How Schroth Therapists Vary the Implementation of Schroth Worldwide for Adolescents with Idiopathic Scoliosis: A Mixed Methods Study

(1) Background: Schroth is a type of physiotherapeutic scoliosis specific exercise (PSSE) prescribed to adolescents with idiopathic scoliosis (AIS). Studies have investigated the effectiveness of Schroth but are yet to elucidate how Schroth is applied clinically and the factors that influence their prescription. (2) Methods: A mixed methods design was used comprising an anonymous survey and semi-structured interviews of Schroth therapists who treated AIS and who were publicly listed on the Barcelona Scoliosis Physical Therapy School or the International Schroth 3-dimensional Scoliosis Therapy School websites. The survey included 64 questions covering demographics, session and treatment characteristics, and whether therapists included other treatment modalities in their clinical practice. A convenience sample of survey participants were invited to participate in a semi-structured interview to further explore the factors that influenced their prescription of Schroth for AIS. Results from the survey were analyzed descriptively (n, %), whereas inductive thematic analysis was used for the interviews. (3) Results: of the 173 survey respondents (18% response rate), most were from Europe and North America (64.0%), female (78.6%), physiotherapists (96.0%), and worked in private settings (72.3%). Fifty-two per cent of participants used other types of PSSE as an adjunct to Schroth, the Scientific Exercise Approach to Scoliosis (SEAS) being the most frequently used (37.9%). Non-PSSE methods were used ‘at some point’ as an adjunct by 98.8% of participants, including massage and other soft tissue techniques (80.9%), Pilates (46.6%), and Yoga (31.5%). The Schroth techniques used by all survey respondents included breathing and pelvic corrections. Seven participants were interviewed, but data saturation was achieved after only four interviews. Thematic analysis revealed four, inter-related broad themes describing the factors that influenced Schroth prescription for AIS: (1) the adolescent as a whole, including physical, emotional and mental characteristics, and patient goals, (2) family, including parent relationship with the adolescent and the motivation of parents in regard to Schroth, (3) the systems within which the treatment was being offered, such as vicinity to the clinic and the presence of financial insurance support, and (4) therapist characteristics, such as their training and experience. (4) Conclusions: Schroth therapists worldwide use a variety of adjunctive methods to treat AIS. Therapists prescribing Schroth exercises to AIS consider the complex interplay of intra-, inter- and extra-personal factors in clinical practice. These considerations move beyond the three components of evidence-based practice of research, patient preferences, and clinical expertise, towards a systems-based reflection on exercise prescription.


Introduction
Idiopathic scoliosis is diagnosed when all other causes of scoliosis have been excluded [1].Adolescent idiopathic Scoliosis (AIS) affects 2% to 3% of the population, of which only 0.3% to 0.5% of affected patients will have a curvature of >20 degrees, the curve magnitude at which treatment is generally recommended [1,2].AIS is diagnosed from 10 to 17 years of age [2] and progression risk is most heightened at the beginning of puberty [2][3][4].Years ago, research confirmed that vertebral growth is modulated by loading, as described by the Heuter-Volkmann principle [5].The need for more research was suggested to quantify this relationship to permit a better design of conservative treatment of spinal deformity during the adolescent growth spurt [5].Conservative treatment for AIS may include regular clinical evaluation, physiotherapeutic scoliosis specific exercises (PSSE) and bracing, before surgery is recommended for larger curves [2].The term PSSE was introduced and defined by the International Society of Scoliosis and Orthopedic and Rehabilitation Treatment (SOSORT) to include the following: (1) autocorrection in three dimensions, (2) stabilization of the corrected posture, (3) integration into activities of daily living, and (4) patient education [2].Multiple PSSE training schools claim to alter the asymmetric loading [5][6][7] that occurs with AIS.The aim is to promote spinal and trunk alignment using specific exercises to reduce or stop the asymmetric loading and potentially stopping scoliosis progression [7].
PSSE is taught to therapists around the world using methods from various teaching schools [7].The specific characteristics of each PSSE program and the factors influencing programming decisions taught by varying schools are not always explicit in the literature [8], which may create challenges for the application of the methods in clinical practice and research studies [9].When details are provided within the literature, specifics about exercise dosage, such as frequency and duration, differ considerably between studies [10].No study has described how therapists trained in PSSE worldwide are applying therapy to patients with AIS.Furthermore, no studies that investigate the benefit of PSSE for AIS have justified the PSSE prescription in relation to the extent of the present spinal and postural deformity in the AIS treatment groups.This may go some way to explaining why only 21% of respondents to a survey of Scoliosis Research Society members prescribe or refer for PSSE for AIS [11].
Schroth, a type of PSSE, is a complex exercise treatment, taught by multiple therapists across multiple continents.Understanding how Schroth is being applied to AIS worldwide once therapists have completed training and the key factors that influence the success of exercise treatment for AIS, has not been elucidated to date [8].The Schroth method is one of the most frequently studied and used PSSE methods to date [12].However, studies have generally focused on comparisons of the treatment against other conservative treatments rather than exploring the impact that a variation in Schroth prescription (e.g., exercise, intensity, repetitions) has for various amounts of curve deformity.Therefore, to increase the understanding of how Schroth is applied into current clinical practice, this study aimed to explore how therapists are applying the Schroth method for AIS, and the factors that influence their prescription in clinical practice worldwide.To do this, the survey aimed to explore the following research questions: (1) Is the application of Schroth consistent across trained therapists treating AIS? and (2) Do therapists combine Schroth exercises with other treatment methods to treat AIS?The results of the survey were then used by the researchers to help formulate open-ended interview questions to explore the following: (1) What are the factors that influence prescription of Schroth for AIS worldwide?and (2) What is the rationale for the treatment programming and application?Together, the results of these two parts of the study were used to answer the question 'How Schroth therapists vary the implementation of Schroth worldwide for adolescents with idiopathic scoliosis' in the form of a mixed methods study.

Survey
Schroth therapists were invited via email to participate in an anonymous online survey (Appendix C) via REDCap (over twelve weeks).Survey questions were developed using a comprehensive list of Schroth treatment techniques and exercise options listed in course content [17] and a published protocol [18].The survey included 64 questions covering demographics, session characteristics such as duration, treatment characteristics such as session duration, and exercises used in Schroth, along with the inclusion of other PSSE, non-PSSE, and any other exercises that they used within clinical practice.

Interviews
All survey participants were invited to provide their details in an unlinked form via REDCap to receive an invitation to participate in a semi-structured interview.Open-

Data Collection Survey
Schroth therapists were invited via email to participate in an anonymous online survey (Appendix C) via REDCap (over twelve weeks).Survey questions were developed using a comprehensive list of Schroth treatment techniques and exercise options listed in course content [17] and a published protocol [18].The survey included 64 questions covering demographics, session characteristics such as duration, treatment characteristics such as session duration, and exercises used in Schroth, along with the inclusion of other PSSE, non-PSSE, and any other exercises that they used within clinical practice.

Interviews
All survey participants were invited to provide their details in an unlinked form via REDCap to receive an invitation to participate in a semi-structured interview.Open-ended questions (Appendix D) were developed following analysis of survey responses and were based around a basic hypothetical scenario of an adolescent with idiopathic scoliosis, which aimed to elicit the following information: (1) factors that influenced the prescription of Schroth therapy in AIS, and (2) rationale for treatment programming and application.The interviews were conducted, recorded, and transcribed by RM via Zoom.RM is an Australian female physiotherapist with 22 years of experience, who trained and practiced in the BSPTS method for 6 years and is completing a Master of Research in Australia.The transcription was checked by RM and EI and then emailed for respondent validation.EI is a physiotherapist with 6 years of experience and qualitative research experience.

Data Analysis Survey
The survey was analyzed using descriptive statistics in Microsoft Excel for Mac V16.58.The data were grouped into (1) demographics, (2) general characteristics of the program, (3) frequency and duration of treatment, (4) SOSORT, PSSE, and non-PSSE features, (5) cues, corrections, and techniques, (6) strategies to adjust exercise difficulty, (7) support material, (8) factors affecting prescription, and (9) compliance monitoring.Response frequencies were calculated from valid responses with missing responses stated as a percentage of total participants.

Interview
To minimize the risk of bias given that RM is trained and certified in BSPTS, EI, who does not have specific scoliosis or Schroth experience or training, was also involved in the inductive thematic analysis of the interview data.The analysis took an iterative approach, as described by Braun and Clarke (2006), where new codes were independently developed, cross-checked by two members (RM and EI), and once agreement was reached, the codes were grouped into themes to ensure authenticity with the experience of the participants [19].Any disagreements were resolved through discussion with a third investigator (VP).The point of data saturation was monitored during recruitment.Saturation was reached when no new themes emerged from interviews.Interviews to explore the factors that influenced Schroth prescription were conducted between August and October 2021.The social ecological model of health was used as the lens to interpret and triangulate the findings [20].

Characteristics of Schroth Program
A majority (87.3%) of participants reported being 'very' or 'somewhat' familiar with these SOSORT guidelines (Table 2).Most participants reported using the recommended components of PSSE according to SOSORT guidelines [2], with 5% 'rarely' or 'never' following these recommendations (Table 3).Other types of PSSE as an adjunct to Schroth were used by 52.5% of participants, SEAS being the most popular (Figure 2).Non-PSSE methods were used 'at some point' as an adjunct by 98.8% of participants, where massage and other soft tissue techniques were the most popular (80.9%) followed by Pilates (46.6%) and Yoga (31.5%) (Figure 2).Other types of PSSE as an adjunct to Schroth were used by 52.5% of participants, SEAS being the most popular (Figure 2).Non-PSSE methods were used 'at some point' as an adjunct by 98.8% of participants, where massage and other soft tissue techniques were the most popular (80.9%) followed by Pilates (46.6%) and Yoga (31.5%) (Figure 2).
Most participants conducted more than five sessions per week (74.5%) with a majority (77.8%) using Schroth for AIS for five or more hours per week (Table 3).The majority of sessions lasted 60 min per session (60.8%) (Table 3).Most (94.2%) recommended sport participation, and all (100.0%)provided a home exercise program, although the frequency of recommendation did vary (Table 2).

Factors Affecting Exercise Prescription
Participants reported that exercise prescription was 'always' or 'often' or 'sometimes' (97.1%) determined by the location of the curve (Figure 5) and the presence of more than one curve (100.0%)(Figure 5).Attendance at the clinic was also perceived by participants to be affected by the motivation of the parents (94.9%) and the adolescent (96.4%) (Figure 5).

Factors Affecting Exercise Prescription
Participants reported that exercise prescription was 'always' or 'often' or 'sometimes' (97.1%) determined by the location of the curve (Figure 5) and the presence of more than one curve (100.0%)(Figure 5).Attendance at the clinic was also perceived by participants to be affected by the motivation of the parents (94.9%) and the adolescent (96.4%) (Figure 5).
Participants 'always' or 'often' provided education and support to AIS using photos/diagrams (86.8%) (Figure 6) and monitored compliance using a logbook (39.4%) (Figure 7).Performance checklists were only used by a minority (34.6%) of participants and most (76.1%) had designed the checklist themselves (Table 3).

Factors Affecting Exercise Prescription
Participants reported that exercise prescription was 'always' or 'often' or 'sometimes' (97.1%) determined by the location of the curve (Figure 5) and the presence of more than one curve (100.0%)(Figure 5).Attendance at the clinic was also perceived by participants to be affected by the motivation of the parents (94.9%) and the adolescent (96.4%) (Figure 5).
Participants 'always' or 'often' provided education and support to AIS using photos/diagrams (86.8%) (Figure 6) and monitored compliance using a logbook (39.4%) (Figure 7).Performance checklists were only used by a minority (34.6%) of participants and most (76.1%) had designed the checklist themselves (Table 3).Participants 'always' or 'often' provided education and support to AIS using photos/diagrams (86.8%) (Figure 6) and monitored compliance using a logbook (39.4%) (Figure 7).Performance checklists were only used by a minority (34.6%) of participants and most (76.1%) had designed the checklist themselves (Table 3).

Interview Participant Demographics
The interview participants were from Europe (n = 3), North America (n = 2), and South America (n = 2).Two had BSPTS-only training, one had ISST-only training, and four had both.Two were previous colleagues of RM but had no prior involvement in the project.EI did not know any participants.All participants had between two and nine years of Schroth experience treating AIS.

Thematic Analysis
Data saturation occurred by the fourth interview; however, three more interviews were conducted to confirm saturation and ensure we achieved representativeness of geographical spread and clinical experience.
Throughout coding, any distinct differences between participants from different regions were considered; however, no specific geographic influences beyond the major underlying themes were noted.Consequently, we decided not to group participants according to location during thematic analysis.Four super-ordinate themes emerged through

Interview Participant Demographics
The interview participants were from Europe (n = 3), North America (n = 2), and South America (n = 2).Two had BSPTS-only training, one had ISST-only training, and four had both.Two were previous colleagues of RM but had no prior involvement in the project.EI did not know any participants.All participants had between two and nine years of Schroth experience treating AIS.

Thematic Analysis
Data saturation occurred by the fourth interview; however, three more interviews were conducted to confirm saturation and ensure we achieved representativeness of geographical spread and clinical experience.
Throughout coding, any distinct differences between participants from different regions were considered; however, no specific geographic influences beyond the major underlying themes were noted.Consequently, we decided not to group participants according to location during thematic analysis.Four super-ordinate themes emerged through

Interview Participant Demographics
The interview participants were from Europe (n = 3), North America (n = 2), and South America (n = 2).Two had BSPTS-only training, one had ISST-only training, and four had both.Two were previous colleagues of RM but had no prior involvement in the project.EI did not know any participants.All participants had between two and nine years of Schroth experience treating AIS.

Thematic Analysis
Data saturation occurred by the fourth interview; however, three more interviews were conducted to confirm saturation and ensure we achieved representativeness of geographical spread and clinical experience.
Throughout coding, any distinct differences between participants from different regions were considered; however, no specific geographic influences beyond the major underlying themes were noted.Consequently, we decided not to group participants according to location during thematic analysis.Four super-ordinate themes emerged through thematic analysis: (1) adolescent as a whole; (2) family; (3) systems, and (4) therapist (Table 4).Table 4. Themes, subthemes, and selected survey quotations from study interviews.
Theme 1: Adolescent as a whole Participants described various characteristics of the adolescent that influenced prescription including how there are multiple emotional and physical factors within the adolescent when prescribing Schroth and how the patient preferences were also an important factor that determined the Schroth program.
Participants believed that emotional maturity helped with coping with diagnosis and therapy.
" [It] depends on the adolescent's comprehension and capacity to do their correction, the breathing. . ..it's not always connected with the age. ..it's connected more with the maturity, cognitive maturity."(P5, female, South America, BSPTS, 8 years experience) Participants talked about the adolescent's preferences influencing prescription, for example, sport.". ..I'll actually have [the dancers] show me their dance moves.We break it down and then we talk about how much they're going to hold their more neutral curve and be able to perform those activities as safely as possible. ..I work on stuff that's more important to them."(P4, female, North America, BSPTS, 5 years experience) The physical characteristics and physical capacity of the adolescents "I usually start from the floor....so it's prone, supine and side-lying because I use gravity first to help them...afterwards when they are good in this exercise in these positions and they   Highly supportive parents assisted with more intense programs.
"Sometimes there are mothers who just want to have more.'What can we do?'" (P7, male, Europe, ISST and BSPTS, 7 years' experience) Theme 3: Systems Participants described how systems influenced Schroth prescription.The cost of treatment and the availability of funding influenced the frequency of sessions, and therefore, exercise prescription.Medical hierarchy was also a factor with doctor support, or lack thereof, positively and negatively affecting attendance at the clinic and referrals for X-ray assessment.
External factors influenced prescription, especially attendance.
"I do think most people choose half-an-hour because of the benefits.Their funding through their insurance company probably covers a certain amount per visit, and so I think most people do opt for the shorter [sessions].I have had some patients come twice a week, but very rarely.I think most don't have the funding for that, and some have no funding so some may just come in every three weeks for half-an-hour."(P1, female, North America, ISST and BSPTS, 3 years' experience) Cost of treatment, and availability of insurance, affected attendance.Each theme interacted dynamically with each other, as depicted diagrammatically in Figure 8. Namely, factors that influence Schroth prescription are shaped by parents (the boat) and the adolescent (the child in the boat), who is empowered by the therapist (paddle) to achieve their goals within the specific health systems and contexts (waterway) of the therapy.

Discussion
Our study found that the application of Schroth in AIS in the clinic is highly variable.The journey may often be arduous which means that the factors affecting Schroth prescription can change over time.The lack of clarity of how Schroth therapy is applied for AIS may be a possible reason for the lack of confidence of Scoliosis Research Society (SRS) members in referring for PSSE for AIS [11].Furthermore, Schroth therapists use multiple treatment methods beyond BSPTS and ISST methods to treat AIS [17,18].Treatments applied by Schroth therapists included core components of Schroth, including a variety of cues (e.g., tactile, verbal), corrections (e.g., pelvic corrections, axial expansions), and tools (e.g., various props, mirrors) to deliver and adjust the program [17].The use of these core components was consistent.However, adaptations were made to suit the patients and context [17,18] and included the use of more peripheral aspects of the treatment, and less often, other PSSE, such as SEAS, and non-PSSE, such as strength training, flexibility, and massage.These reports of large variations in approach by the Schroth therapists in this study are not replicated in the current research studies, with multiple studies focusing simply on exploring the benefits of one approach using Schroth compared with other treatments or no treatment [12,18,21,22].There is also a lack of description in these studies regarding how the Schroth therapy prescription may vary according to the level of structural deformity in AIS.
In our study, Schroth therapists indicated that intensity is adjusted in multiple ways including a change in repetitions, duration, and adding or removing of props.This variation in the application of Schroth is not well explained in published randomized controlled trials, which can make application into clinical practice difficult [9].Other factors that add to the complexity of the treatments being applied were the recommendations to participate in sport and integrating treatment into activities of daily living (Figure 2).Both

Discussion
Our study found that the application of Schroth in AIS in the clinic is highly variable.The journey may often be arduous which means that the factors affecting Schroth prescription can change over time.The lack of clarity of how Schroth therapy is applied for AIS may be a possible reason for the lack of confidence of Scoliosis Research Society (SRS) members in referring for PSSE for AIS [11].Furthermore, Schroth therapists use multiple treatment methods beyond BSPTS and ISST methods to treat AIS [17,18].Treatments applied by Schroth therapists included core components of Schroth, including a variety of cues (e.g., tactile, verbal), corrections (e.g., pelvic corrections, axial expansions), and tools (e.g., various props, mirrors) to deliver and adjust the program [17].The use of these core components was consistent.However, adaptations were made to suit the patients and context [17,18] and included the use of more peripheral aspects of the treatment, and less often, other PSSE, such as SEAS, and non-PSSE, such as strength training, flexibility, and massage.These reports of large variations in approach by the Schroth therapists in this study are not replicated in the current research studies, with multiple studies focusing simply on exploring the benefits of one approach using Schroth compared with other treatments or no treatment [12,18,21,22].There is also a lack of description in these studies regarding how the Schroth therapy prescription may vary according to the level of structural deformity in AIS.
In our study, Schroth therapists indicated that intensity is adjusted in multiple ways including a change in repetitions, duration, and adding or removing of props.This variation in the application of Schroth is not well explained in published randomized controlled trials, which can make application into clinical practice difficult [9].Other factors that add to the complexity of the treatments being applied were the recommendations to participate in sport and integrating treatment into activities of daily living (Figure 2).Both these recommendations are in accordance with the current SOSORT guidelines [2], but how these recommendations are applied in randomized controlled trials has not always been made clear by researchers [9].
The interviews provided an opportunity to explore the factors influencing Schroth prescription in AIS, with four themes identified that interact and influence prescription: (1) the adolescent, (2) the adolescent-parent relationship, (3) the systems, and (4) the therapist, in which Schroth therapy takes place.These themes appear to fit well into the social ecological model of health, with consideration of treatment influencing factors related to the patient and the systems and people (parents and therapist) in their treatment network [20].
The participants described how the experience of the therapist, combined with the characteristics of the child and support from the parents were major influences in the Schroth program.One of the factors influencing attendance at the clinic was affordability and ease of access.Without a good support system from doctors, financial support, and easy access to a Schroth clinic, the frequency of treatment reduced, or telehealth became more frequent.That is, therapists must adapt their programs to suit the state of the systems around them, raising issues of equity and fairness.It is possible that if the adolescent exists within a complex medical system that is not supportive of Schroth, then this creates a variation in accessibility to Schroth treatment and the frequency of supervised sessions reduces.The supervised sessions appear to be important because the completion of a formal Schroth training program with a Schroth instructor has been shown to correlate with an increase in compliance in a home exercise program [23].It would be useful to determine the level of supervision, system support and accessibility, and motivation strategies required to achieve positive outcomes considering the supervision of Schroth exercises has been noted to be more beneficial than unsupervised Schroth [21].Overall, the Schroth therapists are having to adapt their programs to suit the systems and therefore no one program of treatment is likely to be the same as another given the varying health systems across the world.It would therefore be useful for medical doctors considering referring AIS to Schroth therapists to know more about how the prescritpion of Schroth is being adapted to suit the curve type and size.For the 78% of surgeons from the SRS surveyed who do not refer AIS for PSSE, the main reasons cited were a lack of supporting research, that PSSE offers no value, and the lack of access to a facility providing PSSE [11].
Despite the fact Schroth therapists in our study commonly incorporated other PSSE and non-PSSE into their treatment plans for AIS, the current research on Schroth is not representative of a mixed approach utilized by more than half of therapists in this study.Even a recent systematic review investigating the effects of the Schroth method compared with core stabilization exercises, and another comparing Schroth and SEAS, included studies compared interventions but were not looking for the effects of combining methods [24,25].

Research has not confirmed the best types of PSSE or PSSE combinations with and without any non-PSSE adjuncts [8].
Future studies should clarify the effect of combining different corrective exercise modalities as well as the most appropriate dose in terms of number and duration of therapeutic sessions [8].Indeed, future research should explore how combinations of PSSE with and without non-PSSE, as well as other characteristics of the program and level of supervision and compliance, may impact outcomes.
Consideration of the findings will enable future trials to evaluate interventions that are generalizable to the real-world application of Schroth therapy for AIS.For example, the clinical feasibility of interventions worldwide should account for systemic constraints to optimal exercise prescription, including financial barriers and vicinity to a clinic.Future studies could explore the effects of combinations of Schroth with other PSSE and non-PSSE methods for AIS with consideration of the factors influencing prescription described by participants in our study to optimize outcomes for AIS.

Limitations
This study was strengthened by its mixed methods design, which enabled us to further explore the factors influencing exercise prescription in AIS by Schroth therapists [26].Although participants in both stages of this study were generally representative of Schroth therapists worldwide, a limitation was that the study was conducted in English, thereby limiting the participation of individuals who could not communicate in English.This may have contributed to the low response rate (18%) for the survey.The study responses were also limited mostly to women.Finally, while we aimed to achieve purposeful sampling for increased representativeness of interviewees, only a small number of participants provided their contact details to be interviewed.This meant we could only achieve a convenience sample.Nevertheless, we were able to reach data saturation during thematic analysis of the interviews.

Conclusions
This study provides an insight into how Schroth therapists vary the implementation of Schroth worldwide for adolescents with idiopathic scoliosis.Schroth therapists worldwide use a variety of adjunctive methods to treat AIS, including PSSE and non-PSSE methods.The prescription of Schroth is influenced by the adolescent, their parent/s, the therapist, and the systems within which treatment is applied, aligning with a person-and familycentred approach to care.Therapists are more likely to be able to provide more frequent supervised sessions in a supportive health care system, particularly when there is a positive relationship between adolescent and parents.The overall dose and types of exercises prescribed are influenced by the characteristics and motivation of the adolescent and the experience and training of the therapist.Specify the study design in the "Methods" section with a commonly used term (e.g., cross-sectional or longitudinal).3 Data collection methods 5a Describe the questionnaire (e.g., number of sections, number of questions, number and names of instruments used).5 5b Describe all questionnaire instruments that were used in the survey to measure particular concepts.Report target population reported validity and reliability information, scoring/classification procedure, and reference links (if any).

5c
Provide information on pretesting of the questionnaire, if performed (in the article or in an online supplement).Report the method of pretesting, number of times questionnaire was pre-tested, number and demographics of participants used for pretesting, and the level of similarity of demographics between pre-testing participants and sample population.

Not performed 5d
Questionnaire, if possible, should be fully provided (in the article, or as appendices or an online supplement).35

Sample characteristics 6a
Describe the study population (i.e., background, locations, eligibility criteria for participant inclusion in survey, exclusion criteria).

4, 5 6b
Describe the sampling techniques used (e.g., single stage or multistage sampling, simple random sampling, stratified sampling, cluster sampling, convenience sampling).Specify the locations of sample participants whenever clustered sampling was applied.

4, 5 6c
Provide information on sample size, along with details of sample size calculation.

4, 5 6d
Describe how representative the sample is of the study population (or target population if possible), particularly for population-based surveys.23

Survey administration 7a
Provide information on modes of questionnaire administration including the type and number of contacts, the location where the survey was conducted (e.g., outpatient room or by use of online tools, such as Survey Monkey).

4, 5 7b
Provide information of survey's time frame, such as periods of recruitment, exposure, and follow-up days.4 7c Provide information on the entry process: ->For non-web-based surveys, provide approaches to minimize human error in data entry.->For web-based surveys, provide approaches to prevent "multiple participation" of participants.

Not performed
Study preparation 8 Describe any preparation process before conducting the survey (e.g., interviewers' training process, advertising the survey).Not performed

Ethical considerations 9a
Provide information on ethical approval for the survey if obtained, including informed consent, institutional review board [IRB] approval, Helsinki declaration, and good clinical practice [GCP] declaration (as appropriate).

9c
Provide information about survey anonymity and confidentiality and describe what mechanisms were used to protect unauthorized access.5

Statistical analysis 10a
Describe statistical methods and analytical approach.Report the statistical software that was used for data analysis.5 10b Report any modification of variables used in the analysis, along with reference (if available).

No modifications made 10c
Report details about how missing data were handled.Then branch off-if they choose more than one answer in question 3 they will be directed to question 4. If they only choose one answer in question 3 then they will be directed to question 5.

4.
If you are certified in more than one method, choose the statement that is most applicable to you:   Aim: To determine the factors that influence Schroth therapists' decisions when prescribing Schroth therapy to patients.
Questions were refined once the survey results were received and analysed.This updated version of the interview questions was submitted in an amended ethics application and approved.The semi-structured interview was recorded on Zoom (camera on) by RM and took place at a time suitable for the participant.The recording was saved on Macquarie University Office 365 account.The interview was transcribed line by line, checked by RM, EI, and the individual participant, and saved on Macquarie University Office 365 account.
The interviews each took approximately 45 to 60 min.The Interview 'Thank you for participating today, [insert interviewee name].My name is Rosemary Marchese and I will be conducting this interview today.The purpose of the interview is to explore factors influencing your decisions when prescribing Schroth therapy to adolescents with idiopathic scoliosis.You can stop the interview at any time, and you are also encouraged to stop and ask questions or seek further clarification.You will be given a simple case study that we will discuss during the interview.
This interview is being recorded for research purposes.Are you happy to continue?Case study: Imagine this scenario in your clinic.An adolescent child attends with their family and would like to start Schroth therapy for idiopathic scoliosis.
[Note: Details of the case study have been minimised on purpose to maximise the opportunity for the participant to ask questions and for the importance of those questions to be explored by the Interviewer.]Questions: 1.
To determine your exercise prescription for this adolescent, what further information would you want to know before commencing treatment?2.
Why are those factors important to consider?
Example: If the interviewee asks the child's age, then the Interviewer can ask the interviewee to explain why age is important.

1.
Tell me about your typical choice of Schroth exercises in your first week of treatment for this patient.

2.
Tell me about your typical choice of Schroth exercises once the patient is more experienced, say after two or three months of treatment.

3.
Would there be any Schroth exercises that you would prefer or any that you would avoid, for this patient, and why? 4.
Have you ever modified a Schroth exercise from the original training you received, and if so how and why? 5.
Are there any Schroth exercises that you believe are harmful to the patient and why? 6.
Would your own professional experience and personal circumstances influence your treatment of this patient or your Schroth career?How?
What factors influence your decisions in regard to the number of exercises you prescribe for an adolescent with idiopathic scoliosis (AIS)? 2.
Explain the personal factors within the child and their situation that influences your exercise prescription.

3.
If the curve was bigger/smaller what would change in your approach?4.
If the child was younger/older what would change in your approach? 5.
What factors influence your decision in regard to the type of exercises you prescribe for patients with AIS? 6.
Does the adolescent's personal situation, for example, vicinity to the clinic, finances, family support, influence your prescription?If so, how? 7.
Does the adolescent's medical or health situation, for example size of curve, Risser sign, use of a brace, influence your prescription?If so, how?This interview will be transcribed line by line.I will email you the transcription for you to check.You will have a week to respond with any comments that you may have.
Thank you for your time.
Then close the interview.

Figure 1 .
Figure 1.Flowchart of participant inclusion through the study: Part 1, a survey of Schroth therapists' application of Schroth for adolescents with idiopathic scoliosis (AIS), Part 2, an interview of Schroth therapists to explore the factors that influence their application of Schroth worldwide.

Figure 1 .
Figure 1.Flowchart of participant inclusion through the study: Part 1, a survey of Schroth therapists' application of Schroth for adolescents with idiopathic scoliosis (AIS), Part 2, an interview of Schroth therapists to explore the factors that influence their application of Schroth worldwide.

Figure 2 .
Figure 2. The characteristics and training background of Schroth therapists and their application of Schroth for adolescents with idiopathic scoliosis including.This figure shows the proportion of Schroth therapists that implement the recommendations for physiotherapeutic scoliosis specific exercises (PSSE) as per a SOSORT guidelines.a SOSORT is the International Society of Scoliosis Orthopedic and Rehabilitation Treatment.b PSSE is physiotherapeutic scoliosis specific exercises.

Figure 3 .
Figure 3. Cues, corrections, and techniques that are implemented by Schroth therapists worldwide when delivering Schroth exercise prescription to adolescents with idiopathic scoliosis.

Figure 4 .
Figure 4. Strategies to adjust exercise difficulty of the exercise program that are implemented by Schroth therapists worldwide when delivering Schroth exercise prescription to adolescents with idiopathic scoliosis.

Figure 3 .
Figure 3. Cues, corrections, and techniques that are implemented by Schroth therapists worldwide when delivering Schroth exercise prescription to adolescents with idiopathic scoliosis.

Figure 4 .
Figure 4. Strategies to adjust exercise difficulty of the exercise program that are implemented by Schroth therapists worldwide when delivering Schroth exercise prescription to adolescents with idiopathic scoliosis.

Figure 4 . 30 Figure 5 .
Figure 4. Strategies to adjust exercise difficulty of the exercise program that are implemented by Schroth therapists worldwide when delivering Schroth exercise prescription to adolescents with idiopathic scoliosis.J. Clin.Med.2023, 12, x FOR PEER REVIEW 9 of 30

Figure 6 .Figure 5 .
Figure 6.Support material provided to adolescents with idiopathic scoliosis by Schroth therapists

Figure 5 .
Figure 5. Factors affecting prescription and attendance at the clinic when Schroth therapists are delivering Schroth exercise prescription to adolescents with idiopathic scoliosis.* Stiffness of the curve, as defined by ability of the hump to reduce in size with particular movements.** Hypermobility was defined by Beighton's score 6 or more out of 9. *** Muscle tightness was described as a positive Thomas test or straight leg raise <90 degrees.ADHD is attention deficit hyperactivity disorder.

Figure 6 .
Figure 6.Support material provided to adolescents with idiopathic scoliosis by Schroth therapists worldwide, implementing Schroth to these patients.

Figure 7 .
Figure 7. Compliance monitoring techniques used by Schroth therapists worldwide when delivering Schroth to adolescents with idiopathic scoliosis.

Figure 6 .
Figure 6.Support material provided to adolescents with idiopathic scoliosis by Schroth therapists worldwide, implementing Schroth to these patients.

Figure 5 .
Figure 5. Factors affecting prescription and attendance at the clinic when Schroth therapists are delivering Schroth exercise prescription to adolescents with idiopathic scoliosis.* Stiffness of the curve, as defined by ability of the hump to reduce in size with particular movements.** Hypermobility was defined by Beighton's score 6 or more out of 9. *** Muscle tightness was described as a positive Thomas test or straight leg raise <90 degrees.ADHD is attention deficit hyperactivity disorder.

Figure 6 .
Figure 6.Support material provided to adolescents with idiopathic scoliosis by Schroth therapists worldwide, implementing Schroth to these patients.

Figure 7 .
Figure 7. Compliance monitoring techniques used by Schroth therapists worldwide when delivering Schroth to adolescents with idiopathic scoliosis.
[sic]   completely understand what they have to do in every exercise...I use gravity as an additional challenge. . .Depends on the curve and what their body is capable of doing.(P2, female, Europe, Both ISST and BSPTS, 5 years experience) The personality of the child "...if I'm too pushy, I'm afraid that they will pull back, and then we have nothing...they will pull back out of exercise... [I try] to be very careful when I talk to them..." (P2, female, Europe, Both ISST and BSPTS, 5 years experience)

Theme 2 :
The adolescent-parent relationship Participants highlighted how the parent-child relationship and the motivation of the parents influenced Schroth program prescription.Exercise prescription and attendance was aided when parents had empathy and understanding of their experience."Ithink we have to teach the parents also to see the importance of the situation and I always think about what the adolescent is going through with that."(P6, female, South America, ISST, 2 years' experience) Emotional support provided by the parents."Ihave [sic] problems with the parents' relationship with the adolescent. ..whenI see this happening, I treat them without the parents. .." (P5, Female, South America, BSPTS, 8 years' experience)

J 30 Figure 8 .
Figure 8.The Schroth journey for the adolescent with idiopathic scoliosis (AIS) can be convoluted and not straightforward.The journey can often change.This figure demonstrates how the adolescent may start off their Schroth exercise prescription along one path, for example with exercises and no bracing, and then that may change where bracing is implemented.Child: the adolescent with idiopathic scoliosis.Boat: the parents/guardians.Paddle: the therapist directing the journey.Water system: the system that needs to be navigated along the journey, which can change (the Schroth journey can be challenging to navigate, and treatment can change with time).

Figure 8 .
Figure 8.The Schroth journey for the adolescent with idiopathic scoliosis (AIS) can be convoluted and not straightforward.The journey can often change.This figure demonstrates how the adolescent may start off their Schroth exercise prescription along one path, for example with exercises and no bracing, and then that may change where bracing is implemented.Child: the adolescent with idiopathic scoliosis.Boat: the parents/guardians.Paddle: the therapist directing the journey.Water system: the system that needs to be navigated along the journey, which can change (the Schroth journey can be challenging to navigate, and treatment can change with time).
(a) I only use the BSPTS method (b) I only use the ISST method (c) I use a combination of the BSPTS and ISST methods.

23 . 24 . 25 .
Please specify the average frequency of exercise participation that you recommend for their home exercise program?Please specify the average duration of exercise that you recommend for each home program?How many Schroth exercises do you give your patients to practice at home in the first week?
factors for progression of a curve influence your therapy prescription?If so, how? 9. (a) Explain how you try to keep a child motivated.(b) Do you think this is successful?(c) Why or why not? 10.How do you decide where to start when prescribing exercises to an adolescent with Idiopathic Scoliosis?11.How do you develop the plan for the adolescent with idiopathic scoliosis?Hint if necessary: Do the family and patient collaborate with you to establish the plan?Do you recommend a particular dosage for all?Are you directed by someone else to make decisions?12. How do you decide which Schroth exercises to prescribe?13.How does your Schroth training influence the dosage or therapy that you prescribe for your patients?14.How closely do you stick to what you were taught versus what you actually do?Thank you for your participation in this interview.Do you have any final questions or comments for me?

Table 1 .
Demographic characteristics of survey and interview participants.
a n = 153 due to 20 missing responses.b BSPTS is the Barcelona Scoliosis Physical Therapy School.c ISST is International Schroth Three-Dimensional Scoliosis Therapy.d PSSE is physiotherapeutic scoliosis specific exercises.e n = 166 due to 7 responses missing.f n = 164 due to 9 responses missing.

Table 2 .
General characteristics of program.
Please fill in the table below as to how often the following factors affect your choice of exercise for your patients.Please fill in the table below in relation to how often the following factors influence the frequency of patient attendance at the clinic: Please fill in the table below to indicate how frequently you prescribe the following exercises or features in your programs.Which sport do you think is the most helpful for patients with scoliosis?How often do you include or encourage the following in your exercise programs that you prescribe for adolescents with AIS?
The presence of hypermobility, e.g., Beighton's score 6 or more out of 9The presence of muscle tightness, e.g., hamstring straight leg raise <90 degrees or positive Thomas test Size of the curve/s Location of the curve/s, e.g., thoracic versus lumbar curve