Health Education Research Advance Access published online on October 16, 2008
Health Education Research, doi:10.1093/her/cyn045
Determinants of awareness, initiation and maintenance of physical activity among the over-fifties: a Delphi study
1 Department of Psychology, Open University of the Netherlands, PO Box 2960, 6401 DL, Heerlen, the Netherlands
2 Department of Health Promotion and Health Education, University of Maastricht, PO Box 616, 6200 MD, Maastricht, the Netherlands
Correspondence to: * Correspondence to: M. M. van Stralen; E-mail: maartje.vanstralen{at}ou.nl
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Abstract |
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To develop effective interventions to stimulate physical activity (PA), insight into its underlying variables is needed. The aim of this study was to obtain an overview of the most relevant determinants of awareness, initiation and maintenance of PA among the over-fifties by means of a three-round Delphi study. In the first round, 17 key-experts outlined possible relevant determinants into an open-ended electronic questionnaire. In the second round, 118 experts completed a structured electronic questionnaire that was based on the first round results, in which they scored each determinant on its relevance. In the third round, experts were asked to re-rate the relevance of each determinant, after feedback was given about the group median relevance score. After three rounds, the experts agreed on 30 relevant determinants of the three phases of PA. When compared with longitudinal studies, the Delphi study pointed out new concepts, such as several post-motivational and social and environmental determinants as possible relevant determinants, suggesting that this method has the potential to trace new and promising determinants. The results further showed that next to similarities, much dissimilarity in relevant determinants of awareness, initiation and maintenance of PA was found, suggesting that most determinants could be phase specific.
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Introduction |
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Regular physical activity (PA) reduces the risks of health problems such as cardiovascular diseases, obesity and type-2 diabetes [1–7]. Moreover, all these disorders become more prevalent and their impact increases when people age [1]. Further, regular PA is particularly important for older adults to maintain their mobility [8] and independent living [9], for the improvement of muscle strength [10] mental and emotional well-being [11] and to prevent falls [12]. Together with the fact that older adults form a large percentage of the population; in the Netherlands, 32% of all residents are over 50 years of age [13], a percentage that will raise even further in the coming years [14, 15], stimulating PA among this large and growing group is of major relevance.
Despite PA is demonstrated to be important for health promotion and physical functioning among aging people, adults over the age of 50 represent the most sedentary segment of the adult population [1, 4, 13, 16]. Currently in the Netherlands, only 58.6% of the general population complies with the (inter)national health guideline [13, 16], which recommends people to be moderately physically active at least 5 days a week for a minimum of 30 min a day [4]. The amount of older adults complying to this guideline is even lower [13, 16], declining to <50% of adults aged 75 and over that complies with the guideline [16]. It can be concluded that stimulating PA among this large and growing group is of major relevance.
To stimulate people to positively change their PA behaviour, effective interventions are needed. A solid theoretical basis is an important prerequisite for the development of interventions to successfully change health behaviours [17]. A theoretical model that is frequently used to explain various health behaviours and is often used as a framework for the development of health education interventions is the Theory of Planned Behaviour [18]. This model states that behaviour is determined by intention to engage in the behaviour and perceived behaviour control over the behaviour as the most proximal factors. Intention itself is determined by attitude, social norm and perceived behaviour control [18]. Meta-analytic review studies found that the variables attitude, social norm and perceived behavioural control on average only explain 42–45% of the variance in intentions and that intention itself and perceived behavioural control only explain 27–36% of the variance in PA behaviour [19, 20]. This indicates that a large part of the variance in PA behaviour remains unexplained. Suggestions to improve the model have been brought forward by several researchers, like reconsidering the current constructs [21–23] or adding new predictors that significantly increase the explained variance of intention or behaviour [24, 25].
As assumed by several theoretical stage models, health behaviour change is a dynamic process, in which a person moves through a series of phases [26]. A key assumption of these theoretical stage models is that different determinants are important at different phases of behavioural change [26], indicating that the most important relevant determinants have to be specified for each phase separately. Based on health behaviour stage theories like the I-Change model [27–29], Precaution Adoption model [30] and the Health Action Process Approach [31–33], PA behaviour change is in this study distinguished into three main phases, which are awareness of insufficient PA, PA initiation and PA maintenance. First, awareness of insufficient PA is considered to be the first phase of PA behaviour change. Based on health behaviour stage theories, like the I-Change model [27–29], Precaution Adoption model [30] and the Health Action Process Approach [31–33], it is assumed that individuals only consider behaviour change when they are aware of their unhealthy behaviour. Individuals who are unaware of unhealthy behaviour do not perceive a need to change their behaviour into a healthier behaviour and will not proceed to the contemplation of change [34–38]. Important factors could for example be knowledge, risk perceptions and cues to prompt people to become aware [39]. Second, PA initiation is in this study defined as the period in which people become motivated to start being more physically active up to the initial PA implementation [39]. The PA initiation phase, can in accordance to the I-Change model, be distinguished into a motivational and a post-motivational phase [39]. The motivational phase includes the period of the process of thinking about becoming physically active and the decision to start participating in PA. In this motivational phase, an intention to become (more) active is formed. Important factors could be attitudes, self-efficacy expectations and social influence perceptions [39]. The post-motivational phase is the period of the formation of or the increase of one's PA level, up to the actual act of increasing one's PA level. In this post-motivational phase, people need to translate intentions into actions [39]. Important factors could be the planning and execution of several preparatory actions to facilitate PA [39]. Most studies on PA determinants have focussed on this initiation phase of PA [40]. Third PA maintenance in this study is defined as the period of sustained participation in regular PA for at least 6 months up to the development of PA as a habit [40, 41]. This phase can be determined by several post-motivational factors, like skills and strategies that facilitate sustained participation of PA and prevent relapse to inactivity [31, 39]. According to Dishman [42], most theoretical health behaviour models solely predict PA participation and initiation and fail to predict PA maintenance. Unfortunately, PA only results in health benefits when it is carried out for a longer period of time [40].
In several review studies on determinants of PA, determinants could be categorized into (i) social demographic determinants, (ii) personal and behavioural determinants, (iii) psychological determinants, (iv) social determinants and (v) determinants concerning the physical environment [43–46]. In a review of longitudinal studies examining the determinants of PA initiation and maintenance among older adults, the authors concluded that PA initiation was predicted by a different set of determinants than PA maintenance (van Stralen MM, Lechner L, Mudde AN, Bolman C, and de Vries H, in preparation). They found that the impact of outcome expectations, planning strategies and the source of social support differed with respect to predicting PA initiation and maintenance. This confirms the assumption of Sutton [26] and Rothman [47] that determinants could be phase specific, indicating that the most relevant determinants have to be specified for each phase separately. The authors also concluded that in the past decades, research on PA determinants among older adults primarily focused on the prediction of PA initiation and maintenance and concerned mainly personal and psychological determinants. No longitudinal studies were aimed at determinants of awareness of insufficient PA, and only a few studies examined the influence of post-motivational determinants, like implementation intentions, self-monitoring skills and experience of lapses and social and physical environmental determinants of PA initiation and maintenance (Van Stralen et al., in preparation). This despite the recent research interest in environmental determinants [48, 49] and theoretical models like the EnRG framework [50], the I-Change model [27–29], and the Health Action Process Approach [31-33] that recognize the importance of environmental determinants and/or post-motivational constructs. Hence, investigation is needed into these recent developed determinants (Van Stralen et al., in preparation).
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Delphi technique |
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In addition to the review of the literature, another way to explore relevant determinants of changing PA behaviour among older adults is a Delphi study. A Delphi study is a systematic approach, which aims to engage a large number of experts in a process to derive consensus in a group on a topic where the required information is incomplete or scarcely available [51]. A Delphi study begins with an open-ended questionnaire, which investigates the opinion of a panel of selected experts on a certain topic. In the subsequent rounds, a larger panel of experts rates the relative relevance of each item. The five categories of the determinants used in several review studies [43–46] were used as a basis for the categories of the second and third Delphi round. Through mostly three rounds, in which the panel is provided with controlled feedback regarding the groups mean scores, followed by a reinvestigation of their opinion, consensus about the topic is reached [52, 53]. The useful characteristics of Delphi study comprise (i) anonymity of experts, (ii) iteration, (iii) controlled feedback and (iv) statistical group response [54–56]. The first characteristic, anonymity of the experts—which is made possible by online computer communication—avoids specific group conformity and prevents influences of dominant others, prestige and politics. The second characteristic is iteration. Since a Delphi study is conducted in a sequence of rounds, the experts have the opportunity to adapt their opinion, which facilitates yielding of consensus. The use of controlled feedback in the sequenced rounds, the third characteristic, in which the panel of experts receive a summary of the results of a previous round, is a way to reduce noise in the results and also adds to reach consensus. Lastly, the fourth characteristic, the use of a statistical group response, reduces group pressure for conformity and to assure that the opinion of every expert is equally represented in the final round.
When compared with a review of the literature, a Delphi study on PA determinants has several advantages making the Delphi methodology a proper research method in addition to existing literature reviews [54]. First, while carrying out a Delphi study, there will be no difficulties of comparing different research designs, like quantitative and qualitative designs. Second, the Delphi technique provides the opportunity to evaluate PA determinants using a multiple-theory perspective. This contrary to the single-theory perspectives used by most PA determinant studies which can result in the exclusion of many other potentially relevant concepts related to PA [54]. Third, the Delphi technique can reveal and evaluate promising concepts related to PA, brought forward by only one panel member. Besides, new results and perspectives, which have not been studied among this specific target group, can in contrast to a literature review be integrated in to a Delphi study. When compared with other methodologies, the Delphi study technique was chosen above interview techniques like focus group interviews or semi-structured interviews. Since most of the invited experts were international, coming from 12 different countries (face-to-face) group discussions or interviews were found to be impractical [57].
By means of a Delphi technique, this study aims to give an overview of the most relevant determinants of awareness of insufficient PA, PA initiation and PA maintenance among older adults, in which it is aimed to (i) reach consensus among the experts about the most relevant determinants of the three phases of changing PA and to (ii) examine new concepts than have not been studied yet and that can be added to the list of most relevant determinants. A comparison of the results of the Delphi study with the results of the literature will be made in the discussion section.
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Method |
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A three-round Delphi technique was used in the study. After the first and second round, the experts’ opinions were analyzed and used for the next round questionnaire. In this study, two goals had to be achieved to identify determinants that experts collectively rate as important predictors of PA behaviour change. First, the perceived importance of each determinant under consideration in predicting a phase of PA behaviour change had to be assessed. In this study, this perceived importance was referred to as relevance of determinant. Second, the degree of consensus across the expert panel on determinants under consideration had to be assessed, also referred to as consensus.
First round
The first round was conducted to create an overview of possible determinants, divided into different determinant categories, for each phase. This overview was used to develop the questionnaire of the second round. To reach as much diversity in determinants as possible, researchers with different theoretical and professional backgrounds were invited to participate. The key-experts all were experienced in the area of theory-based research demonstrated by multiple international publications concerning predicting health behaviour and/or PA determinants. The key-experts were identified from database searches using Medline and Psychinfo and by examining relevant conference participants, reference lists from related papers, book chapters and review studies. To include a variety of insights, researchers with different theoretical and professional backgrounds were invited to participate. First, diversity of theoretical background was assured by inviting researchers specialized in the most known and used theoretical models, based on relevant journals and relevant state of the art books. Second, to ensure the professional background on research in health promotion researchers with a professor degree or PhD degree on studies about PA promotion or PA determinants among older adults were invited. Third, to guarantee the professional basis in the field, professionals in the field with coordinating functions in national health promoting projects or in national institutions, and with research experience, were included. A group of 32 key-professionals in both research and practice were invited to participate in the first round. Each key-expert was invited by e-mail to participate in the three rounds of the Delphi study. A link to the online first round questionnaire was included. The questionnaire was in English. It was also possible to complete the questionnaire by telephone. After one week, non-responders received a reminder. In total, 17 key-experts (response rate 53%) completed the questionnaire, 16 completed it online and 1 by telephone. All key-experts, from in total five different countries, had multiple research experience. Nine key-experts had a professor degree, seven had a PhD degree and one had an MSc degree.
Questionnaire
The online questionnaire consisted of nine open-ended questions. Since many key-experts were derived from a broader field than the specific research topic, the key-experts were explicitly asked to apply their (broader) knowledge to this specific target group and target behaviour. For each phase of PA behaviour change—awareness, initiation and maintenance—and for three broad categories of determinants—personal, psychosocial and environmental—key-experts were asked to name the factors that were relevant predictors among the over-fifties. For example: ‘In your opinion, what personal determinants could be relevant in maintaining PA behaviour among older adults?’
Data analysis
The responses of the key-experts were analyzed and listed to build the second round questionnaire. Two members of the research team separately and independently analyzed the responses of the key-experts, in which all determinants were put into a list. Analysis consisted of comparing the responses of the key-experts to a pre-developed coding scheme. This content analysis [58] consisted of five categories—social demographic, personal and behavioral, psychological, social and environmental determinants—which were based on the determinant categories as used by several literature reviews [43–46]. Similar responses were identified as the same determinant. When both research team members did not agree on a certain item, a third research team member was approached to reach consensus. In total, 73 items were identified as possible determinants of one of the three phases of PA behaviour change.
Second round
One hundred and ninety first and second authors of scientific papers in the field of health behaviour theories or the specific field of PA determinants received an e-mail invitation to participate in the second and third round of the Delphi study, which included the link to the second round online questionnaire. The authors were identified from database searches using Medline and Psychinfo and by examining reference lists from related papers, book chapters and review studies. The search covered the period from 2000 and 2005. Key-words used for database searches were a combination of PA, exercise, determinants, correlates, awareness, initiation, maintenance, randomized controlled trial, intervention, older adults and elderly. Researchers with different professional backgrounds were invited to participate. All key-experts who participated in the first round were also invited to participate again. After 1 week, non-responders received a reminder. One hundred and eighteen experts completed the questionnaire (response rate 62%), including 15 key-experts of the first round. All experts, coming from 12 different countries (mainly from countries out of western Europe, North America and Australia) had experience in theory-based research demonstrated by at least one international publication in the field of predicting health behaviour, PA promotion and/or PA determinants. Twenty experts had a professor degree, 69 a PhD degree and 29 an MSc degree.
Questionnaire
The questionnaire consisted of 219 structured questions (3 phases x 73 items) based on the determinants pointed out by the key-experts in the first round (see Table I). The experts were asked to rate on a 10-point Likert scale (1 = not at all relevant, 10 = outstanding relevant) the relevance of each determinant for, respectively, awareness, initiation and maintenance of PA behaviour of older adults. An example of a question is ‘How relevant are the following psychological determinants for, respectively, awareness, initiation and maintenance of PA behaviour of older adults’ (1 = not at all relevant, 10 = outstanding relevant): ‘Awareness of the personal relevance of being physically active’ or ‘Attitudes towards PA’.
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Data analysis
The median score, also referred to as the 50th percentile score, was calculated for each item to score the relevance of each determinant. The interquartile range (IQR) score was calculated to asses the extent of agreement between the experts about the scored relevance [59, 60]. The IQR represents the distance between the 25th and 75th percentile values, with smaller values indicating higher degree of consensus. An IQR score of 1 means that 50% of all the scores given by the experts fall within one point on the scale. According to Linstone and Turoff [55], an IQR
2 can be considered as good consensus on a 10-point Likert scale. SPSS version 11.0 was used for the analyses.
Third round
All respondents of the second round (N = 118) were invited by e-mail to participate in the third round including the link to the third questionnaire. After 1 week, all non-responders received a reminder. Seventy-three experts completed the third questionnaire (38% total response rate, 62% response rate of second round respondents), including 12 key-experts of the first round.
Questionnaire
In the third round, the experts received an adapted version of the questionnaire of the second round, together with feedback about the group median score for each determinant [59]. Only items for which there was a lack of agreement (IQR > 2) were included into the third questionnaire. A total of 146 out of the original 219 items were included into the third questionnaire. Participants were given the opportunity to rescore the relevance of each item taken the given feedback into account.
Data analysis
Again the group median score and IQR were calculated to determine the level of agreement as to the relevance of each item [59, 60]. To test the existence of iteration, changes in consensus between the second and third rounds were evaluated using the Wilcoxon signed-ranked test. Determinants were indicated as relevant if they scored 8 or higher on the 10-point Likert scale. Items that had a median relevance score of 8 or higher and that reached consensus (IQR 2) were included into the final list of relevant PA determinants.
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Results |
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First round
Since the responses of the key-experts of the first round were used as questions in the second round, the results of the first round are shown as the question items in Table I. The table lists all determinants that were mentioned in round 1. In total, 73 determinants were mentioned as possible determinants of one of the three phases of PA behaviour change. Respectively nine, six and four items represented the potential social demographic, personal and behavioural determinants. Thirty-one items were identified as possible psychological determinants, 12 items as possible social determinants and 11 items as possible physical environmental determinants.
Second round
The results of the second round are shown in Table I. In total, on 73 items consensus was reached (IQR 2). On 5, 41 and 27 items, consensus was obtained for predicting, respectively, awareness, initiation and maintenance of PA. Among the 73 items that obtained consensus, in total 26 items were indicated as relevant predictors (median relevance score 
8). Of these 26 items, the experts agreed on 2 items as relevant determinants of the awareness phase, 10 items as relevant determinants of the initiation phase and 13 items as relevant determinants of the maintenance phase.
Third round
The results of the third round are also shown in Table I. In total, of the 146 depicted in the third round questionnaire, all items, except one, obtained consensus (IQR 2). Of these 145 items that reached consensus, in total four items were indicated as relevant (median relevance score 8).
Taken both rounds into account, the experts agreed on 30 items to be relevant in changing PA behaviour. To specify, of these 30 items, the experts agreed on four items as relevant determinants of the awareness phase, namely the behavioural factors’ previous and current exercise behaviour and the psychological factors’ awareness of personal relevance of being physically active and awareness of the personal lack of PA. Ten items were identified as relevant determinants of the initiation phase, namely the personal factors’ functional limitations and physical health status, the behavioural factors’ previous and current exercise behaviour and having a busy life, the psychological factors’ intention to be physically active, self-efficacy to change/maintain PA, perceived barriers, goal setting/implementation intentions and the environmental factor perceived access to facilities. Sixteen items were identified as relevant determinants of PA maintenance, namely the personal factor physical health status, the behavioural factors’ previous and current exercise behaviour and having a busy life, the psychological factors’ enjoyment, intrinsic motivation, self-efficacy to change/maintain PA behaviour, will-power, commitment, integrating PA in the daily routine, and coping skills to resist temptations to relapse; and the social and physical environment factors meeting social needs, having a sports partner, social support from significant others and the stability of the social and physical environment. A summary of the items on which the experts agreed on to be relevant per phase of PA behaviour change are shown in Table II.
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The consensus significantly increased in the third round. When compared with the second round, larger consensus was found in the third round for the determinants of the awareness phase (z = –7.292, P = 0.000), the initiation phase (z = –5.003, P = 0.000) and the maintenance phase (z = –5.984; P = 0.000).
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Discussion |
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The aim of the study was twofold. The fist aim was to reach consensus among the experts in the field in order to obtain an overview of the most relevant determinants of becoming aware of PA, initiating PA and maintaining PA among older adults. Second, it was aimed to identify relevant new concepts as possible PA determinants among older adults. Resulting from the three rounds of the Delphi study, the experts agreed on 30 determinants to be relevant in changing PA among older adults. According to the experts 4, 10 and 16 determinants are relevant in predicting, respectively, awareness, initiation and maintenance of PA. The study allows several conclusions to be drawn.
First, both similarities as well as dissimilarities in determinants between the three phases were found. The only determinants that were considered to be relevant for awareness, initiation as well as maintenance of PA were previous exercise behaviour and current exercise behaviour. In addition, determinants that were indicated to be relevant for both initiation and maintenance were physical health status, having a busy life and self-efficacy to change/maintain PA behaviour. However, besides these similarities, much dissimilarity in determinants of awareness, initiation and maintenance was found, suggesting that most determinants were phase specific. In general, awareness-related issues were indicated by the experts to be relevant for the awareness phase. For initiating PA, the motivational-related issues of the psychological determinants, like intention, self-efficacy to change and perceived barriers, were considered to be relevant. While for maintaining PA, post-motivational-related issues of the psychological determinants, like commitment, integrating PA in the daily routine and coping skills to resist temptations to relapse, and social-related issues, like meeting social needs, having a sports partner and social support from significant others, were considered to be relevant. Researchers could use this information to fine-tune future interventions.
Second, when compared with the longitudinal studies examined in the literature review of Van Stralen et al. (in preparation), the Delphi study pointed out several other concepts as possible PA determinants among older adults. The behavioural-related items’ previous and current exercise behaviour and the awareness-related items’ awareness of personal relevance of being PA and awareness of the personal lack of PA were indicated by the experts as relevant predictors of the awareness phase of PA behaviour. However, in the literature no longitudinal studies were found that examined predictors of awareness of PA among older adults (Van Stralen et al., in preparation). This implicates that further research should focus on the importance of awareness and its determinants.
With regard to the initiation phase, the importance of several determinants considered to be relevant could be confirmed by the results of longitudinal studies. Several longitudinal studies found a positive influence of functional limitations [61], previous exercise behaviour [62], current exercise behaviour [63–66], physical health status [63-66], self-efficacy to change/maintain PA behaviour [61–64, 67–75], setting goals/implementation intentions [76–79] and perceived access to facilities [80] on PA initiation among older adults. Limited support was given by longitudinal studies for intention [63, 64, 67, 68, 81, 82] and perceived barriers [65, 75] in predicting PA initiation among older adults.
With regard to PA maintenance, the relevance of several determinants as indicated by the experts could be confirmed by the results of several longitudinal studies. Several longitudinal studies supported the relevance of previous exercise behaviour [67, 83, 84], current exercise behaviour [62, 66, 71, 83, 85], physical health status [61, 86, 87], psychological outcome realizations [88–90], self-efficacy to change/maintain PA behaviour [62, 66, 68, 71, 73, 74, 84, 87, 91–94], and enjoyment [74] on maintaining PA among older adults as indicated by the experts. Some evidence was found for the predictive value of having a sports partner and social support from significant others [66, 74, 95]. In the literature, no longitudinal studies among this age group was found for some recently developed concepts, like will-power, the psychological post-motivational determinants commitment, integrating PA in the daily routine, coping skills to resist temptations to relapse; and the social and physical environment-related factors meeting social needs and the stability of the social and physical environment (Van Stralen et al., in preparation).
The lack of longitudinal evidence for determinants considered to be relevant, such as several awareness-related, post-motivational-related and social and physical environment-related factors, suggests that the Delphi study is a good way to add new or promising concepts to the list of relevant PA determinants. Longitudinal research is needed to test if these concepts do predict PA behaviour among older adults.
Furthermore, differences in number of determinants between the phases were found. The small number of determinants considered to be relevant for the awareness phase could be explained by the lack of knowledge among the experts about the awareness phase and its predictors, since no longitudinal research has been conducted yet that examines the determinants of the awareness phase (Van Stralen et al., in preparation). Besides, awareness could be a difficult concept to grasp in terms of determinants, since it could be unclear to determine the direction of causality between awareness and its related factors, as specified by some of the experts. Furthermore, the amount of determinants considered to be relevant for the initiation phase falls far behind the amount of determinants considered to be relevant for the maintenance phase. This may also be explained by the amount of knowledge on these topics and the strong emphasis on PA initiation in empirical research. Since most theoretical health behaviours have been developed to predict actual PA participation or PA initiation [42], a lot of knowledge among the experts exists about PA initiation and its predictors. This results in a high agreement about concepts that are relevant in predicting initiation but also about concepts that are not. This explains the high consensus (56%) in the second round for the determinants of initiation. Since there is a growing interest into stimulating maintenance, many promising concepts exist that have the potential to predict maintenance. However, because of the lack of longitudinal research, the relevance of these potential predictors has not yet been confirmed or rejected in longitudinal research. This explains the high number of possible relevant determinants indicated by the experts together with the low consensus after the second round for PA maintenance (29%).
Some methodological restrictions of the study have to be taken into consideration. First, the method used to identify the potential experts for the Delphi study relied on published literature and knowledge of the research team. Besides, not every expert was reached or did respond to the questionnaire. Therefore, the results of the studies may not be totally representative for the opinion of all experts in the field. Furthermore, all experts and their opinions were equally weighted in the analyses. Experience and level of expertise might have differed between the experts, resulting in the underestimation of the opinion of highly experienced experts. Third, in this study the initiation phase was considered as a broad phase, combining both motivational and post-motivational processes. Next to practical reasons to enhance the feasibility to complete the study, this phase and its determinants is already the most studied and most known phase. By combining these specific processes of initiation, the experts could pay relatively more attention to the two other, more unknown, phases namely the awareness and maintenance phase. However, it is possible that some information about these specific processes of initiation could be lost. Fourth, because of a lack of empirical research on determinants of awareness and maintenance of PA, the opinion of experts may have been based on strong personal beliefs or guesswork, rather than on their understanding of the empirical evidence. This might also be a reason for the lack of consensus between in the experts after the second round on the determinants in the awareness and maintenance phase. Therefore, the results of the Delphi study need to be further tested and need to be confirmed in a longitudinal study.
Despite these limitations, our Delphi study suggested phase-specific PA determinants among older adults, as well as the need to analyze the impact of new and potentially relevant concepts and to verify new visions. A next step would be a longitudinal or experimental study to test its effectiveness. Our study provided an overview of the most relevant PA determinants, from a multi-theory perspective, according to the experts in the field. Some new and promising concepts were identified especially in the (post-motivation) psychological and social and environmental categories that can be tested in future longitudinal and experimental studies.
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Funding |
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Netherlands Organization for Health Research and Development (6100.0003).
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Conflict of interest statement |
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None declared.
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References |
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Received on January 9, 2008; accepted on July 27, 2008
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