Translation, reliability, and validity of the German version of the Activity Patterns Scale (APS) in musculoskeletal pain: a methodological study

Abstract

In musculoskeletal pain (MSP), pain duration, disability, and mental health relate to how a person engages in daily activities. The self-reporting questionnaire Activity Patterns Scale (APS) assesses these activity patterns and their subscales: Pacing (Pacing to increase activity levels,Pacing to conserve energy for valued activities,Pacing to reduce pain); Avoidance (Pain avoidance,Activity avoidance); Pacing (Excessive persistence, Task-contingent persistence, Pain-contingent persistence). This investigation translated the APS into German and estimated its internal consistency, test-retest reliability, and construct validity. The APS translation was conducted following international guidelines for the transcultural adaptation of self-reported measures. For the construct validity, the Avoidance Endurance Fast-Screening (AE-FS), Tampa Scale of Kinesiophobia (TSK), and Coping Strategies Questionnaires (CSQ) scales were employed. Sixty-five participants with MSP contributed to a baseline survey with a follow-up at two weeks. The German version of the APS subscales demonstrated good internal consistency (Cronbach’s alpha = 0.670-0.89) and satisfactory test-retest reliability (intraclass correlation coefficient = 0.72-0.82); only Task-contingent persistence revealed a poor result. Construct validity was supported by significant correlations between APS subscales (pacing, avoidance, persistence) with related measures, including the Coping Strategies Questionnaire (0.27 to 0.40; -0.50 to 0.55; 0.27 to 0.50), the Tampa Scale for Kinesiophobia (0.28 to 0.47; 0.36 to 0.37; 0.38), and Avoidance-Endurance Fast Screening Pain Persistence Scale (none; none; 0.40). The findings demonstrate high construct validity by the substantial correlations in the predicted directions for the APS subscales and their corresponding questionnaires. The German version of the APS is a reliable and valid tool for assessing activity pattern subscales in individuals with MSP. This distinction could refine research and customize treatment instructions to regulate people’s activity in clinical practice.

Introduction

Musculoskeletal pain (MSP) is the second most common reason for seeking medical care worldwide [1, 2]. MSP can arise from various musculoskeletal structures, such as muscles, joints, ligaments, or tendons, and it may present as localized, regional, or widespread pain [3]. Acute MSP typically originates from nociceptive sources [4]. Usually, nociceptive pain resolves within a few weeks; however, the pain persists beyond the anticipated healing period in some cases. The transition from acute to persistent pain remains incompletely understood [5]. The process may be influenced by an individual’s daily activities, which can be categorized into activity patterns: pacing, avoidance, and persistence [6]. Each pattern represents beliefs and behaviors that influence individuals’ daily occupations. Therefore, activity patterns should be viewed as multidimensional constructs that are not inherently adaptive or maladaptive [7]. These patterns play a significant role in the development and perpetuation of chronic pain. Individuals may use these activity patterns to enhance their functioning, modify their activities to reduce pain, or employ both strategies [8].

Pacing is anticipated to positively influence pain and function as it involves adaptive behavior, alternating between activity and rest [7, 9]. It involves breaking activities into smaller tasks, taking breaks during activity, or adjusting the pace of activities [7, 10]. Therefore, pacing is considered an essential pain management strategy [7]. However, its outcomes are subject to controversy in the context of activity patterns [11,12,13,14]. A meta-analysis examined the relationship between activity patterns and functioning in individuals with chronic pain [9]. Contrary to general expectations, pacing was associated with higher levels of pain and disability, although these individuals exhibited normal psychological functioning [9]. Avoidance is the most well-established pattern in the literature [15]. Distinctive to the avoidance pattern is an individual’s apprehension regarding exacerbating pain or re-injury during certain activities. Consequently, there may be a decrease in both physical and social activities, potentially leading to deconditioning [16]. Extensive research in MSP consistently links avoidance behavior with decreased physical and psychological functioning and increased pain intensity, distinguishing it from other activity patterns [9, 10, 17]. Individuals exhibiting persistence either continue tasks despite experiencing pain or engage in overactivity, characterized by excessive persistence. The assumption that persistence contributes to the development and perpetuation of persistent pain yields inconsistent findings across studies [8,18]. Some studies report positive correlations between measures of persistence and disability, as well as pain [18], while others describe opposite associations [7, 9, 19, 20]. Persistence often leads to a delayed increase in pain, followed by reduced activity, resulting in a typical yo-yo pattern [13, 21]. With repeated experiences of pain flares, activity levels may decrease, potentially initiating avoidance behavior [11]. Therefore, it is plausible for persistence and avoidance to coexist within an individual [13, 15].

It is increasingly evident that understanding the role of activity patterns in disability and MSP is essential [12], particularly in discerning their impact on physical and psychosocial functioning [22]. Thus, having an appropriate measurement tool to identify predominant activity patterns in individuals with MSP is crucial. Kindermans et al. [23] conducted factor analyses using items from existing measurement instruments and identified several activity patterns. Subsequently, Esteve and colleagues developed the Activity Patterns Scale (APS) based on these findings [7]. The APS comprises three scales that classify activity patterns according to their goals, each containing multiple subscales for further delineation. The original Spanish version of the APS demonstrated good validity in assessing activity patterns [7] and has been beneficial for clinicians assisting individuals with pain [24]. The advantage of the APS over existing measures is that it examines distinct concepts for each activity pattern. In addition, the APS allows for the simultaneous examination of multiple activity patterns, challenging the assumption that individuals adopt a single approach to activity [24]. This study aimed to translate the APS into German, adapt the version, and investigate its psychometric properties (construct validity, internal consistency, and test-retest reliability) in individuals with MSP.

As per COSMIN guidelines [25], we expected the APS to exhibit good construct validity. Our hypothesis posits a positive correlation between the APS-pacing subscales and the increasing pain behavior subscale of the Coping Strategies Questionnaire (CSQ), the APS-avoidance subscales demonstrate positive correlations with the Tampa Scale for Kinesiophobia, and the APS-persistence subscales exhibit positive correlations with the Avoidance-Endurance Fast Screening Scale and negative correlations with the Tampa Scale for Kinesiophobia.

Methods

The activity pattern scale

The Activity Patterns Scale (APS) designed to assess activity patterns comprises 24 items; activity performance is quantified using a 4-point Likert scale, ranging from 0 “not at all” to 4 “always” [7, 26].

APS-Pacing: This scale includes three goal-related subscales: Pacing to increase activity levels,Pacing to conserve energy for valued activities, and Pacing to reduce pain. Pacing appears multidimensional; thus, measures that address a specific pacing behavior should be developed with a single goal [27]. The pacing behaviors: breaking tasks into smaller, manageable tasks, taking frequent short rests; and slowing down have been applied to design the subscales [7].

APS-Avoidance: This scale distinguishes between two subscales: Pain avoidance and Activity avoidance. Pain avoidance refers to behavior in the presence or anticipation of changes in pain, while activity avoidance refers to the patients’ condition of being in pain rather than the pain itself.

APS-Persistence: This scale comprises three subscales: Excessive persistence,Task-contingent persistence,and Pain-contingent persistence. Various patterns of persistence have been identified: excessive persistence involves doing too much, disregarding physical limits, and facing the consequences of increased activity levels; task-contingent persistence is characterized by completing tasks or activities despite experiencing pain; and pain-contingent persistence is determined by the level of pain experienced, causing activity levels to fluctuate over time accordingly [24]. The subscales of the Spanish Version showed a satisfactory internal consistency for pacing to increase activity levels (α = 0.76), Pacing to conserve energy for valued activities (α = 0.83), and Pacing to reduce pain (α = 0.76); Pain avoidance (α = 0.80), and Activity avoidance (α = 0.73); Excessive persistence (α = 0.73), Task-contingent persistence (α = 0.83), Pain-contingent persistence (α = 0.82) [7].

The translation and cross-cultural adaption process of the activity patterns scale

The APS translation was conducted following international guidelines for the transcultural adaptation of self-reported measures [28]. Initially, two Spanish-German speakers independently translated the original Spanish APS into German. One translator, a physiotherapist familiar with the concepts, and the other, a professional translator without a medical background, conducted the translations. The translation results were synthesized after a discussion between the translators and an observer. Subsequently, a second professional translator without a medical background performed the back-translation. A committee of physiotherapists knowledgeable about the concept and the back translator collaborated to determine the pre-final German version of the APS. This version has maintained the same instructions, the same content of the items and the same formatting as the original Spanish version (see Supplementary material A: The German version of the APS). The pre-final version underwent pre-testing with a small sample of five subjects who completed the questionnaire and provided simultaneous feedback on their perceptions of the items.

Participants and procedures

The reliability and validity study, including a follow-up, was conducted in the German-speaking part of Switzerland, adhering to the proposed COSMIN recommendations [25]. Based on the initial study, we assumed strong correlations (rs > 0.4) for the criterion validity [7, 29]. We estimated a sample size that would provide 80% power for a two-tailed test of a single Spearman coefficient at a significance level of 0.05, resulting in a sample size of N = 60 [30]. The participants were recruited from six different physiotherapy practices, where physiotherapists informed their patients about the study and provided them with information material. Additionally, recruitment efforts included distributing flyers at a sports center and among bike club members. Data collection and management for the online survey were facilitated through the web application Redcap. Participants accessed the survey via a link or QR code provided on the information material, enabling them to complete it on a PC or smartphone. Only individuals meeting the eligibility criteria were approached. These criteria included: [1] experiencing musculoskeletal pain, the study was not imposing limitations regarding pain intensity or duration, i.e., acute or chronic pain; [2] being over 18 years old; [3] being proficient in German; and [4] consenting to participate by signing the study’s informed consent form. Exclusion criteria comprised: [1] severe diseases such as malignant tumors and [2] neurological diseases like Multiple Sclerosis. Participants had to answer questions about these exclusion criteria before beginning the survey. The online survey was administered twice. Two weeks following the baseline survey, participants received an automated email prompting them to complete the follow-up measurement. A reminder was sent three days later if the survey remained incomplete. The Medical Ethics Committee of the Canton of Zurich, Switzerland, approved the study protocol (BASEC-No. 2016-02,096). All participants provided informed consent before the start of the examination.

Measures

Data collection encompassed demographic variables such as sex, age, profession, and pain location (body part). Participants rated their pain intensity as present, average, and maximum pain experienced over the last week using a Numeric Rating Scale (NRS) ranging from 0 to 10. The average of these three NRS values constituted the overall pain intensity score [31]. Subsequently, participants were required to complete the following questionnaires in German:

• Avoidance-Endurance Fast-Screening (AE-FS) [32]: The AE-F is a short version of the Avoidance-Endurance Questionnaire [19] and is a reliable and valid instrument for classifying activity patterns [22]. The AE-FS includes two scales. First, the Pain persistence scale features seven items. Each item is measured on a 7-point Likert scale ranging from 0 “never” to 6 “always”. The second scale consists of the screening for depressive mood, the two-item Depression Mood Scale (DMS), using items 4 (loss of pleasure) and 13 (indecisiveness) from the Beck Depression Inventory [33]. For each mood item, two statements are provided with scores of 0 “agree” and 1 “don’t agree”. The DMS resulted in a sensitivity of 0.82 and a specificity of 0.92 with an AUC of 0.87 (95% CI 0.80–0.94). The following subgroup classification is based on the two scales: pacing (Pain persistence scale score < 3, DMS < 2), avoidance (Pain persistence scale score < 3, DMS = 2), and persistence (Pain persistence scale score ≥ 3) [32].

• Tampa Scale of Kinesiophobia (TSK): The 11-item TSK measures fear of movement/(re)injury [34]. It measures each item on a 4-point Likert scale ranging from 1 “strongly disagree” to 4 “strongly agree”, and calculates a score between 11 and 44, with a higher score indicating greater fear of movement. The TSK has demonstrated good reliability and acceptable concurrent validity in patients with chronic pain [34].

Coping Strategies Questionnaire (CSQ) [35]: The CSQ is a reliable measure of pain coping strategies and consists of six subscales. Each QCS subscale consists of six items measured on a numeric rating scale ranging from 0 “ never do that” to 6 “always do that”, with a score ranging from 0 to 36, with a higher score indicating how often the strategy is used to cope with pain. We assessed the following four scales. (1) CSQ-increasing pain behavior represents a strategy influencing pain with activities like showering or walking, and taking a break; (2) CSQ-ignoring pain sensations contain items for behavior neglecting pain; (3) CSQ-catastrophizing includes items with catastrophizing thoughts, and (4) CSQ-coping self-statements includes items dealing with pain in the form of self-statements (e.g., “No matter how bad it gets, I know I can handle it.“) [35].

Assessments of activity patterns

Activity patterns were evaluated using the Activity Pattern Scale (APS). To ensure accurate grouping, the AE-FS was utilized. No additional German questionnaires suitable for confirming precise classification were known to us. Fleiss’ kappa was computed to assess the agreement between the AE-FS and APS assessments.

Validation of the activity patterns scale

For the validation of the APS, the following steps were carried out:

(1) The internal consistency was evaluated by calculating Cronbach’s alpha for the APS scales and subscales. The Standard Error of Measurement (SEM) reflects the error expected in a test score due to the test’s imperfect reliability. It estimates the degree to which an observed score may differ from the true score.

(2) The test-retest reliability was computed based on participants who completed the APS retest within two weeks.

(3) The construct validity of the APS-pacing subscales (Pacing to increase activity level,Pacing to conserve energy,Pacing to reduce pain) was assessed by their correlation to the AE-FS-pain persistence scale and the CSQ-increasing pain behavior. The APS-avoidance subscales (Pain avoidance,Activity avoidance) were validated by their correlation to the TSK, the CSQ-catastrophizing, and the AE-FS-pain persistence scale. Lastly, the APS-persistence subscales (Excessive persistence,Task-contingent persistence,and Pain-contingent persistence) were correlated with the AE-FS-pain persistence scale, CSQ-ignoring pain sensations, and CSQ-coping self-statements.

Data analyses

All statistical analyses were conducted using SPSS 29 with a significance level set at 0.05. Descriptive statistics were computed for the variables described, with appropriate measures applied based on the scale level of each variable. The respective participant’s score was excluded from further analysis in cases of missing values. Then, Cohen’s kappa statistic was utilized to assess agreement between categorical outcomes (i.e., assessments of activity patterns between the APS and the AE-FS). Internal consistency of the APS-pacing, APS-avoidance, and APS-persistence scales and their respective subscales was evaluated using Cronbach’s alpha coefficient. Test-retest reliability was assessed using the Intraclass Correlation Coefficient (ICC). Two measurements were necessary for this calculation with a width of 0.2 of the 95% confidence interval [36]. Reliability values were interpreted as follows: less than 0.5 for poor reliability, 0.5 to 0.75 for moderate reliability, 0.75 to 0.9 for good reliability, and greater than 0.9 for excellent reliability [37]. Although the ICC is primarily designed for interval/ratio data, it can be applied to ordinal data when intervals between the applied scales are assumed to be equivalent [38]. Construct validity was evaluated through Spearman rank-order correlation (rs) between the APS scales and their subscales and corresponding questionnaires, including the AE-FS-pain persistence scale, TSK sum score, and the applied CSQ subscales. According to Cohen’s criteria, the correlation coefficient rs interpret values of 0.10, 0.30, and 0.50 as small, medium, and large effects, respectively [29, 39].

Results

The sample consisted of sixty-five participants, with a mean age of 48.42 years (range 19–84). Among them, 38 individuals (58%) identified as female. Two participants were excluded from the study due to a neurological condition. Sixty-three participants completed the baseline survey; 50 (77%) completed the APS retest. Half of the participants reported experiencing pain for more than one year. Additional demographic and clinical characteristics are provided in Table 1.

Table 1 Demographic data and clinical characteristics

Sixty-three participants completed the APS. Table 1 presents the results of the APS. According to the AE-FS classification, 14% exhibited a pacing pattern, 11% demonstrated an avoidance pattern, and 69% displayed a persistence pattern. Cohen’s kappa statistics were conducted to assess the agreement between the assessment of activity patterns using the AE-FS and the APS. The analysis revealed fair agreement, with κ = 0.248 (95% CI: 0.173 to 0.324), p < 0.001.

Reliability analysis

For reliability analysis, Cronbach’s alpha was calculated to assess the internal consistency of the APS. Table 2 presents the data on the reliability of the APS scales and subscales. The APS-Pacing showed a good Cronbach’s alpha of 0.91, yielding a Standard Error of Measurement (SEM) of 0.21. The SEM indicates that the observed scores vary from the true scores by approximately ± 0.21 points. In assessing the scale’s internal consistency, all items were found to have a corrected item-total correlation greater than 0.50. As a result, no item removal was necessary, as none would have increased Cronbach’s alpha, see Table 3. The APS-avoidance had a good Cronbach’s alpha of 0.77, with an SEM of 0.32. The corrected item-total correlation was greater than 0.40; no item removal would have increased Cronbach’s alpha. A moderate Cronbach’s alpha of 0.67 and an SEM of 0.28 were calculated for the APS-persistence. The corrected item-total correlation for items 2,10, and 21 of the Task-contingent persistence was less than 0.20; removal of these items would slightly improve Cronbach’s alpha of 0.71 for the APS-persistence scale.

Table 2 Reliability analysis of the APS and their subscales

Regarding test-retest reliability, an overall Intraclass Correlation Coefficient (ICC) of 0.84 (95% CI [0.75, 0.90]) was observed. The ICC was deemed good for the APS-pacing scale (ICC = 0.82, 95% CI [0.72, 0.88]), as well as for APS-avoidance (ICC = 0.77, 95% CI [0.65, 0.85]), and moderate for APS-persistence (ICC = 0.72, 95% CI [0.59, 0.82]). However, Task-contingent persistence within the APS exhibited poor ICC (ICC = 0.46, 95% CI [0.24, 0.63]), while all other subscales demonstrated moderate to good test-retest reliability.

Table 3 Internal consistency of the German activity pattern scale in people with musculoskeletal pain

Validity analysis

Spearman’s rank-order correlations were employed to investigate the relationship between the APS scales and the corresponding questionnaires. The results are summarized in Table 4. Significant medium correlations were observed between the APS-pacing subscales and the TSK, CSQ-increasing pain behavior, and CSQ-catastrophizing. Notably, the APS-pacing subscales consistently exhibited similar correlations across all analyses.

Table 4 Correlations between the APS scales and associated questionnaires

Significant moderate positive correlations were observed between the APS-avoidance subscales with the TSK. Specifically, Pain avoidance showed large negative associations with CSQ-ignoring pain sensations and CSQ-coping self-statements. In contrast, Activity avoidance correlated significantly with CSQ-increasing pain behavior and CSQ-catastrophizing. Regarding APS-persistence subscales, uniform correlations were not observed. Excessive persistence correlated significantly only with CSQ-catastrophizing. Task-contingent persistence positively correlated with the AE-SF-pain persistence scale and CSQ-coping self-statements. Pain-contingent persistence demonstrated strong correlations with the CSQ-catastrophizing and medium effects for the TSK, CSQ-increasing pain behavior, and CSQ-coping self-statements.

Discussion

The way individuals with MSP engage in their daily activities can significantly affect the duration of MSP, the level of disability, and mental health. The use of standardized questionnaires to assess activity patterns is crucial for developing personalized treatment approaches for individuals with MSP. This study translated the APS into German and evaluated its internal consistency, test-retest reliability, and construct validity. The reliability and construct validity of the German translation of the APS were found to be satisfactory in this study. The findings indicate that the German version of the APS has satisfactory reliability and construct validity, suggesting it is a valid tool for assessing specific subscales of activity patterns. Unlike other instruments, the APS allows for the simultaneous assessment of multiple activity patterns.

Assessment of activity patterns

The impact of pain-related activity patterns on disability and pain in individuals with musculoskeletal injuries has been extensively documented [40]. Recognizing the approach toward daily activities in individuals experiencing pain may enhance the development of future treatment approaches [22]. This study found that most participants, based on their scores in the AE-FS, were classified into the persistence pattern, with only a minority displaying avoidance or pacing behavior. In contrast, the APS assessment of activity patterns revealed that participants could show similar values at different subscales. This finding supports the assumption that activity patterns are interconnected, and individuals may simultaneously employ various approaches toward activity [7, 40].

Therefore, the assessment of activity patterns based on the German translation of the APS showed only fair agreement with the categorization of the AE-FS. While the AE-FS is valid for classifying activity patterns, it primarily measures pain persistence and utilizes depressive mood for further differentiation [22]. Consequently, incorporating the APS into personalized treatment approaches may offer the advantage of obtaining a more comprehensive understanding of an individual’s approach to daily activity [20]. Moreover, these findings could enhance future research on the topic and contribute to a better understanding how individuals engage in daily activities while experiencing pain.

Reliability

While our results indicated excellent internal consistency and test-retest reliability for the APS-pacing and APS-avoidance subscales, the findings for the APS-persistence subscales were less conclusive. The calculations revealed only moderate internal consistency and test-retest reliability, with a particularly weak result for Task-contingent persistence. These findings suggest that a rewording of these items may be necessary for future applications of the APS. It’s worth noting that the original Spanish APS showed similar internal consistency for the avoidance and pacing scales. However, test-retest reliability was not investigated, preventing a direct comparison [7].

Construct validity

We found solid evidence to support the construct validity of the German-translated APS [41]. Most of the hypotheses based on previous research on the APS were supported [7], except the hypothesis regarding the expectations of a negative correlation between persistence subscales and the TSK.

How does the APS compare with assorted questionnaires assessing pain-related activity? Although the three pacing subscales pursue different goals [27], they all revealed significant positive correlations with scales assessing strategies to minimize pain exacerbation with activities, catastrophizing, and kinesiophobia. These associations suggest engaging in behaviors that should minimize the exacerbation of pain [9]. Pain catastrophizing involves exaggerating pain experiences, ruminating on them excessively, and feeling helpless [42]. Finally, kinesiophobia can result in an excessive, irrational, and debilitating fear of movement or physical activity [34]. A notably larger correlation was observed for the subscale Pacing for pain reduction with kinesiophobia. This association highlights pain avoidance tendencies, while the other pacing subscales center around activity regulation [27]. Actually, the consistency of activity has emerged as the most advantageous aspect of persistence [43].

Consequently, the subscales Pacing for increasing activity level and Pacing for conserving energy for valued activities appear to share similar approaches [6, 23, 44]. In fact, the initial study by Esteve and colleagues demonstrated positive associations between these two subscales and daily functioning, suggesting that individuals with a more realistic interpretation of their situation benefit from activity-related pacing compared to those driven by unfounded fears of pain intensification [7, 20]. Individuals who engage in pacing strategies focused on adjusting activity levels or conserving energy for valued activities might maintain a more realistic understanding of their situation and experience better daily functioning. Pacing to reduce pain on the other side could be interpreted as a reactive strategy to alleviate pain [23, 45]. Such assumptions underscore the importance of monitoring pacing strategies [40]. The findings further indicate that individual pacing behavior can be assessed based on the goals of persons with MSP when utilizing the Activity Pattern Scale (APS). This approach would acknowledge the diverse motivations behind pacing behavior and highlight the need for tailored assessments to effectively address the needs of individuals with MSP.

The two avoidance subscales showed diverse associations with the selected questionnaires, except for kinesiophobia. The Pain avoidance subscale revealed a negative correlation between ignoring pain sensations and a comparatively weaker association with dealing with pain through self-statements. This finding suggests that individuals scoring high on the Pain avoidance subscale are less likely to ignore pain sensations but may struggle with effectively managing pain through positive self-talk or coping statements [8]. This pattern is reflected in their approach toward daily activities, where they remain attentive to changes in pain [40]. Consequently, they may avoid engaging in certain activities due to the consistent presence of pain sensations or the fear associated with them. Both Pain avoidance and Activity avoidance were positively associated with kinesiophobia, which evaluates beliefs about pain and activity avoidance due to fear of pain increasing or indicating a serious medical issue [34, 42]. Notably, Activity avoidance was strongly linked to negative appraisals of activity, particularly catastrophizing. This pattern of thinking leads individuals to prefer reducing activity to avoid pain rather than adopting effective pain management strategies [46]. The findings emphasize that negative appraisals often influence activity avoidance in pain management [40]. These findings underscore the importance of accurately assessing and distinguishing between these two avoidance patterns in pain management interventions [23]. Mainly, while Activity avoidance remains a significant predictor of disability, Pain avoidance is only marginally related to activity impairment [7]. These findings suggest that addressing activity avoidance may be particularly important in mitigating disability associated with pain, and the APS might be an essential tool for this purpose.

The concept of persistence is multifaceted and the correlations of the three subscales reflect this complexity. Excessive persistence showed significant associations only with catastrophizing. This pattern, described as pushing oneself to continue activities beyond one’s limits, was found to correlate positively with negative affect and daily functioning [10], akin to pain catastrophizing. It has been suggested that individuals who attempt to counteract negative emotional states may engage in excessive levels of activity [8], potentially leading to long-term exacerbation of pain and disability [13]. This behavior underscores the intricate relationship between psychological factors, activity levels, and pain experiences, emphasizing the necessity for thorough assessment and intervention strategies in pain management.

Task-contingent persistence refers to individuals continuing activities despite pain until the task is completed. This pattern showed a strong correlation with the pain persistence scale and with coping with pain through self-affirming statements of capability. In individuals with fibromyalgia and low back pain, Task-contingent persistence has demonstrated positive associations with daily functioning, negative associations with impairment, and a robust positive correlation with positive affect [24, 47]. Therefore, it is suggested that this activity pattern represents the most adaptive behavior due to motivational mechanisms: Individuals persist in activities due to their perceived value, linked to heightened feelings of control over pain, self-efficacy, and positive affect [23]. Pain-related persistence entails engaging in activities until pain intensity becomes too severe, thereby adjusting the level of activity based on the current pain level. This approach to activity and pain shares similarities with kinesiophobia and catastrophizing, which may explain the observed significant correlations with these scales. In addition, Pain-related persistence also showed an association with behaviors that exacerbate pain and with dealing with pain through self-statements. Similar correlations have been reported for pacing subscales, indicating similarities in activity approaches.

To conclude, the construct validity supports the various approaches toward activity and pain management for individual behavior as defined by the subscales. Furthermore, the study highlights the complexity of these patterns and their potential impact on pain management [44]. These results showed that the pacing, avoidance, and persistence subscales are best conceived as multidimensional constructs and that the dimensions underlying these constructs should be distinguished. Understanding these functions of activity patterns is essential for rehabilitation professionals working with individuals with MSP. It enables targeted interventions and personalized treatments and promotes self-management strategies that empower individuals to effectively manage their pain and improve their overall quality of life.

Limitations

While the analyses presented in this paper supported the construct validity of a culturally adapted German version of the APS, this study has some limitations. First, activity patterns describe a person’s goals and approach to daily activities when MSP interferes. Indeed, the questionnaires were developed for persons with persistent pain [23, 44, 48]. Although the majority of the study participants reported persistent MSP for longer than three months, participants were heterogeneous regarding the duration of pain, age range, and pain intensity. This heterogeneity might have limited the construct validity. In the future, APS subscales should be compared between groups with acute, subacute, and persistent MSP, preferably in a longitudinal setting. Furthermore, a limited amount of German questionnaires assessing pain-related activity were available, which may have diminished the significance of the construct validity. We could not measure structural validity due to an insufficient sample size. Further research is needed to conduct confirmatory factor analysis (CFA) to validate the structure of the APS. Additionally, future studies should explore the relationship between the APS subscales and pain, physical, and psychosocial impairments.With these considerations in mind, slight adaptations to the APS scales and their eight subscales may be warranted based on a clearer understanding of activity patterns.

Conclusion

This study demonstrated that the German version of the APS effectively assesses individuals with MSP into pacing, avoidance, or persistence subscales. Its psychometric properties are comparable to the original Spanish version, making it a promising tool for clinical and research applications. The availability of the German version may encourage studies in German-speaking countries to delve more into activity patterns among individuals with MSP, thereby facilitating the customization of treatment strategies to regulate activity levels. The potential long-term benefit lies in developing personalized rehabilitation programs tailored to the unique needs of individuals with MSP. We believe that our findings and the German-translated APS make a valuable contribution to this discourse.