][4][5] In addition, they present some difficulties at a motor level. 6 For instance, they display low levels of motor coordination, 7 difficulty selfmonitoring 8 and reduced Postural Control (PC) in bipedal stance when compared to Typically Developing (TD) individuals. 9 PC is a fundamental skill required to maintain postural orientation and equilibrium. It has an important role in an individual's adaptation to changing environmental demands, as well as in the performance of motor skills 10,11 ; it is therefore an important skill to ensure quality of balance for all types of populations. However, children with ASD commonly report PC deficits. 12 In fact, anomalous postural development is one of the earliest observable disruptions in ASD children 13,14 and these deficits persist throughout their development. 6,10,15,16 Thus, it is important to promote PC development among ASD populations from an early age because it is an essential factor affecting prevention of the risk of falls, among other aspects.

Physical Activity and Children with Autism Spectrum Disorder
Physical activity (PA) provides an opportunity for ASD children to increase not only social skills 17,18 but also motor skills. 5,19 Unfortunately, this population usually has fewer possibilities to be involved in extracurricular activities or programs aimed at promoting PA. 4,20,21 Therefore, this lack of participation in sport and exercise may further impact their early childhood development in general, 5 including having reduced opportunities to develop their PC and balance skills. In this regard, this population should be provided with sufficient opportunities to exercise. Nevertheless, effective interventions are required for the promotion of physical education (PE) in children, particularly in the case of ASD individuals because of their characteristics.
Several studies have examined the impact of specific intervention programs for ASD children that focus on promoting PA. For example, a recent meta-analysis concluded that a number of positive effects can be perceived for children with ASD who were exposed to sport programs or PA interventions. 22 The effects of such proposals include an improvement of both motor and social skills. [22][23][24] Thus, participation in sports and exercise programs may have a positive impact on ASD individuals' quality of life. 4 Some of the literature has previously examined PC outcomes of ASD children after a PA program. For example,,25,and 26carried out martial arts programs to uncover their effects on static and dynamic balance, and,27prepared a special six-week-long balance training for ASD children. But to our knowledge, only one study has analyzed the effects on balance of a sports intervention that approached PE in a holistic way, specifically the SPARK program. 28 This 3-month long program obtained positive results in static and dynamic balance; however, it was managed by a number of specialized and expert staff, and carried out in a specific context. In other countries, such as Spain, ASD children do not have this type of programs at their disposal 29,30 ; therefore, there is a need to find innovative ways to provide them with such opportunities, such as the program analyzed in this study.

Physical Activity Promotion through Service-Learning Programs
PA interventions can vary widely depending on their typology. The intervention program whose effects were analyzed in this study was implemented as a Service-Learning (SL) initiative carried out as part of a Physical Education Teacher Training (PETT) program. SL is defined as a teaching methodology that seeks to develop academic and professional skills in the students involved. In PETT programs, SL involves physical interaction and active participation of both the PETT students and the people receiving the service, in this case children with ASD. 31,32 SL initiatives have been found to be very useful for promoting PA and PE in a range of children with developmental disorders. [33][34][35][36] On the one hand, it seeks to develop the academic and professional skills of the students providing the service. On the other hand, it helps to meet a community need; in this case, providing ASD children with opportunities to engage in PA and encourage their social interaction. Hence, sufficiently prepared students can lead SL programs aimed at promoting PE among ASD children. 37 SL literature calls for research examining the effects that this pedagogical model may have on the community. 33,38 Although different studies show that SL programs in the field of PE may be instrumental to promote PA among children with developmental disorders, there are no studies focusing specifically on its effects on PC. Therefore, this article aspires to fill this gap, focusing specifically on children with ASD. This is relevant because this population usually presents an affection on PC and they have reduced opportunities to develop PC and balance skills. Therefore, it seems reasonable to examine whether a PE program through SL may have an impact on the PC of children with ASD.
Therefore, the aim of this study was to examine the acute changes in dynamic balance PC experienced by children with ASD who undertook a 6-month PE program through SL in Spain and to compare them with ASD children who did not participate in such a program. In this way, we will be able to determine whether a SL program is effective as previous specialized programs have demonstrated before in other contexts.

Hypotheses
(1) The experimental group will display a significant improvement in their dynamic balance PC after participating in the SL program.
(2) There will be significant differences in the pretest and posttest measures of dynamic balance PC in favor of the experimental group.

Study Desig N and Participants
This study used a quasi-experimental design of two nonequivalent groups (experimental and control), with pretest and posttest measures, in order to compare how participation in the intervention program affected the participating ASD children. This is a classic design that is used to explore the causal relationship (effect) of the independent variable (PE program) on the dependent variable (dynamic balance) . 39 A total of 34 children with ASD were recruited within a 100 km radius of the University where the research was conducted in Castellón (Spain). The inclusion criteria consisted of: (1) a clinical diagnosis (made by trained professionals) based on the diagnostic standards for ASD established in the DSM-IV-TR or DSM-V-TR, (2) age between 5 and 16 years, (3) absence of any diagnosed illnesses that hindered their performance of PA, (4) IQ ≥ 70, and (5) ability to follow instructions. Of the 34 ASD children initially recruited, 29 met the criteria and were divided into the experimental group (ASD E ) and the control group (ASD C ). The exclusion criteria was based on the non-accomplishment of: (1) clinical diagnosis (made by trained professionals based on the DSM-IV-TR or DSM-V-TR), (2) children younger than 4 or older than 16 years old, (3) presence of any diagnosed illness that hindered their performance of PA. Ultimately, 6 of the participants did not reach the end of the research. The final sample considered in the study was 15 children in the experimental group (ASD E : n = 11 boys, n = 4 girls; age: 10.43 ± 3 years old; body mass: 41.52 ± 14.65 kg; height: 137.47 ± 13.94 cm) and 8 in the control group (ASD C : n = 7 boys, n = 1 girl; age: 10.13 ± 3.09 years old; body mass: 37.2 ± 16.0 kg; height: 140.13 ± 17.18 cm). Figure 1 shows the flow chart of participants. The samples showed no significant differences (Table 1). These children were previously diagnosed with ASD level I (70.4%), level II (18.5%) and level III (11.1%), according to the DSM-IV-TR 40 or DSM-V-TR, 3 thus being 67.9% fully included in the school classrooms, 46.4% with hyperactivity, and 57.1% with impulsive behaviors. Any of these traits prevented the children's involvement in the PA intervention program .

Instruments
All tests were performed in a quiet room, near the university in which we performed the intervention program. The Basic Balance Master system (NeuroCom, version 9.2. Clackamas, OR, USA). Limits of Stability (LOS) protocol was used to measure the children's dynamic postural stability before and after the intervention program, with six months of difference among the measurements. It consisted of a portable force platform (46 cm x 46 cm x 5 cm) connected to a computer. A software program (NeuroCom Balance Manager®) calculated the Velocity of the Center of Pressure (CoP) at a sampling rate of 100 Hz, based on a simple inverted pendulum approximation using the sampled CoP data and the participants' body height. Specifically, for the dynamic test, we obtained the

Balance Test
The dynamic test consisted of LOS and Rhythmic Weight Shift (RWS). During the LOS test, participants had to reach the maximal distance from the initial point after standing for 8 s, in eight directions: 1) forward, 2) forward-right, 3) right, 4) backward-right, 5) backward, 6) backward-left, 7) left, 8) forward-left. Each test started at an initial point and participants had to reach the specific points once the initialized recording test signal was given. The software verified whether the procedures were performed correctly or had to be repeated if the children had started the test before the 8 s or had moved their foot from the platform. Once this test was completed, the participants performed the RWS test, in which they had to move their center of gravity in the AP and L planes at three velocities (slow, medium and fast). These rhythm indications were provided by the software, displaying a pictogram on the screen.

Program Overview
ASD E participated in an extracurricular PE program which was embedded within a SL Project within a PETT. The program followed some guidelines related to organization and the educational approach of the tasks that had been used in previous SL experiences. 37,41 The sessions were managed by three trained coaches who had at least two years of experience in PE and by one special education teacher with expertise in developmental disorders, in particular children with ASD. Each PE session was also supported by at least 12 PETT students and supervised by an expert psychologist and the university professors involved in SL. Thanks to the SL methodology implemented, the children-to-staff ratio was between three and four, depending on each session and age group. Participants in the control group did not carry out extracurricular activities involving PA. This variable was controlled through previous interviews and subsequent reports from the families.
Regarding the PE program, sessions were one hour long and were carried out twice a week between November and May during the 2018/2019 academic year. The participants' attendance record showed a high degree of adherence to the sessions (91.2%). Each child with ASD received an invitation to take part in the PE sessions with a sibling or a friend, so that they felt more comfortable. Thus, between three and five TD children attended  some of the sessions. The program aimed to promote longlasting and autonomous PA habits among children with ASD, providing them with opportunities for future practice of healthy, recreational and educational PA from a general motor proficiency perspective. Table 2 displays a general overview of the program and the sessions that were developed.

Data Analysis
For the data processing, we first performed a descriptive analysis (M ± SD). After the normality test, we performed the Mann-Whitney test for independent samples to verify the nonsignificant differences of the sample characteristics and all the results of the pre conditions, as well as the post conditions. As most parameters showed a normal distribution, to compare the results before and after the intervention, we used Student's t-test for paired samples for all parameters. For all the comparisons, the level of significance was set at p < .05.

Ethical Considerations
This research was approved by the Ethics Committee of the University Jaume I of Castellón, where the study was carried out. In addition, the participants' families signed written informed consent to participate in the study. To counteract ethical issues, the families of the participating children could decide which group to join (experimental or control). Therefore, they all had the possibility to take part in the SL PE program. All the researchers met the requirements established in the Declaration of Helsinki [.431964) Table 3 shows the improvements in the participants' results after the 6-month SL PE program. We observed that RTs decreased for all directions. The differences were significant in the forward (p < .05) and backward (p < .05) directions. For the other parameters, a tendency was observed. However, the results did not show significant differences.

Rhythmic Weight Shift (RWS)
The RWS results improved in all the conditions for the parameters of AP_DCL and AP_MV (Table 4). In the lateral trials, we observed that participants improved their slow and moderate velocities, therefore showing statistical differences in the Lateral_DCL post conditions between the experimental and control groups (p < .05). Slight improvements were also observed in the Lateral_MV parameter in the slow and moderate velocities.

Discussion
The purpose of this study was to examine the acute changes in dynamic balance PC experienced by ASD children who participated in a 6-month SL PE program. Several interesting findings were observed through the quasi-experimental design used in this research. Firstly, children belonging to the experimental group displayed better results in their dynamic balance PC RT and MV after participating in the SL program. These Table 2. Service-Learning program design.

Physical Education Service-Learning program
Design of the program Adaptations Before the sessions, the team carried out several meeting with the families of the ASD children to gather data regarding their characteristics (i.e., interests, personal features). The design of the sessions was based on this information. Thus, the design was adjusted to provide adequate means of communication (i.e., visual support, clear instructions), setting out specific topics for the sessions to have a motivating background considering children's interests, or adapting the stimuli that might affect their sensorial features, among others.

The role of the families
To anticipate the sessions to the children with ASD, the design of the sessions was previously sent to their families so that they could prepare the children for the tasks at home. Simple and repetitive structure: *5-10 minutes warm-up, *45 minutes devoted to working on motor skills *5 minutes dynamic cooldown to finish the session Each session was composed of both group dynamics (e.g. parachute and traditional games and dancing activities), which were carried out mainly during the warm-up and cool-down parts of the session, and activities in groups of three or four children based on age ranges during the main part of the sessions.
Direct command and task assignment.
Materials and resources Facilities Due to the participants' features, many activities were explained using visual aids (i.e. pictograms, modeling the task to perform, etc.) because they are usually more effective than verbal instructions for ASD children. 42 Other materials included balls of different sizes, rings, mats, ropes, bags, bowling pins, etc.
The sessions were carried out in the sports facilities of the university, since these are safe and adequate for this type of activities. This location was adequate to provide the children with a calm space and to avoid disturbing noises.
improvements were statistically significant for the forward_RT and backward_RT measures (p < .05). Secondly, we found significant differences in favor of the ASD E in the lateral moderate_DCL PC category. These results are encouraging because, in general, ASD children show poor PC due to a visual fixation deficit which could explain proprioceptive disorders with impacts on balance and PC, among other aspects. 44 In this regard, the findings of the present study are consistent with previous literature in the field. Several intervention programs examining balance outcomes on ASD children have been implemented previously. For example, a six-week Tai Chi Chuan training program appears to improve performance in dynamic and static balance tests after the intervention. 25 In a similar study, ASD children experienced improvements in PC following participation in an eight-week taekwondo intervention. 26 However, these two programs focused specifically on martial arts, which are sports that tend to be closely linked to balance. [45][46][47][48] Also, a balance training program efficiently improved PC in ASD children. 27 In contrast, the SL program implemented in the present study followed a holistic approach to PE aimed at developing a range of motor and social skills. Thus, it was not only balancefocused, but it addressed the general motor proficiency of children with ASD. Despite this, according to the results of this study, the program may be effective in terms of PC improvement.
Our results can be compared to those obtained by.28 They carried out a 12-week PE program and their results showed that the balance of ASD children improved significantly. Specifically, they found that there was a significant difference between pretest and posttest measures in dynamic balance.
Our results are not so evident because only certain specific measures presented significant differences, although the majority of the measures showed a tendency to improve. 49,50 Therefore, it seems that non-balance-focused programs might also be useful for developing the dynamic balance of ASD children, including not only programs managed by a specialized team only, but also those carried out through SL and managed by PETT students who were guided by experts. This is relevant because it shows that SL may be effective not only for participant students, but also for the community participating in the program, 33 ASD children in this case.
The findings of the present study can also be compared with similar studies carried out in TD children. For example, a sports-based youth development program carried out for 18 weeks improved the participants' dynamic balance, among other aspects. 51 Similarly, a 12-week conventional PA program showed improvements in dynamic balance for healthy Chilean adolescents, 52 and a 10-week recreational football training program found significant improvements in some outcomes of body balance. 53 However, positive results are not always achieved. In this regard, a short-term resistance training program did not display a significant improvement in static or dynamic balance in the participating adolescents. 54 In addition, a systematic review on the effectiveness of exercise interventions in overweight/obese children showed that the results for balance were equivocal. 55 Therefore, it seems that results for balance development in TD children are uncertain, whereas programs for ASD children tend to achieve results that indicate a general improvement. This might suggest that, since ASD children show poor PC, this type of population may be more likely to improve their balance skills after a PE intervention.  Therefore, the more opportunities they have to engage in PA programs, the better; and SL may be an adequate option to provide them with these options while being optimal for university students too. In addition, it is important to highlight that PE programs have been proven to improve motor and social skills [22][23][24] or communication and regulatory skills 56 in individuals with ASD, despite the programs varying in content, outcomes and setting. Therefore, despite not being the focus of the present research, it is worth bearing in mind that the improvement of dynamic balance in this study may not be the only potential advantage for the participating ASD children. 25 The findings of the present study are also relevant because severe peripheral vestibular dysfunction, such as that presented by many ASD children, may have a significant impact on quality of life. 57 In this regard, educational development may also be affected by vestibular dysfunction, 57 and bad postural stabilization may lead to avoidance behavior, lower self-esteem, anxiety (of movement), anger or frustration. 58,59 Therefore, the improvement in PC displayed by participating ASD children may be beneficial to overcome all of these issues. Specific literature has reported that the practice of PA improves the children sensorial system, 27 especially the vestibular one, 60 since they have the opportunity to challenge their gravity. 61 Also, studies as the one by,62 have recommend activities such as the exergames in the context of PA in order to improve the children vestibular PC stability.
These findings lead to the starting point, linked to the importance of providing ASD children with PE opportunities taking into account their specific features in order to induce effective changes in both sensory and motor systems, influencing present and future balance performance. 63 In addition, from a general perspective, targeting motor skills through PE programs could potentially remove barriers to independence and autonomy, since motor difficulties in ASD have been linked to poorer independent-living skills. 64 In fact,,65demonstrated that behavioral, autism-related features and physical conditions were associated with quality of life in individuals with ASD. Therefore, maintaining an active and healthy lifestyle through regular exercise thanks to the SL program may be a key element in improving the present and future quality of life in ASD children. 25 In turn, the literature shows that several SL programs have been carried out to provide ASD populations with PE opportunities. In fact, a recent systematic review on SL through sport reports that most of the groups receiving SL included people with functional diversity or disabilities or children with special educational needs. However, these studies tend to focus on the effects on the students rather than on the recipients of the service, 66 which is what we have addressed here. Therefore, there was a lack of rigorous analysis of the effects of SL on the population receiving the service 31 and our results have tried to contribute to an understanding of this niche.
The findings of this study should be interpreted with caution, since it is subject to some limitations. Firstly, the number of participants was sufficient for the statistical analysis but was too limited to be generalized in a categorical manner. Nevertheless, studies with this type of population usually rely on data gathered with a similar sample size. 67 In addition, the quasi-experimental design of the study attenuates this limitation. The distribution between ASD E and ASD C was not random for two main reasons: on the one hand, to counteract ethical issues related to denying participation in the program, and on the other hand, to ensure the feasibility of the study, since control group participants might not have been able to attend the program for reasons such as incompatibility with the schedule or distance from the activity, among others.
Regardless of these, this study has also some strengths such as the fact that it presented an in-depth, detailed, comprehensive, and objective examination of the variables analyzed. Anyway, future research could replicate this study with wider samples and in different contexts or focus on other specific aspects related to ASD motor skills and quality of life to further examine the possible impact of SL PE programs participation on these outcomes, also in the long term.

Conclusion
In its thorough desire to contribute to a better quality of life for children with ASD, this study analyzed the effectiveness of a 6-month extracurricular SL PE program regarding the development of dynamic balance. On the one hand, ASD E children showed improvements in their dynamic balance PC for the forward_RT, backward_RT, backward_MXE and forward_DCL parameters. On the other hand, they also showed statistically significant improvements in their lateral moderate_DCL PC. It can therefore be concluded that, according to the results obtained, motor skills training based on a holistic and comprehensive PE approach seems to be helpful for reducing PC limitations in terms of dynamic balance. Thus, since this type of programs could be transferred to the daily life of children with ASD in many parts of the world, the outcomes of this study will aid teachers, clinicians and researchers when developing interventions and tests for children with ASD. Finally, a differential trait to highlight in this study lies in the support of the SL methodology when applying the extracurricular PE intervention program. This approach not only enables and facilitates the adequate implementation of the PE sessions, for example in terms of ratio between children with ASD and educational staff, but also helps future PE teachers to acquire inclusive teaching skills in real contexts. 34

Lay Summary
This study shows the improvements in dynamic balance in children with Autism Spectrum Disorder who participated in a Service-Learning Physical Education intervention program of 6 months of duration. These children improved qualitatively their time and maximal excursion point, as well as their capacity to control their direction. For this reason, the children who participated in this program improved their balance, which may prevent their risk of falls and improve their self-confidence when performing motor tasks and interacting with the environment.