Adaptation and validation of a scale of self‐efficacy and social support for physical activity in Spanish patients with severe mental disorders

Abstract Background People with severe mental disorders (SMDs) suffer problems of obesity, a sedentary life, and poor physical condition, mainly due to low levels of physical activity. Self‐efficacy (SE) and social support (SS) are important components that influence participation in physical activity. Methods This study adapted a scale to assess SE and SS in promoting physical activity in Spanish people with SMDs, as well as provide preliminary evidence of its validity. One hundred Spanish patients (23% female) with SMDs, between 26 and 61 years old, completed the SE/SS assessment for SMD (SE/SS‐ASMD). Results The instrument seemed to capture a four‐factor structure in people with SMDs. Due to the lack of a gold standard, the scale was related to other instruments with which it might be expected to show a correlation, such as those for physical activity and its quality; however, the levels of correlation found were low (≈0.3). The Internal consistency (Cronbach's α) for the SE‐ASMD, SS‐ASMD staff, SS‐ASMD peers, and SS‐ASMD family scales were 0.76, 0.76, 0.80, and 0.80, respectively. Conclusions The psychometric analysis of the SE/SS‐ASMD supported its suitability as a new tool for researchers in the area of physical activity among people with SMDs.


| INTRODUC TI ON
The importance of physical activity for the physical fitness and psychological health of individuals with schizophrenia is well established (Carpiniello, Primavera, Pilu, Vaccargiu, & Pinna, 2013;Perez-Cruzado, Cuesta-Vargas, Vera-Garcia, & Mayoral-Cleries, 2018). Unfortunately, many people with schizophrenia remain inactive (Vancampfort et al., 2016), and researchers and clinicians are challenged with how to help them initiate physical activity and maintain it long-term. Previous research has found that one significant contributing factor to inactivity is social isolation (Soundy, Freeman, Stubbs, Probst, & Vancampfort, 2014).
Given this situation, there is a need to develop interventions to promote and foster physical activity in this population. Social cognitive theory (SCT) developed by Bandura has influenced a large amount of research on health behavior and the promotion of physical activity (Ariyabuddhiphongs & Chanchalermporn, 2007;Gao, 2012). Specifically, self-efficacy (SE) and social support (SS) are two important elements of SCT in research of physical activity.
Self-efficacy refers to individual action, in which a person believes in the possibility of achieving a certain desired result, and they can actively direct the course of their lives. The perception of SE is a very important predictor of healthy behavior, as well as self-management of chronic disease (Clark et al., 2015;Willis, 2015). When applied to the practice of physical activity, SE is usually considered to be the optimistic self-belief of being able to overcome perceived challenges. SE has been related to the intention of people to practice physical activity, to strategize in addressing a sedentary lifestyle, and to maintain a regular practice of physical activity (Barz et al., 2015;Bergström, Börjesson, & Schmidt, 2015;Huffman, Pieper, Hall, St Clair, & Kraus, 2015;Plotnikoff, Gebel, & Lubans, 2014). Studies have also indicated that SE correlates with physical activity in adults with SMDs (Bezyak, Berven, & Chan, 2011).
Another important variable in terms of physical activity from the perspective of SCT is SS. Studies have indicated that SS in the general population critically influences the participation of individuals in physical activity (Draper, Grobler, Micklesfield, & Norris, 2015;Mendonça & Farias Júnior, 2015;Zhang et al., 2015). Other studies have also indicated the importance of social interaction in promoting physical activity in those with SMDs (Gray et al., 2014;Hoffmann et al., 2015). SS can come from several different groups, such as family and friends, in various forms, for example, emotional and financial help. Previous reports indicate that the SS received by people with SMDs that contributes to increased exercise comes mainly from three groups, family, professionals, and peers (Citrome & Yeomans, 2005;Daumit et al., 2005).
We studied the relationship between interventions and physical activity in a population that traditionally shows low levels of activity, those with intellectual disabilities. We made use of a previously developed SE and SS for activity scale to measure the effect of these variables on the performance of physical activity (Lee, Peterson, & Dixon, 2010).
A Spanish version of the SE and SS assessment for SMDs (SE/SS-ASMD) should have immense applicability, since Spanish is the third most spoken language in the world. In Spain, 9% of the general population (>400,000 people) suffer from a SMD (Muñoz, Perez-Santos, Crespo, & Guillen, 2009). Therefore, the objective set out in the present study was the adaptation and validation of the SE/SS-ASMD questionnaire for the promotion of physical activity in people with SMDs.

| Participants
The participants were recruited over a six-month period from the mental health service of the Regional University Hospital of Málaga, Spain. A total of 100 adults with a SMD participated in this study and had a set of pathologies with an ICD-10 diagnosis of an affective or nonaffective functional psychotic disorder (codes F20-F22,  Table 1.

| Procedure
The SE/SS-ASMD scale was administered by several qualified therapists. On the same day, the responses of the SE and SS scale were collected, body mass index (BMI), waist circumference and a scale to assess current physical activity (International Physical Activity Questionnaire, IPAQ-Short Version) were also measured.

| Ethics
After receiving project information verbally and in writing, study

| Measures
The and "yes." Together, the three SS scales included 17 items, six family items, six staff items, and five peer items. The SS scales had response options of "no," "yes-sometimes," and "yes-a lot." The EuroQol-5 Dimension (EQ-5D) questionnaire was a brief, multi-attribute, generic, health status measure composed of five questions with Likert response options (descriptive system), and a visual analog scale (EQ-VAS). The latter asked patients to rate their health from 0 to 100 (the worst and best imaginable health, respectively). The descriptive system covered five dimensions of health (mobility, self-care, everyday activities, pain and discomfort, and anxiety and depression) with five levels in each dimension (no problems, slight problems, moderate problems, severe problems, and unable to perform or extreme problems) (EuroQol Group, 1990).
International Physical Activity Questionnaire was a 27-item self-reporting measure of physical activity for use in adults. The scale classified light, moderate and vigorous activity, as well as sedentary behavior, over the previous seven days. Participants had to report how many days per week they had performed physical activity, and the duration in hours and minutes (Craig et al., 2003).  (Schumacker & Lomax, 2004). The CFI varied along a continuum of 0 to 1 in which values ≥0.80 were considered to be a satisfactory fit, and ≥0.95 reflected an excellent fit (Browne & Cudeck, 1992). Only those items whose factor loadings in the EFA were >0.40, a well-known cutoff point of acceptability (Tabachnick & Fidell, 2001), were retained for subsequent analyses. Items with significant cross-loadings were deleted.

| Statistical analysis
To determine the internal consistency of the scale, Cronbach's α coefficients were calculated for each subscale.
The convergent criterion validation referred to the evaluation of instruments that assessed variables that measured similar constructs, or that should show a similar relationship. The relationship of these score with the variables was used to validate the SE/SS-ASMD scale. The Pearson correlation coefficient was used to evaluate convergent validity between the SE/SS-ASMD scale and the EQ-5D questionnaire, and IPAQ.
All statistical analyses were conducted using the Statistical Package for Social Science for Windows version 21.0 and SPSS AMOS.

| Descriptive statistics
The participants were 76% men (76 men and 24 women), and performed an average of 70.82 min per week of vigorous physical activity. Their mean BMI was 29.13, and mean waist circumference was 103.04 cm.
The mean and SD for each of these items are shown in Table 1.

| Exploratory factor analysis (EFA)
The correlation matrix, preliminarily evaluated by Bartlett's sphericity test rejected the null hypothesis of an identity matrix (degrees of freedom, df 253; p < .001), with a KMO sample adequacy measure of 0.78, indicating that the sample was adequate (Pereira, 1999). An eigenvalue >1, a value >10% of the variance and a scree test (Figure 1) were used as criteria for the extraction of factors (Cattell, 1966;Kaiser, 1960).
Based on these conditions, four factors were extracted, fulfilling two of the three criteria (autovalue >1 and curve of the scree test). The total variance explained with the four factors was 70.41%.
The varimax rotation method was used because it guarantees that we did not exclude the possibility of expressing a certain element in a factor, or in more than one factor.

| Reliability
The Internal consistency, Cronbach's α, for the SE-ASMD, SS-ASMD staff, SS-ASMD peers, and SS-ASMD family scales were 0.76, 0.76, 0.80, and 0.80, respectively. With these results, the scale of SE and SS for physical activity seemed to be well adapted to a four-factor model for people with SMDs ( Figure 2).

| Convergent validity criteria
Due to the lack of a gold standard for the evaluation of SE and SS in the practice of physical activity in people with SMDs, there is no tool in the current literature that evaluates these variables in this population, the scale in the current study was compared with the IPAQ (Craig et al., 2003) and with the EQ-5D questionnaire (EuroQol Group, 1990). Table 3

| D ISCUSS I ON
The need to increase the levels of physical activity in people with SMDs has been studied in different places, due to its influence on health in general (Vancampfort, Stubbs, Sienaert, et al., 2015;Vancampfort, Stubbs, Ward, Teasdale, & Rosenbaum, 2015).
Unfortunately, as for the rest of the world, obesity levels in Spain have progressively increased in recent decades (Sánchez-Cruz, as it greatly reduces autonomy and increases the dependence on others for activities of daily living, in addition to the large number of negative effects that it has on physical health (Clerici et al., 2014;Kwan et al., 2014;Opel et al., 2015).

TA B L E 2 Factor loading matrix after varimax rotation
It is vital to use valid and reliable measures that are culturally and linguistically adapted for the target population. The analysis of the psychometric variables of the SE/SS-ASMD scale allowed us to obtain a new tool for researchers in the area of physical activity for people with SMDs, with a great importance attached to SE and SS promoting the inclusion of these people in physical activity programs (Davy Vancampfort, Stubbs, Sienaert, et al., 2015;Vancampfort, Stubbs, Venigalla, et al., 2015).
The adjustment values relating to the SE and SS scales were satisfactory. The determination of a four-dimensional structure using maximum likelihood extraction was consistent with the scale validated in intellectual disability (Cuesta-Vargas et al., 2013). However, some items were loaded in more than one factor, though this might be due to the similarity in the identification of the groups that provided support for the practice of physical activity. Thus, the scale was composed of a dimension about SE for the practice of physical activity and three dimensions related to SS (family, professional and peer

| Limitations
The present study had a series of limitations. The participants in the study population were those with SMDs, so the sample was very heterogeneous, with many psychiatric disorders. The cognitive functions of the participants were not evaluated, so this could have led to bias in their responses to the scale. In addition, there was no gold standard for validation of convergent criteria of the SE/SS-ASMD scale. The lack of longitudinal data also did not allow the assessment of important psychometric properties, such as test-retest reliability or sensitivity to change. The indices were satisfactory for the sample size of 100 participants; however, due to the small sample, it was not possible to divide the sample into two subsamples for separate exploratory factor analysis and confirmatory factor analysis separately.

ACK N OWLED G M ENTS
This project was funded in part by the Instituto de Salud Carlos III (ISCIII) of the Ministry of Economy and Competitiveness (Spain), through the Network for Prevention and Health Promotion in Primary Care (RD16/0007/0012). JVL has a "Miguel Servet" research contract from the ISCIII (CP14/00087).

CO N FLI C T O F I NTE R E S T S
None declared.

DATA AVA I L A B I L I T Y S TAT E M E N T
The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.