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Readiness to adopt adequate postural habits: an application of the Transtheoretical Model in the context of back pain prevention
Patient Education and Counseling 42 (2001) 175–184 www.elsevier.com / locate / pateducou
Readiness to adopt adequate postural habits: an application of the Transtheoretical Model in the context of back pain prevention Stefan Keller a
a,b ,
*, Christoph Herda a , Kai Ridder a , Heinz-Dieter Basler a
Institute for Medical Psychology, University of Marburg, Bunsenstr. 3, 35033 Marburg, Germany b Cancer Prevention Research Center, University of Rhode Island, Rhode Island, USA Received 30 July 1999; received in revised form 15 February 2000; accepted 24 February 2000
Abstract Based on a biomechanical model, an adequate body posture can contribute to the prevention of back pain and back pain chronicity. This study examines the explanatory value of the Transtheoretical Model (TTM) for the adoption of adequate postural habits in a cross-sectional sample of 149 employees of a German administration unit (mean age 40.2 years, 50% female). Using newly developed instruments with satisfactory psychometric properties, basic assumptions of the TTM could be confirmed: self-efficacy and the perceived pros for maintaining a good body posture increased significantly across the stages, while the perceived cons decreased. Additionally, the use of preventive strategies for back pain prevention increased linearly and significantly across the stages of change. The study supports the applicability of the TTM for postural behavior. Considering stages of change as an intervening variable may contribute to clarifying the relationship between participation in low back schools and prevention of back pain chronicity. Longitudinal and intervention study data are needed to support these assumptions. 2001 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Prevention; Posture; Transtheoretical Model; Behavior change
1. Introduction Comprehensive treatment approaches incorporating behavioral, biomedical, psychological, physical, and social components have proven to be most effective in the treatment of chronic pain [1]. Recently, more attention was given to mechanisms that lead from highly prevalent single pain episodes to chronic *Corresponding author. Tel.: 1 49-6421-286-3774; fax: 1 496421-286-4881. E-mail address: [email protected] (S. Keller).
0738-3991 / 01 / $ – see front matter PII: S0738-3991( 00 )00103-8
pain syndromes. Basler [2] describes four factors contributing to pain chronicity: biomechanical stress, psychosocial stress, operant conditioning mechanisms, and dysphoric mood. Consequently, physical exercise, training of posture and activities of daily living, and stress / pain management are seen as crucial intervention modules for the prevention of chronicity [3]. As Turk and Okifuji [4] pointed out, in the process of chronicity psychological and behavioral factors mainly help maintain and exacerbate pain, disability, and psychological distress, whereas biomechanical factors are more relevant to the
2001 Elsevier Science Ireland Ltd. All rights reserved.
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acquisition of pain. This paper will focus on the motivation to adopt behavior relevant to the biomechanical risk factors for pain chronicity. Biomechanical stress of the back can be caused by heavy work like lifting, long-term exposure to vibration, or sedentary or monotonous job functions [5–8]. The biomechanical model of chronic pain assumes a relationship between external strain, body posture, muscle activity, and intravertebral pressure [9]. According to this model, chronic pain is a result of an abnormal pattern of paraspinal activity caused by overexertion and poor postural habits. It is believed that such irregular muscle activity provides abnormal support for the spine, which in turn becomes unstable. The instability of the spine enhances the possibility of impingement upon nerve endings and abnormal pressure on the discs, and thereby produces pain [10]. Support for this model dates back to early studies conducted by Nachemson and co-workers. By means of intradiscular and electromyographic (EMG) measurements, these authors were able to demonstrate that the pressure exerted on lumbar discs as well as the activity of the paraspinal muscles are determined by the position of the spine [10,11]. Recent research has generally confirmed these results [12,13]. An additional risk factor is physical inactivity: it can lead to muscular deconditioning and a loss of muscle strength and to an increased risk for the development of low back pain complaints [14,15]. One way to lower the impact of biomechanical stress is to keep an adequate body posture while performing activities of daily living. Based on the works of Nachemson and colleagues and the Swiss ¨ neurologist Brugger [16] such a ‘physiological posture’ can be conceptualized as consisting of a pronounced lumbar lordosis, an erected thorax with a thoracic kyphosis, and a stretching of the cervical spine. With regard to the overall distribution of pressure in the spinal structures, a pronounced rotation of the pelvis is expected to be most beneficial. In a sitting position, the center of gravity is moved forwards and is located slightly above and ventral from the ischial tuberosities. The findings regarding the importance of biomechanical stress serve as a basis for numerous back school programs which usually follow two principles: education and encouragement to improve body posture as well as to perform an exercise program on
a regular basis. Additional treatment modules may be added, depending on the target group and the intervention setting [17]. However, the empirical evidence for the effectiveness of back schools is not convincing. Attempts to analyze the efficacy of back schools are complicated by the limited methodological quality of some of the original studies [18]. Meta-analyses suggest that, for patients with acute or chronic back pain, back schools show hardly any impact [18], especially when they are offered as a ¨ sole treatment [19]. Maier-Riehle and Harter [20] conclude from their meta-analysis based on 18 controlled studies that positive short-term results can be observed especially for knowledge and backfriendly behavior, but the results are not favorable for clinical variables (e.g., pain intensity) or health economic variables (e.g., utilization of health care services). For the time points more than 6 months after the intervention no positive effect for any of 14 dependent variables could be confirmed. A possible explanation for these findings may be that not enough attention has been paid to the intervening variables: the frequency and intensity of pain episodes and other variables may only be affected if the target behaviors of a back school intervention — adequate body posture and regular physical exercise — are adopted habitually and continuously. To date, little is known about the stability of changes in these behaviors during back school programs or the follow-up periods. Experiences from exercise research show that in spite of the positive effects, 50% of all subjects who begin to exercise will discontinue after 3–6 months [21,22]. With regard to body posture, we could document with a video-supported behavior observation method that participants of preventive back school programs learned to perform a variety of activities of daily living adequately [3,23]. However, the majority of all subjects admitted at the 1-year follow-up that they considerably decreased the frequency and intensity of physical exercises and the awareness towards their body posture [23].
2. The Transtheoretical Model (TTM) Considering these findings, stronger efforts should be made to integrate research for back pain prevention with research about models and methods of
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behavior change. One model that has produced promising results in this context is TTM (also ‘Stages of Change Model’) developed by Prochaska and colleagues [24,25]. The TTM is based on the premise that people move through a series of stages in their attempt to change a behavior. Five stages of change have been reliably identified across health behaviors: precontemplation (PC, no intention to change behavior in the foreseeable future, or denial of need to change); contemplation (C, intention to change within the next 6 months); preparation (PR, serious intention to change in the next 30 days); action (A, initiation of overt behavioral change); and maintenance (M, sustaining behavioral change for 6 months or more). Movement through these stages may not occur in a linear fashion; often individuals move through the stages repeatedly in a cyclical manner before maintenance is reached. The TTM proposes integration of the stages of change with the processes of change, self-efficacy, and decisional balance. The stages represent an organizing structure and a temporal dimension describing when cognitive and behavioral changes occur. The processes of change describe how these shifts occur and are divided into experiential and behavioral processes. Decisional balance focuses on the perceived benefits (pros) and costs (cons) of a behavior, and is important in decision making [26]. The pros and cons are relevant in understanding and predicting transitions between the PC, C, and PR stage. Cons always outweigh the pros of changing a behavior in the PC stage and the opposite is true for the A and M stages. Between the C and PR stages, pros and cons usually intersect [27,28]. Finally, selfefficacy involves one’s confidence that one can perform a behavior required to achieve a certain outcome across a variety of situations. It is also believed to be a critical construct in behavior change [29]. Self-efficacy increases across the stages of change and is an important predictor of stage, especially at the A and M stages [30]. The TTM has been successfully applied to numerous health risk behaviors like smoking cessation, dietary fat consumption, ultraviolet light exposure, alcohol abuse, screening mammography, and others [24,28]. Recent research has also confirmed the validity of the TTM for the adoption of regular exercise [31–33]. The baseline stage of change was found to be a predictor of future exercise behavior;
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self-efficacy increased linearly across the stages; the pros of exercise also increased while the cons decreased between PC and A. While first promising steps have been undertaken to assess the readiness of chronic pain patients to use self-management strategies [34,35], no study has yet focused on the readiness to perform activities of daily living with a body posture that is adequate for the prevention of back pain. The aim of this study is to evaluate the applicability and the validity of core constructs of the TTM for adopting and maintaining an upright body posture during activities of daily living. Based on the findings in other areas, especially for exercise behavior, we expect that subjects can be validly categorized in five stages of change, and that self-efficacy and the perceived pros of good postural behavior increase across the stages while the cons decrease. This implies that the cons are higher than the pros in the PC and lower in the M stages.
3. Methods
3.1. Sample The sample consisted of employees of a large administrative unit (unemployment office) in Germany. All of them were working in offices, predominantly in a sitting position most of the day. Of 180 distributed questionnaires, 149 were returned (response rate 83%). The mean age of the respondents was 40.2 years (S.D. 5 12.3), 50% were females. The level of education was somewhat above the population average, 20% had a university degree; almost all subjects lived with a partner (83%). About 83% indicated that they had ‘never’ or ‘seldom’ experienced back pain in the 2 weeks previous to the assessment.
3.2. Measures 3.2.1. Staging algorithm for maintaining an upright body posture Subjects were staged by the algorithm shown in Table 1. To ensure that all subjects had a comparable concept of a ‘physiological posture’ a short and easy-to-understand definition was presented before the staging questions. Subjects were categorized into the five stages of change (see Table 1). Although the
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Table 1 Staging algorithm for maintaining an upright body posture a For the prevention of back problems it is important to continuously engage in preventive behaviors, not only in certain situations but also in during activities of daily living and leisure time activities. This means, for example, maintaining an upright body posture while sitting or bending your knees when lifting objects from the floor. 1. Do you engage in behaviors to prevent back problems most of the time, i.e., do you consciously maintain an upright body posture? (1) No, and I do not intend to change my behavior. (2) No, but I intend to change my behavior in the next 6 months. (3) No, but I intend to change my behavior in the next 30 days. (4) Yes, I have kept a good body posture, but for less than 6 months. (5) Yes, I have kept a good body posture for more than 6 months. 2. In the last 6 month, have you made any steps to actively deal with the topic of good body posture, like reading a book or watching a TV program about it? Yes No a Scoring: Subjects are categorized into the stages precontemplation (answer (1)), contemplation (2), action (4) or maintenance (5) based on the answers to question 1. Subjects who stage themselves as being in preparation (3) are re-staged into contemplation unless they have already made an attempt to change their behavior according to question 2.
staging algorithm is comparatively short, its usefulness and validity had been confirmed across a variety of other behaviors [25].
3.2.2. Preventive behaviors A scale had been developed in previous studies describing the utilization of behaviors that are considered preventive for the development of back pain. The core of the scale was built by items that had shown to be valid in the context of a controlled back school intervention study with video-based behavior observation [3,23]. Sample items are ‘‘In the previous 2 weeks, I interrupted long sedentary activities and moved for a few minutes.’’ or ‘‘In the previous 2 weeks, I made sure to keep my back straight when vacuuming.’’. Ratings were made on a 5-point Likert scale, ranging from 1 5 ‘never’ to 5 5 ‘always’. The revised 26-item scale had a one-factorial structure explaining 33% of the variance and good psychometric properties (a 5 0.91) [36]. 3.2.3. Self-efficacy On a scale ranging from 1 5 ‘not confident’ to 5 5 ‘extremely confident’, subjects were asked to rate their confidence that they could keep the defined body posture in a variety of situations. The situations included behavioral and cognitive-emotional aspects.
Sample items are: ‘‘How confident are you that you keep an upright body posture when you are sitting at your desk?’’ or ‘‘How confident are you that you show an upright body posture when you are down and depressed?’’. The 20-item scale had a onefactorial structure explaining 30% of the variance and good psychometric properties (a 5 0.92) [36].
3.2.4. Decisional balance The scales to measure pros and cons of keeping the defined body posture most of the time were adapted from a decisional balance measure for exercise described by Marcus et al. [37]. Eleven items describe the pros of the respective behavior (example: ‘‘If I keep an upright body posture I can prevent backpain.’’), and six items the cons (example: ‘‘If I keep an upright body posture I will appear to be arrogant.’’). Subjects rated how important each of these statements is for their decision to show the target behavior. The psychometric properties were good for the pros (a 5 0.89) and satisfactory for the cons (a 5 0.66) [36]. 3.3. Statistical analysis For description purposes, means, standard deviations, and percentages were computed. To account
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for group differences, one-way analysis of variance was used. Follow-up tests were conducted by Tukey’s procedure. Comparisons within groups were calculated by t-tests for dependent samples.
4. Results About half of all subjects were in pre-action stages (19% PC, 25% C, and 4% PR); about 11% were currently changing their behavior (A stage), while most subjects (41%) indicated that they had paid attention to their posture while performing activities of daily living for more than 6 months (M stage). There were no significant gender differences for stage distribution ( x 2 5 3.15, df 5 4, n 5 149, n.s.). The validity of the stage distribution was supported by the results for the use of preventive behaviors (see Table 2). The scores were significantly different between the stages (ANOVA; F(4,144) 5 27.15; P , 0.001; h 2 5 0.43). The large effect size indicates that these differences are substantial. As can be seen in Fig. 1, the use of preventive behaviors (expressed in standardized T scores; Mean 5 50, S.D. 5 10) increased almost linearly across the stages. Post hoc comparisons (Tukey, P , 0.05) showed that scores for subjects in PC and C were significantly lower than for subjects in the A and M stages; subjects in PR also scored lower than those in M. These results indicate that subjects in later stages more frequently use behaviors
Fig. 1. Means for self-efficacy and the use of preventive behaviors across the stages of change (transformed into T scores, Mean 5 50, S.D. 5 10). PC, precontemplation; C, contemplation; PR, preparation; A, action; M, maintenance.
which are assumed to be preventive for the development of back pain episodes. The differences in self-efficacy scores for maintaining an upright body posture between the five stages of change were highly significant; the effect size indicated a medium effect (F(4,138) 5 4.99; P , 0.001; h 2 5 0.13). The scores in Table 2 suggest that self-efficacy is higher in the action stages (A and M) than in the pre-action stages (PC, C, and PR). Due to differences in sub-sample sizes this assumption is only partially supported by the results of the post hoc comparison, where the scores for subjects in M were significantly higher than for subjects in PC
Table 2 Preventive behaviors, self-efficacy, and decisional balance across the stages of change a Stages of change b
Variable
Preventive behaviors Self-efficacy Pros Cons a
Mean S.D. Mean S.D. Mean S.D. Mean S.D.
PC (n 5 28)
C (n 5 37)
PR (n 5 6)
A (n 5 16)
M (n 5 62)
1.91 0.35 2.60 0.74 3.40 0.80 2.41 0.76
2.21 0.40 2.76 0.62 3.81 0.59 2.39 0.55
2.33 0.35 2.61 0.55 3.73 0.48 2.28 0.60
2.61 0.61 3.10 0.74 3.94 0.68 2.10 0.35
2.93 0.54 3.16 0.61 3.98 0.59 2.02 0.55
All scales range from 1 to 5. S.D., standard deviation. PC, precontemplation; C, contemplation; PR, preparation; A, action; M, maintenance. c Tukey, P , 0.05. b
ANOVA
Post hoc c
F(4,144) 5 27.15; P , 0.001; h 2 5 0.43 F(4,138) 5 4.99; P , 0.01; h 2 5 0.13 F(4,144) 5 4.14; P , 0.01; h 2 5 0.10 F(4,144) 5 3.41; P , 0.05; h 2 5 0.09
PC,C , A,M; PR , M PC, C , M PC , M PC, C . M
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and C. Thus, subjects in the M stage have a higher confidence that they can maintain an upright body posture across a variety of situations than subjects who have not considered taking action. Fig. 1 shows the standardized T scores for self-efficacy across the stages of change. The perceived pros of maintaining an upright posture also increased significantly across the stages of change (F(4,144) 5 4.14; P , 0.01; h 2 5 0.10). The effect is of a medium size; post hoc comparisons suggest higher pro scores for the subjects in the M stage than in the PC stage (see Table 2). The increase from PC to M is 8.7 T scores which is very close to the expected increase of about 1 S.D. ( 5 10 T scores). For the cons, the results were also in the expected direction: scores decreased across the stages by 6.4 T scores; the differences between the stages were statistically significant on a 5% error level with a medium effect size (F(4,144) 5 3.41; P , 0.05; h 2 5 0.09). Post hoc comparisons confirmed that the perceived cons were higher in PC and C than in M (Table 1). To facilitate comparisons with the pros and cons in other behavior areas, Fig. 2 shows the T scores (standardized Mean 5 50, S.D. 5 10) across the stages of change: the typical crossover between pros and cons can be observed between the PR and A stages. Subjects in the PC stage weighed the cons of keeping an upright posture significantly higher than the pros (t(df 5 27) 5 3.43, P , 0.01);
this was reversed in the M stage, where the pros were perceived as more important as the cons (t(df 5 61) 5 3.17, P , 0.01). The differences between pros and cons for the other stages were not significant. These results confirm the assumption that the stages of change for maintaining an upright body posture can be characterized by differences in the perceived pros and cons of this behavior. There were no gender differences for self-efficacy, pros, or cons; however, women showed preventive behaviors more frequently than men (women: Mean 5 2.75, S.D. 5 0.74; men: Mean 5 2.45, S.D. 5 0.66; t 5 2.61, P , 0.05). The subjects’ age correlated positively with their stage of change (r 5 0.23, P , 0.01), preventive behaviors (r 5 0.31, P , 0.01) and self-efficacy (r 5 0.20, P , 0.05), i.e., older individuals were more likely to be in a higher stage, show more preventive behavior, and have a higher self-efficacy. In the construction of the scales a considerable effort was made to avoid operational redundancies and repetitive items. Overall, the intercorrelations between the scales were in the expected directions but moderate. As could be expected, the highest correlation was found between self-efficacy and preventive behaviors (r 5 0.54; P , 0.01); all other correlations were r , 0.38. The cons correlated significantly only with self efficacy (r 5 2 0.23; P , 0.05).
5. Discussion
Fig. 2. Means for the pros and cons of maintaining an upright body posture across the stages of change (transformed into T scores, Mean 5 50, S.D. 5 10). PC, precontemplation; C, contemplation; PR, preparation; A, action; M, maintenance.
The aim of this study was to evaluate the applicability and validity of core constructs of the TTM for the target behavior ‘maintaining a biomechanically adequate body posture’. Based on the research summarized in the introduction, a mostly upright posture — together with regular exercise — can be considered an important aspect for the prevention of back pain episodes and pain chronicity. Since the long-term effectiveness of preventive interventions for back pain is not yet convincing, more knowledge about the adoption of prevention strategies is considered crucial. While the validity of the TTM has been confirmed for a broad variety of other (risk) behaviors, the readiness to keep a biomechanically adequate posture during the activities of daily living has not yet been
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assessed. We expected that subjects could be validly categorized into the stages of change for this behavior, that the cognitive variables self-efficacy and pros of change would increase, and that the cons of change would decrease across the stages of change. The measures we used to test our hypothesis were specific for the behavior in question. Their validity and reliability had been confirmed in previous studies [36]. All psychometric properties were good or satisfactory, although adding or exchanging items of the con-scale could probably increase the internal consistency. Most of our expectations regarding the TTM constructs were confirmed. The staging algorithm we used was sensitive enough to differentiate the readiness for behavior change in our subjects. The presentation of a behavioral definition for ‘keeping an upright posture’ may have contributed to the fact that all five stages were represented, although only few subjects (4%) were in the PR stage. This finding is not unusual; the reason is most probably that this is a transient stage, representing only the short time period of ‘the next 30 days’ and thus limiting the number of subjects being in it. About half of all subjects (11% A 1 41% M) indicated that they already showed the target behavior, i.e., an upright body posture most of the time. To evaluate the validity of the staging algorithm — and the stage distribution — we had included a self-report measure that assessed the frequency with which a number of preventive behaviors were shown. The scores increased almost linearly across the stages of change. Post-hoc comparisons confirmed that subjects who indicated that they were actively maintaining a good body posture (stages A and M) also had significantly higher scores, i.e., they showed a more favorable overall behavior regarding the health of their backs, than subjects in the PC and C stages. Additionally, subjects in M also had higher scores than subjects who were ready to change their behavior (stage PR). These results confirm the validity of the staging algorithm, which is an essential basis for the evaluation of the relation between the readiness to change and the other TTM constructs. These results also indicate that a more economical algorithm to assess the stage of change than the scale used by Kerns and colleagues for chronic pain patients [34,35] can lead to satisfactory results for a
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specified behavior like posture. However, future studies should also try to further validate the subjective staging with an external criterion like a videosupported behavior observation [23]. Subjects who overestimate their abilities and do not actually show the target behavior (yet) may otherwise be overlooked for a preventive intervention. Self-efficacy, i.e., the confidence that one can show the target behavior across a variety of situations, also increased significantly across the stages of change. As in other behavior areas, differences in self-efficacy between the stages are most obvious and statistically significant between pre-action and action stages. Post hoc comparisons could not confirm significant differences between the PR and A stages, but this may be attributed to the very small cell sizes for these groups. Overall, these results are consistent with those in other risk behaviors. Selfefficacy has been identified as a powerful predictor for behavior change in different behavior areas [30,31]. However, the cross-sectional design of our study does not allow a conclusion about the predictive value of self-efficacy for adopting an upright body posture. An increase in self-efficacy could be an important step towards behavior change, but might just as well be a result of it. Longitudinal data are essential to explain the relationship between self-efficacy and behavior change. Finally, the decisional balance variables related to the stages of change as expected from the TTM theory. The pros of the target behavior increased across the stages of change. Post-hoc comparisons confirmed a significant difference between the PC and M stage. The raw scores suggest that the pros increase from PC to C and then stay at a similar level across the other stages, but in order to confirm this assumption, larger sample sizes would be needed. Between the PC and M stage the difference expressed in standardized scores was 8.7 T points which is close to the 10 T points (1 S.D.) predicted by Prochaska [27] across various behaviors. The differences of the cons between the stages were smaller; con-scores decreased between PC and A by about 6.4 T points, again close to the difference proposed as a general rule by Prochaska. The raw scores suggest that the cons are on the same level in PC and C and then decline in the later stages. The profile of pros and cons across the stages, expressed
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in standardized scores, showed the typical crossover; the fact that it happened rather late (between PR and A instead of C and PR) may be attributed to the small number of subjects in the PR stage. Overall, these results can be seen as a confirmation of central assumptions of the TTM for the area of body posture. The stages of change are an organizing construct to which the construct of decisional balance relates in a replicable way. Subjects in preaction stages are characterized by weighing the cons of behavior change significantly higher than the pros. With taking action, the difference between pros and cons reverses, i.e., subjects who show the respective behavior weigh the pros as more important than the cons. Overall, the results are congruent with those of TTM applications in other behavior areas. However, some limitations of this study should be taken into account. One limitation is the nature of the sample: first of all, the sample size is comparatively small to evaluate the distribution across the stages and the relationship between stages and cognitive variables. The most important studies in other behavior areas by Prochaska and colleagues had sample sizes of more than 4000 subjects, allowing a more explicit micro-level analysis. Secondly, we looked at a worksite sample with hardly any recent pain experience. While this allows the assumption that the reported results are significant for early or primary prevention, a replication of the findings for clinical samples with pain experience is necessary in order to determine if the motivational mechanisms are different for subjects with and without pain experience. This information is especially important for tailoring interventions for primary, secondary, or tertiary prevention. For subjects with chronic pain, additional constructs like depression or fear of movement / (re)injury [38] may be moderating variables for the motivation to keep a certain posture or exercise regularly. Thus, studies with larger, representative samples as well as with clinical samples should be conducted in the future. A second limitation lies in the measures we used. Although all results are in the expected direction, this study can only be seen as the first step towards developing the necessary instruments for TTM-based interventions. First of all, another important construct of the TTM, the processes of change, has not been
operationalized yet and needs to be included in future studies. Secondly, further validation of the newly developed scales with external criteria, like a behavioral observation, should be performed. Our group has developed the necessary methodology [3,23], and a study to validate the self-report constructs with behavioral observation methods is in preparation. Finally, one limitation that applies to all back school-related studies also applies to ours: although our understanding of the back’s biomechanics provides a plausible basis for the assumption that certain postural habits and physical training lead to a lower incidence of back pain episodes or chronic back pain syndromes, longitudinal studies have yet to be conducted that empirically confirm this relationship. As summarized in Section 1, previous studies have come to contradictory results. Our results, however, suggest that assessing the moderating and mediating effects of motivational variables should be a part of such studies. Similar conclusions have been drawn for chronic pain patients by Kerns and Rosenberg [35]. The TTM provides a strong theoretical base for the behavior change motivation and our study introduces its application to postural behavior. As we pointed out earlier, maintaining an adequate body posture is most likely only one of several relevant behaviors for back pain prevention. While this study focussed on the applicability of the TTM to postural behavior, future studies should also include the assessment of other relevant behaviors, such as exercise or stress management. TTM-based operationalizations also exist for these behavior areas and a simultaneous assessment in longitudinal studies could contribute to a better understanding of the relevance and mediating effects of these behaviors for back pain prevention. Further research should also consider possible interactions between behaviors, e.g., between the ability to habitually keep a certain body posture and physical exercise. We expect that the conceptualization of the relevant target behaviors through core constructs of the TTM will enable us to further improve interventions, especially for primary and secondary back pain prevention, where pain frequency and intensity may not be an appropriate measure of success. By assessing subjects’ stages of change and cognitive variables for posture, exercise, and stress / pain manage-
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ment, individualized interventions can be offered which most probably lead to better long-term results in terms of behavior change and, hopefully, low back pain incidence. Encouraging individuals to start with changing their postural behavior before changing more complex behaviors may have some advantages: correcting one’s body posture, unlike regular exercise or using stress management techniques, requires little effort and time. Therefore, it may be more acceptable and easier to maintain as a preventive strategy. The results of this study indicate that people are in different stages of readiness to adopt this behavior. Education approaches should recognize these differences and tailor interventions toward the respective stages.
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[12] Wilke HJ, Neef P, Caimi M, Hoogland T, Claes LE. New in vivo measurements of pressures in the intervertebral disc in daily life. Spine 1999;24:755–62. [13] Basler HD, Keller S, Herda C. Good postural habits: a pilot investigation using EMG scanning of the paraspinals. Appl Psychophysiol Biofeedback 1997;22:171–82. [14] Biering-Sørensen F, Bendix T, Jørgensen K, Manniche C, Nielsen H. Physical activity, fitness and back pain. In: Bouchard C et al., editor, Physical activity, fitness and health: proceedings and consensus statement, Champaign, IL: Human Kinetics, 1994, pp. 737–48. [15] Harreby M, Hesselsoe G, Kjer J, Neergard K. Low back pain and physical exercise in leisure time in 38-year-old men and women: a 25-year prospective cohort study of 640 school children. Eur Spine J 1997;6:181–6. ¨ [16] Brugger A. Die Erkrankungen des Bewegungsapparates und ¨ ¨ seines Nervensystems, Zurich: Verlag Brugger, 1980. [17] Nordin M, Cedraschi C, Balague´ F, Roux EB. Back schools in prevention of chronicity. Bailliere Clin Rheumatol 1992;6:685–703. [18] Koes BW, van Tulder MW, van der Windt WM, Bouter LM. The efficacy of back schools: a review of randomized clinical trials. J Clin Epidemiol 1994;47:851–62. [19] DiFabio RP. Efficacy of comprehensive rehabilitation programs and back school for patients with low back pain: a meta-analysis. Phys Ther 1995;75:865–78. ¨ ¨ von Ruck¨ [20] Maier-Riehle B, Harter M. Die Effektivitat enschulen aus empirischer Sicht — Eine Metaanalyse. Z Gesundheitspsychol 1996;4:197–219. [21] Dishman RK. Exercise adherence research: future directions. Am J Health Prom 1988;3:52–6. [22] Robison JI, Rogers MA. Adherence to exercise programmes: recommendations. Sports Med 1994;17:39–52. ¨ [23] Keller S, Bauer B, Herda C, Marx O, Kuster T, Basler HD. ¨ Auswirkungen einer Ruckenschule auf Befinden, Verhalten, ¨ — Ergebnisse einer konEinstellungen und Muskelaktiviat trollierten Studie. Z Gesundheitspsychol 1996;4:179–96. [24] Prochaska JO, Redding C, Evers K. The Transtheoretical Model of behavior change. In: Glanz K, Lewis FM, Rimer BK, editors, Health behavior and health education: theory, research and practice, San Francisco, CA: Jossey-Bass Publications, 1996, pp. 60–84. [25] Prochaska JO, Velicer WF. The transtheoretical model of behavior change. Am J Health Prom 1997;12:38–48. [26] Janis IL, Mann L. In: Decision making: a psychological analysis of conflict, chance, and commitment, London: Cassil and Collier Macmillen, 1977. [27] Prochaska JO. Strong and weak principles for progressing from precontemplation to action on the basis of twelve problem behaviors. Health Psychol 1994;13:47–51. [28] Prochaska JO, Velicer WF, Rossi JS, Goldstein MG, Marcus BH, Rakowski W, Fiore C, Harlow LL, Redding CA, Rosenbloom D, Rossi SS. Stages of change and decisional balance for 12 problem behaviors. Health Psychol 1994;13:39–46. [29] Bandura A. Self-efficacy mechanism in human agency. Am Psychol 1982;37:122–47.
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[30] Velicer WF, DiClemente CC, Rossi JS, Prochaska JO. Relapse situations and self-efficacy: an integrative model. Addict Behav 1990;15:271–83. [31] Marcus BH, Eaton CA, Rossi JS, Harlow LL. Self-efficacy, decision making, and stages of change: an integrative model of physical exercise. J Appl Soc Psychol 1994;24:489–508. [32] Marcus BH, Pinto BM, Forsyth LH, Roberts MB, Traficante RM. Efficacy of an individualized, motivationally-tailored physical activity intervention. Ann Behav Med 1988;20:174– 80. [33] Nigg CR, Courneya KS. Transtheoretical Model: examining adolescent exercise behavior. J Adolesc Health 1998;22:214–24. [34] Kerns RD, Rosenberg R, Jamison RN, Caudill MA, Haythornthwaite J. Readiness to adopt a self-management approach to chronic pain: the pain stages of change questionnaire (PSOCQ). Pain 1997;72:227–34.
[35] Kerns RD, Rosenberg R. Predicting responses to self-management treatments for chronic pain: application of the pain stages of change model. Pain 2000;84:49–55. [36] Basler HD, Keller S, Herda C, Ridder K. Selbstwirksamkeit¨ serwartung, Entscheidungsbalance und ruckenbewußtes Ver¨ ¨ halten zur Pravention von Ruckenschmerz — eine Studie zum Transtheoretischen Modell. Z Med Psychol 1998;4:149–57. [37] Marcus BH, Rakowski W, Rossi JS. Assessing motivational readiness and decision making for exercise. Health Psychol 1992;11:257–61. [38] Vlaeyen JW, Kole-Snijders AM, Boeren RG, van Eek H. Fear of movement /(re)injury in chronic low back pain and its relation to behavioral performance. Pain 1995;62:363–72.
Readiness to adopt adequate postural habits: an application of the Transtheoretical Model in the context of back pain prevention Stefan Keller a
a,b ,
*, Christoph Herda a , Kai Ridder a , Heinz-Dieter Basler a
Institute for Medical Psychology, University of Marburg, Bunsenstr. 3, 35033 Marburg, Germany b Cancer Prevention Research Center, University of Rhode Island, Rhode Island, USA Received 30 July 1999; received in revised form 15 February 2000; accepted 24 February 2000
Abstract Based on a biomechanical model, an adequate body posture can contribute to the prevention of back pain and back pain chronicity. This study examines the explanatory value of the Transtheoretical Model (TTM) for the adoption of adequate postural habits in a cross-sectional sample of 149 employees of a German administration unit (mean age 40.2 years, 50% female). Using newly developed instruments with satisfactory psychometric properties, basic assumptions of the TTM could be confirmed: self-efficacy and the perceived pros for maintaining a good body posture increased significantly across the stages, while the perceived cons decreased. Additionally, the use of preventive strategies for back pain prevention increased linearly and significantly across the stages of change. The study supports the applicability of the TTM for postural behavior. Considering stages of change as an intervening variable may contribute to clarifying the relationship between participation in low back schools and prevention of back pain chronicity. Longitudinal and intervention study data are needed to support these assumptions. 2001 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Prevention; Posture; Transtheoretical Model; Behavior change
1. Introduction Comprehensive treatment approaches incorporating behavioral, biomedical, psychological, physical, and social components have proven to be most effective in the treatment of chronic pain [1]. Recently, more attention was given to mechanisms that lead from highly prevalent single pain episodes to chronic *Corresponding author. Tel.: 1 49-6421-286-3774; fax: 1 496421-286-4881. E-mail address: [email protected] (S. Keller).
0738-3991 / 01 / $ – see front matter PII: S0738-3991( 00 )00103-8
pain syndromes. Basler [2] describes four factors contributing to pain chronicity: biomechanical stress, psychosocial stress, operant conditioning mechanisms, and dysphoric mood. Consequently, physical exercise, training of posture and activities of daily living, and stress / pain management are seen as crucial intervention modules for the prevention of chronicity [3]. As Turk and Okifuji [4] pointed out, in the process of chronicity psychological and behavioral factors mainly help maintain and exacerbate pain, disability, and psychological distress, whereas biomechanical factors are more relevant to the
2001 Elsevier Science Ireland Ltd. All rights reserved.
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acquisition of pain. This paper will focus on the motivation to adopt behavior relevant to the biomechanical risk factors for pain chronicity. Biomechanical stress of the back can be caused by heavy work like lifting, long-term exposure to vibration, or sedentary or monotonous job functions [5–8]. The biomechanical model of chronic pain assumes a relationship between external strain, body posture, muscle activity, and intravertebral pressure [9]. According to this model, chronic pain is a result of an abnormal pattern of paraspinal activity caused by overexertion and poor postural habits. It is believed that such irregular muscle activity provides abnormal support for the spine, which in turn becomes unstable. The instability of the spine enhances the possibility of impingement upon nerve endings and abnormal pressure on the discs, and thereby produces pain [10]. Support for this model dates back to early studies conducted by Nachemson and co-workers. By means of intradiscular and electromyographic (EMG) measurements, these authors were able to demonstrate that the pressure exerted on lumbar discs as well as the activity of the paraspinal muscles are determined by the position of the spine [10,11]. Recent research has generally confirmed these results [12,13]. An additional risk factor is physical inactivity: it can lead to muscular deconditioning and a loss of muscle strength and to an increased risk for the development of low back pain complaints [14,15]. One way to lower the impact of biomechanical stress is to keep an adequate body posture while performing activities of daily living. Based on the works of Nachemson and colleagues and the Swiss ¨ neurologist Brugger [16] such a ‘physiological posture’ can be conceptualized as consisting of a pronounced lumbar lordosis, an erected thorax with a thoracic kyphosis, and a stretching of the cervical spine. With regard to the overall distribution of pressure in the spinal structures, a pronounced rotation of the pelvis is expected to be most beneficial. In a sitting position, the center of gravity is moved forwards and is located slightly above and ventral from the ischial tuberosities. The findings regarding the importance of biomechanical stress serve as a basis for numerous back school programs which usually follow two principles: education and encouragement to improve body posture as well as to perform an exercise program on
a regular basis. Additional treatment modules may be added, depending on the target group and the intervention setting [17]. However, the empirical evidence for the effectiveness of back schools is not convincing. Attempts to analyze the efficacy of back schools are complicated by the limited methodological quality of some of the original studies [18]. Meta-analyses suggest that, for patients with acute or chronic back pain, back schools show hardly any impact [18], especially when they are offered as a ¨ sole treatment [19]. Maier-Riehle and Harter [20] conclude from their meta-analysis based on 18 controlled studies that positive short-term results can be observed especially for knowledge and backfriendly behavior, but the results are not favorable for clinical variables (e.g., pain intensity) or health economic variables (e.g., utilization of health care services). For the time points more than 6 months after the intervention no positive effect for any of 14 dependent variables could be confirmed. A possible explanation for these findings may be that not enough attention has been paid to the intervening variables: the frequency and intensity of pain episodes and other variables may only be affected if the target behaviors of a back school intervention — adequate body posture and regular physical exercise — are adopted habitually and continuously. To date, little is known about the stability of changes in these behaviors during back school programs or the follow-up periods. Experiences from exercise research show that in spite of the positive effects, 50% of all subjects who begin to exercise will discontinue after 3–6 months [21,22]. With regard to body posture, we could document with a video-supported behavior observation method that participants of preventive back school programs learned to perform a variety of activities of daily living adequately [3,23]. However, the majority of all subjects admitted at the 1-year follow-up that they considerably decreased the frequency and intensity of physical exercises and the awareness towards their body posture [23].
2. The Transtheoretical Model (TTM) Considering these findings, stronger efforts should be made to integrate research for back pain prevention with research about models and methods of
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behavior change. One model that has produced promising results in this context is TTM (also ‘Stages of Change Model’) developed by Prochaska and colleagues [24,25]. The TTM is based on the premise that people move through a series of stages in their attempt to change a behavior. Five stages of change have been reliably identified across health behaviors: precontemplation (PC, no intention to change behavior in the foreseeable future, or denial of need to change); contemplation (C, intention to change within the next 6 months); preparation (PR, serious intention to change in the next 30 days); action (A, initiation of overt behavioral change); and maintenance (M, sustaining behavioral change for 6 months or more). Movement through these stages may not occur in a linear fashion; often individuals move through the stages repeatedly in a cyclical manner before maintenance is reached. The TTM proposes integration of the stages of change with the processes of change, self-efficacy, and decisional balance. The stages represent an organizing structure and a temporal dimension describing when cognitive and behavioral changes occur. The processes of change describe how these shifts occur and are divided into experiential and behavioral processes. Decisional balance focuses on the perceived benefits (pros) and costs (cons) of a behavior, and is important in decision making [26]. The pros and cons are relevant in understanding and predicting transitions between the PC, C, and PR stage. Cons always outweigh the pros of changing a behavior in the PC stage and the opposite is true for the A and M stages. Between the C and PR stages, pros and cons usually intersect [27,28]. Finally, selfefficacy involves one’s confidence that one can perform a behavior required to achieve a certain outcome across a variety of situations. It is also believed to be a critical construct in behavior change [29]. Self-efficacy increases across the stages of change and is an important predictor of stage, especially at the A and M stages [30]. The TTM has been successfully applied to numerous health risk behaviors like smoking cessation, dietary fat consumption, ultraviolet light exposure, alcohol abuse, screening mammography, and others [24,28]. Recent research has also confirmed the validity of the TTM for the adoption of regular exercise [31–33]. The baseline stage of change was found to be a predictor of future exercise behavior;
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self-efficacy increased linearly across the stages; the pros of exercise also increased while the cons decreased between PC and A. While first promising steps have been undertaken to assess the readiness of chronic pain patients to use self-management strategies [34,35], no study has yet focused on the readiness to perform activities of daily living with a body posture that is adequate for the prevention of back pain. The aim of this study is to evaluate the applicability and the validity of core constructs of the TTM for adopting and maintaining an upright body posture during activities of daily living. Based on the findings in other areas, especially for exercise behavior, we expect that subjects can be validly categorized in five stages of change, and that self-efficacy and the perceived pros of good postural behavior increase across the stages while the cons decrease. This implies that the cons are higher than the pros in the PC and lower in the M stages.
3. Methods
3.1. Sample The sample consisted of employees of a large administrative unit (unemployment office) in Germany. All of them were working in offices, predominantly in a sitting position most of the day. Of 180 distributed questionnaires, 149 were returned (response rate 83%). The mean age of the respondents was 40.2 years (S.D. 5 12.3), 50% were females. The level of education was somewhat above the population average, 20% had a university degree; almost all subjects lived with a partner (83%). About 83% indicated that they had ‘never’ or ‘seldom’ experienced back pain in the 2 weeks previous to the assessment.
3.2. Measures 3.2.1. Staging algorithm for maintaining an upright body posture Subjects were staged by the algorithm shown in Table 1. To ensure that all subjects had a comparable concept of a ‘physiological posture’ a short and easy-to-understand definition was presented before the staging questions. Subjects were categorized into the five stages of change (see Table 1). Although the
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Table 1 Staging algorithm for maintaining an upright body posture a For the prevention of back problems it is important to continuously engage in preventive behaviors, not only in certain situations but also in during activities of daily living and leisure time activities. This means, for example, maintaining an upright body posture while sitting or bending your knees when lifting objects from the floor. 1. Do you engage in behaviors to prevent back problems most of the time, i.e., do you consciously maintain an upright body posture? (1) No, and I do not intend to change my behavior. (2) No, but I intend to change my behavior in the next 6 months. (3) No, but I intend to change my behavior in the next 30 days. (4) Yes, I have kept a good body posture, but for less than 6 months. (5) Yes, I have kept a good body posture for more than 6 months. 2. In the last 6 month, have you made any steps to actively deal with the topic of good body posture, like reading a book or watching a TV program about it? Yes No a Scoring: Subjects are categorized into the stages precontemplation (answer (1)), contemplation (2), action (4) or maintenance (5) based on the answers to question 1. Subjects who stage themselves as being in preparation (3) are re-staged into contemplation unless they have already made an attempt to change their behavior according to question 2.
staging algorithm is comparatively short, its usefulness and validity had been confirmed across a variety of other behaviors [25].
3.2.2. Preventive behaviors A scale had been developed in previous studies describing the utilization of behaviors that are considered preventive for the development of back pain. The core of the scale was built by items that had shown to be valid in the context of a controlled back school intervention study with video-based behavior observation [3,23]. Sample items are ‘‘In the previous 2 weeks, I interrupted long sedentary activities and moved for a few minutes.’’ or ‘‘In the previous 2 weeks, I made sure to keep my back straight when vacuuming.’’. Ratings were made on a 5-point Likert scale, ranging from 1 5 ‘never’ to 5 5 ‘always’. The revised 26-item scale had a one-factorial structure explaining 33% of the variance and good psychometric properties (a 5 0.91) [36]. 3.2.3. Self-efficacy On a scale ranging from 1 5 ‘not confident’ to 5 5 ‘extremely confident’, subjects were asked to rate their confidence that they could keep the defined body posture in a variety of situations. The situations included behavioral and cognitive-emotional aspects.
Sample items are: ‘‘How confident are you that you keep an upright body posture when you are sitting at your desk?’’ or ‘‘How confident are you that you show an upright body posture when you are down and depressed?’’. The 20-item scale had a onefactorial structure explaining 30% of the variance and good psychometric properties (a 5 0.92) [36].
3.2.4. Decisional balance The scales to measure pros and cons of keeping the defined body posture most of the time were adapted from a decisional balance measure for exercise described by Marcus et al. [37]. Eleven items describe the pros of the respective behavior (example: ‘‘If I keep an upright body posture I can prevent backpain.’’), and six items the cons (example: ‘‘If I keep an upright body posture I will appear to be arrogant.’’). Subjects rated how important each of these statements is for their decision to show the target behavior. The psychometric properties were good for the pros (a 5 0.89) and satisfactory for the cons (a 5 0.66) [36]. 3.3. Statistical analysis For description purposes, means, standard deviations, and percentages were computed. To account
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for group differences, one-way analysis of variance was used. Follow-up tests were conducted by Tukey’s procedure. Comparisons within groups were calculated by t-tests for dependent samples.
4. Results About half of all subjects were in pre-action stages (19% PC, 25% C, and 4% PR); about 11% were currently changing their behavior (A stage), while most subjects (41%) indicated that they had paid attention to their posture while performing activities of daily living for more than 6 months (M stage). There were no significant gender differences for stage distribution ( x 2 5 3.15, df 5 4, n 5 149, n.s.). The validity of the stage distribution was supported by the results for the use of preventive behaviors (see Table 2). The scores were significantly different between the stages (ANOVA; F(4,144) 5 27.15; P , 0.001; h 2 5 0.43). The large effect size indicates that these differences are substantial. As can be seen in Fig. 1, the use of preventive behaviors (expressed in standardized T scores; Mean 5 50, S.D. 5 10) increased almost linearly across the stages. Post hoc comparisons (Tukey, P , 0.05) showed that scores for subjects in PC and C were significantly lower than for subjects in the A and M stages; subjects in PR also scored lower than those in M. These results indicate that subjects in later stages more frequently use behaviors
Fig. 1. Means for self-efficacy and the use of preventive behaviors across the stages of change (transformed into T scores, Mean 5 50, S.D. 5 10). PC, precontemplation; C, contemplation; PR, preparation; A, action; M, maintenance.
which are assumed to be preventive for the development of back pain episodes. The differences in self-efficacy scores for maintaining an upright body posture between the five stages of change were highly significant; the effect size indicated a medium effect (F(4,138) 5 4.99; P , 0.001; h 2 5 0.13). The scores in Table 2 suggest that self-efficacy is higher in the action stages (A and M) than in the pre-action stages (PC, C, and PR). Due to differences in sub-sample sizes this assumption is only partially supported by the results of the post hoc comparison, where the scores for subjects in M were significantly higher than for subjects in PC
Table 2 Preventive behaviors, self-efficacy, and decisional balance across the stages of change a Stages of change b
Variable
Preventive behaviors Self-efficacy Pros Cons a
Mean S.D. Mean S.D. Mean S.D. Mean S.D.
PC (n 5 28)
C (n 5 37)
PR (n 5 6)
A (n 5 16)
M (n 5 62)
1.91 0.35 2.60 0.74 3.40 0.80 2.41 0.76
2.21 0.40 2.76 0.62 3.81 0.59 2.39 0.55
2.33 0.35 2.61 0.55 3.73 0.48 2.28 0.60
2.61 0.61 3.10 0.74 3.94 0.68 2.10 0.35
2.93 0.54 3.16 0.61 3.98 0.59 2.02 0.55
All scales range from 1 to 5. S.D., standard deviation. PC, precontemplation; C, contemplation; PR, preparation; A, action; M, maintenance. c Tukey, P , 0.05. b
ANOVA
Post hoc c
F(4,144) 5 27.15; P , 0.001; h 2 5 0.43 F(4,138) 5 4.99; P , 0.01; h 2 5 0.13 F(4,144) 5 4.14; P , 0.01; h 2 5 0.10 F(4,144) 5 3.41; P , 0.05; h 2 5 0.09
PC,C , A,M; PR , M PC, C , M PC , M PC, C . M
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and C. Thus, subjects in the M stage have a higher confidence that they can maintain an upright body posture across a variety of situations than subjects who have not considered taking action. Fig. 1 shows the standardized T scores for self-efficacy across the stages of change. The perceived pros of maintaining an upright posture also increased significantly across the stages of change (F(4,144) 5 4.14; P , 0.01; h 2 5 0.10). The effect is of a medium size; post hoc comparisons suggest higher pro scores for the subjects in the M stage than in the PC stage (see Table 2). The increase from PC to M is 8.7 T scores which is very close to the expected increase of about 1 S.D. ( 5 10 T scores). For the cons, the results were also in the expected direction: scores decreased across the stages by 6.4 T scores; the differences between the stages were statistically significant on a 5% error level with a medium effect size (F(4,144) 5 3.41; P , 0.05; h 2 5 0.09). Post hoc comparisons confirmed that the perceived cons were higher in PC and C than in M (Table 1). To facilitate comparisons with the pros and cons in other behavior areas, Fig. 2 shows the T scores (standardized Mean 5 50, S.D. 5 10) across the stages of change: the typical crossover between pros and cons can be observed between the PR and A stages. Subjects in the PC stage weighed the cons of keeping an upright posture significantly higher than the pros (t(df 5 27) 5 3.43, P , 0.01);
this was reversed in the M stage, where the pros were perceived as more important as the cons (t(df 5 61) 5 3.17, P , 0.01). The differences between pros and cons for the other stages were not significant. These results confirm the assumption that the stages of change for maintaining an upright body posture can be characterized by differences in the perceived pros and cons of this behavior. There were no gender differences for self-efficacy, pros, or cons; however, women showed preventive behaviors more frequently than men (women: Mean 5 2.75, S.D. 5 0.74; men: Mean 5 2.45, S.D. 5 0.66; t 5 2.61, P , 0.05). The subjects’ age correlated positively with their stage of change (r 5 0.23, P , 0.01), preventive behaviors (r 5 0.31, P , 0.01) and self-efficacy (r 5 0.20, P , 0.05), i.e., older individuals were more likely to be in a higher stage, show more preventive behavior, and have a higher self-efficacy. In the construction of the scales a considerable effort was made to avoid operational redundancies and repetitive items. Overall, the intercorrelations between the scales were in the expected directions but moderate. As could be expected, the highest correlation was found between self-efficacy and preventive behaviors (r 5 0.54; P , 0.01); all other correlations were r , 0.38. The cons correlated significantly only with self efficacy (r 5 2 0.23; P , 0.05).
5. Discussion
Fig. 2. Means for the pros and cons of maintaining an upright body posture across the stages of change (transformed into T scores, Mean 5 50, S.D. 5 10). PC, precontemplation; C, contemplation; PR, preparation; A, action; M, maintenance.
The aim of this study was to evaluate the applicability and validity of core constructs of the TTM for the target behavior ‘maintaining a biomechanically adequate body posture’. Based on the research summarized in the introduction, a mostly upright posture — together with regular exercise — can be considered an important aspect for the prevention of back pain episodes and pain chronicity. Since the long-term effectiveness of preventive interventions for back pain is not yet convincing, more knowledge about the adoption of prevention strategies is considered crucial. While the validity of the TTM has been confirmed for a broad variety of other (risk) behaviors, the readiness to keep a biomechanically adequate posture during the activities of daily living has not yet been
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assessed. We expected that subjects could be validly categorized into the stages of change for this behavior, that the cognitive variables self-efficacy and pros of change would increase, and that the cons of change would decrease across the stages of change. The measures we used to test our hypothesis were specific for the behavior in question. Their validity and reliability had been confirmed in previous studies [36]. All psychometric properties were good or satisfactory, although adding or exchanging items of the con-scale could probably increase the internal consistency. Most of our expectations regarding the TTM constructs were confirmed. The staging algorithm we used was sensitive enough to differentiate the readiness for behavior change in our subjects. The presentation of a behavioral definition for ‘keeping an upright posture’ may have contributed to the fact that all five stages were represented, although only few subjects (4%) were in the PR stage. This finding is not unusual; the reason is most probably that this is a transient stage, representing only the short time period of ‘the next 30 days’ and thus limiting the number of subjects being in it. About half of all subjects (11% A 1 41% M) indicated that they already showed the target behavior, i.e., an upright body posture most of the time. To evaluate the validity of the staging algorithm — and the stage distribution — we had included a self-report measure that assessed the frequency with which a number of preventive behaviors were shown. The scores increased almost linearly across the stages of change. Post-hoc comparisons confirmed that subjects who indicated that they were actively maintaining a good body posture (stages A and M) also had significantly higher scores, i.e., they showed a more favorable overall behavior regarding the health of their backs, than subjects in the PC and C stages. Additionally, subjects in M also had higher scores than subjects who were ready to change their behavior (stage PR). These results confirm the validity of the staging algorithm, which is an essential basis for the evaluation of the relation between the readiness to change and the other TTM constructs. These results also indicate that a more economical algorithm to assess the stage of change than the scale used by Kerns and colleagues for chronic pain patients [34,35] can lead to satisfactory results for a
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specified behavior like posture. However, future studies should also try to further validate the subjective staging with an external criterion like a videosupported behavior observation [23]. Subjects who overestimate their abilities and do not actually show the target behavior (yet) may otherwise be overlooked for a preventive intervention. Self-efficacy, i.e., the confidence that one can show the target behavior across a variety of situations, also increased significantly across the stages of change. As in other behavior areas, differences in self-efficacy between the stages are most obvious and statistically significant between pre-action and action stages. Post hoc comparisons could not confirm significant differences between the PR and A stages, but this may be attributed to the very small cell sizes for these groups. Overall, these results are consistent with those in other risk behaviors. Selfefficacy has been identified as a powerful predictor for behavior change in different behavior areas [30,31]. However, the cross-sectional design of our study does not allow a conclusion about the predictive value of self-efficacy for adopting an upright body posture. An increase in self-efficacy could be an important step towards behavior change, but might just as well be a result of it. Longitudinal data are essential to explain the relationship between self-efficacy and behavior change. Finally, the decisional balance variables related to the stages of change as expected from the TTM theory. The pros of the target behavior increased across the stages of change. Post-hoc comparisons confirmed a significant difference between the PC and M stage. The raw scores suggest that the pros increase from PC to C and then stay at a similar level across the other stages, but in order to confirm this assumption, larger sample sizes would be needed. Between the PC and M stage the difference expressed in standardized scores was 8.7 T points which is close to the 10 T points (1 S.D.) predicted by Prochaska [27] across various behaviors. The differences of the cons between the stages were smaller; con-scores decreased between PC and A by about 6.4 T points, again close to the difference proposed as a general rule by Prochaska. The raw scores suggest that the cons are on the same level in PC and C and then decline in the later stages. The profile of pros and cons across the stages, expressed
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in standardized scores, showed the typical crossover; the fact that it happened rather late (between PR and A instead of C and PR) may be attributed to the small number of subjects in the PR stage. Overall, these results can be seen as a confirmation of central assumptions of the TTM for the area of body posture. The stages of change are an organizing construct to which the construct of decisional balance relates in a replicable way. Subjects in preaction stages are characterized by weighing the cons of behavior change significantly higher than the pros. With taking action, the difference between pros and cons reverses, i.e., subjects who show the respective behavior weigh the pros as more important than the cons. Overall, the results are congruent with those of TTM applications in other behavior areas. However, some limitations of this study should be taken into account. One limitation is the nature of the sample: first of all, the sample size is comparatively small to evaluate the distribution across the stages and the relationship between stages and cognitive variables. The most important studies in other behavior areas by Prochaska and colleagues had sample sizes of more than 4000 subjects, allowing a more explicit micro-level analysis. Secondly, we looked at a worksite sample with hardly any recent pain experience. While this allows the assumption that the reported results are significant for early or primary prevention, a replication of the findings for clinical samples with pain experience is necessary in order to determine if the motivational mechanisms are different for subjects with and without pain experience. This information is especially important for tailoring interventions for primary, secondary, or tertiary prevention. For subjects with chronic pain, additional constructs like depression or fear of movement / (re)injury [38] may be moderating variables for the motivation to keep a certain posture or exercise regularly. Thus, studies with larger, representative samples as well as with clinical samples should be conducted in the future. A second limitation lies in the measures we used. Although all results are in the expected direction, this study can only be seen as the first step towards developing the necessary instruments for TTM-based interventions. First of all, another important construct of the TTM, the processes of change, has not been
operationalized yet and needs to be included in future studies. Secondly, further validation of the newly developed scales with external criteria, like a behavioral observation, should be performed. Our group has developed the necessary methodology [3,23], and a study to validate the self-report constructs with behavioral observation methods is in preparation. Finally, one limitation that applies to all back school-related studies also applies to ours: although our understanding of the back’s biomechanics provides a plausible basis for the assumption that certain postural habits and physical training lead to a lower incidence of back pain episodes or chronic back pain syndromes, longitudinal studies have yet to be conducted that empirically confirm this relationship. As summarized in Section 1, previous studies have come to contradictory results. Our results, however, suggest that assessing the moderating and mediating effects of motivational variables should be a part of such studies. Similar conclusions have been drawn for chronic pain patients by Kerns and Rosenberg [35]. The TTM provides a strong theoretical base for the behavior change motivation and our study introduces its application to postural behavior. As we pointed out earlier, maintaining an adequate body posture is most likely only one of several relevant behaviors for back pain prevention. While this study focussed on the applicability of the TTM to postural behavior, future studies should also include the assessment of other relevant behaviors, such as exercise or stress management. TTM-based operationalizations also exist for these behavior areas and a simultaneous assessment in longitudinal studies could contribute to a better understanding of the relevance and mediating effects of these behaviors for back pain prevention. Further research should also consider possible interactions between behaviors, e.g., between the ability to habitually keep a certain body posture and physical exercise. We expect that the conceptualization of the relevant target behaviors through core constructs of the TTM will enable us to further improve interventions, especially for primary and secondary back pain prevention, where pain frequency and intensity may not be an appropriate measure of success. By assessing subjects’ stages of change and cognitive variables for posture, exercise, and stress / pain manage-
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ment, individualized interventions can be offered which most probably lead to better long-term results in terms of behavior change and, hopefully, low back pain incidence. Encouraging individuals to start with changing their postural behavior before changing more complex behaviors may have some advantages: correcting one’s body posture, unlike regular exercise or using stress management techniques, requires little effort and time. Therefore, it may be more acceptable and easier to maintain as a preventive strategy. The results of this study indicate that people are in different stages of readiness to adopt this behavior. Education approaches should recognize these differences and tailor interventions toward the respective stages.
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