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Conceptualizing and Defining the Intention Construct for Future Physical Activity Research

Rhodes, Ryan E.1; Rebar, Amanda L.2

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Exercise and Sport Sciences Reviews: October 2017 - Volume 45 - Issue 4 - p 209-216
doi: 10.1249/JES.0000000000000127
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Key Points

  • Intention has been an extremely important concept in physical activity theory and research by explaining and predicting behavior, providing a keystone for intervention and serving as a critical comparison for the relative value of volitional factors and non-conscious/automatic factors to behavior.
  • We overview the definition-level complexity of intention both from researcher and lay perspectives, provide evidence from studies conducted in our laboratory and general meta-analyses that the two intention concepts are measured differently, included in functionally different models, and show discrete findings when applied to explain physical activity motives.
  • We conclude with suggestions that decisional intention should be used to denote the direction of intention and intention strength should be used to denote the intensity of determination to improve measurement, theory testing, and intervention practices in physical activity research that uses an intention construct.

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Regular physical activity has been established as critical in the reduced risk of most major chronic diseases such as heart disease, type 2 diabetes, several cancers, and musculoskeletal disorders as well major psychological disorders such as anxiety and depression (36). Unfortunately, few people in most developed nations engage in regular physical activity (18). For example, in Canada, it has been estimated that less than 20% of adults are meeting physical activity guidelines recommended for these health benefits (150 min of moderate intensity activity) (8). Clearly, health promotion efforts are needed. To date, most health promotion efforts are driven by the aim to enhance people’s intention to be physically active; however, the concept of “intention” has been used to refer to multiple constructs. In this article, we are calling for clarity in the research and promotion of physical activity intention through investigation of the hypothesis that intention is a double-barreled construct with dual meanings. We propose that each intention construct has independent measurement requirements and can be differentiated by their relation as mediators of social cognitive constructs, as well as their application among popular theories of behavior change.

Theoretical understanding of the determinants behind health behaviors such as physical activity has been a line of research inquiry for over half a century (41). The premise behind this research is that a sound understanding of health behavior determinants will aid in intervention success. Theories represent an organizing framework to provide structure, function, and common nomenclature to critical variables under study (25). Although the breadth of theories applied to understand physical activity has been growing in diversity, the dominant approach by a wide margin has been through the social cognitive tradition. Theories from this tradition each have unique aspects, yet almost all suggest that expectations of the outcomes from behavioral action and the perception of one’s capability to perform the behavior affect the formation of intention. Intention, in turn, is considered the proximal impact on behavior. These theories include, but are not limited to, the theory of planned behavior, theory of reasoned action, protection motivation theory, variants of social cognitive theory, variants of self-determination theory, and even stage models such as the transtheoretical model or precaution adoption process, where stage of change is an intention-behavior hybrid construct (for a complete list, see (25)).

Social cognitive approaches to understanding physical activity have been useful but are not without some limitations that have been a subject of recent debate (44). One of the most common criticisms is the modest association between intention and behavior, when these theoretical models tend to suggest that intention should be the critical proximal determinant of behavior (45). The criticism is interesting because the relation between intention and health behaviors is substantial. For example, the most recent meta-analysis of the theory of planned behavior applied to physical activity (23) showed that the correlation between intention and behavior was in the medium-sized (r = 0.48) range. With the possible exception of self-efficacy, intention is the largest and most reliable psycho-social predictor of physical activity (36). Thus, intention-based social cognitive models have strong support for their predictive capability.

Still, 77% of the variability in physical activity is unexplained, which is problematic mainly when intention is considered the gate through which all social cognitive expectancies must pass to affect behavior (45). The relation is also further attenuated when examining change in behavior (i.e., controlling for past behavior), which is more accurate when attempting to understand intention and its role in behavior change (50); the relation between physical activity and intention reduces to a small (r = 0.22) effect (23). Examinations of the absolute, rather than relative, value of intention-behavior relations also have shown considerable discordance (43). Experimental manipulations that increase physical activity intention (d = 0.45) result in much lower, and clinically less meaningful increases in physical activity (d = 0.15) (34). Dichotomization of the intention and physical activity relation around public health guidelines also showed that 48% of intenders failed to follow through with physical activity (32). Perhaps, most important is the lowered practical value of theories that place intention as the proximal antecedent of physical activity. It is extremely common for participants in interventions to report to the trial with high intentions at baseline — often an almost circular reasoning for even volunteering in the first place — yet low participation in physical activity (33).

These challenges to the intention construct have, in part, produced a growing body of research on other mechanisms that may directly explain physical activity such as the role of volitional factors (4,42) and non-conscious/automatic processes (28,44). Although the exploration of these additional factors in explaining physical activity is clearly needed, we propose that a better understanding and fine-tuned conceptualization of the intention construct is warranted to improve these lines of research and the valid testing of various social cognitive models. Specifically, we hypothesize that the intention concept encompasses two empirically and conceptually distinct meanings: a decision to perform physical activity and the commitment to enact that decision. Although this double-barreled definition was present and identified during the inception of social cognitive models, we propose that it has not been adequately addressed and has created challenges across model development, intention measurement, and testing in the physical activity domain. The purpose of this article is to 1) overview the definition-level complexity of intention both from researcher and lay perspectives; 2) provide evidence from studies conducted in our laboratory and meta-analyses that the two intention concepts are measured differently, included in functionally different models, and show discrete findings when applied to explain physical activity motives; and 3) provide examples for how the two intention concepts have dramatic differences in application to physical activity intervention design and implementation. We conclude the article by providing recommendations for how to reduce this complexity moving forward and offer suggestions for researchers and practitioners who use the intention construct to understand and change physical activity.

The Conceptualization of Intention

To understand the meaning of intention, we believe that it is useful to assess both the lay interpretation of the word and researcher-based definitions. Marked discrepancies between these definitions would suggest that the research concept may be jargon and pose potential problems for interpretation and measurement among participants. Furthermore, complicated definitions with multiple interpretations suggest complexity of a term that may bias theory testing. To demonstrate lay interpretations of “intention,” we used the definitions from the top five best-selling English language dictionaries from, along with the definition from a commonly used web dictionary source (12) and the American Psychological Association’s Dictionary of Psychology (2). In an effort to demonstrate how intention has been defined and measured by exercise researchers, we conducted a literature search of articles published between January 2012 and January 2017 using Google Scholar with the in-title search terms intention and exercise or physical activity. Within the 230 relevant publications, citations for “intention” were tracked to the original sources of conceptualization of “intention.” Table 1 outlines the dictionary definitions of intention, whereas Table 2 outlines researcher definitions of intention.

Dictionary definitions of “intention.”
Researcher definitions of “intention.”

Supportive of our hypothesis, two clear themes emerged from the seven dictionaries surveyed in Table 1. All seven dictionaries described intention as a mental aim or determination for a specific end state, highlighting a binary decision (2,6,12,22,24,26,48). Three of the dictionaries defined intention as a degree of determination or wanting, highlighting a continuum of motivational intensity (6,12,24). Only one of these definitions chained these themes to suggest the amalgam represented the definition of intention (6). There is clear lack of agreement on whether intention is the mere mental representation of a decision or the commitment to act.

Interestingly, a similar dichotomy in the meaning of intention, followed by a mix of use of each theme, was present among the nine researcher-based definitions in Table 2. Five researcher definitions equated intention as synonymous with a decision or aim toward a specific end state mental plan (3,5,15,19,21). For example, Gollwitzer (15) describes intentions as “the goal state or desired outcome specified by the wish thus becomes an end state that the individual feels committed to achieve” (p. 57). Bagozzi (3) divides intentions into three types, strictly based on the type of outcome one is striving toward (i.e., present oriented, future oriented, and goal directed). Seven researcher definitions were explicit that intention included an intensity in the determination to act (1,5,7,14,19,21,49). For example, Ajzen (1) described intention as “the motivational factors that influence a behavior” (p. 181) and Cane et al. (7) suggest intention is “the resolve to initiate or terminate a behaviour” (p. 12). Like the dictionary definitions in Table 1, researchers did not express clarity across these themes. Two of the definitions seemed exclusive to the decisional representation of intention (3,15), four researcher definitions seemed exclusive to the intensity of determination theme (1,7,14,49), and three researchers expressed that both decision and intensity themes represent intention (5,19,21). For example, Lewin (21) described intentions as having a motivational and then a choice phase and Bruner (5) suggested intention captures operational persistence toward an end state as well as a choice among possible alternatives.

The point here is not to highlight any specific researcher or dictionary definition of intention. The evidence indicates that intention has a double-barreled meaning, and the application of either meaning or both meanings is not reliable. Importantly, the two meanings of intention are present across dictionaries and researchers, indicating that differences in the use of the intention term are not from mere research jargon. People may be drawing upon any or all of these meanings when answering physical activity questions that include “intention” as the key descriptor. Thus, it is important to examine whether this lack of clarity within the intention construct may be affecting model development and testing in physical activity research.

The Measurement of Intention

As hypothesized, the two definitions of intention have different underlying distributions of response, based on the two meanings (Fig. 1). Sheeran (2002) notes intention, as conceived as a decision, merely reflects direction (to do X vs not to do X), a point also made more recently by Fishbein and Ajzen (14). This is measured in a binary/dichotomous form or via open-scaled formatting that allows participants to describe the direction of intent (10). Thus, an item with the phrase “I intend to be physically active five times over the next week” with yes/no response options or “I intend to exercise ____ days per week” with an open choice of formatting presumably assess this decision but not the intensity of determination. By contrast, when intention is measured as a reflection of intensity of determination, it seems inherently continuous (14). An item that asks participants to rate their determination to be physically active at least five times over the next week with Likert-type scaling of strongly agree to strongly disagree is positioned to assess the intensity of this determination (9). Table 3 provides examples of measurement and analysis strategies for empirical use of intention direction and intensity.

Figure 1:
Conceptual differences and overlap of the two intention concepts.
Description of intention decision and commitment with measurement and analyses examples

The subsequent measurement of these two meanings of intention is easily observable among some of the most popular physical activity theories. For example, stage theories use a binary algorithm to assess intention (27). A similar dichotomization of intention (intend/do not intend) and behavior (success/failure) is present in the physical activity action control framework (32,33,43). By contrast, the theory of planned behavior, variants of social cognitive theory, protection motivation theory, and the health action process approach use a fixed statement (e.g., "I intend to exercise X times per week") and response options that allow respondents to grade the intensity of their agreement (e.g., strongly disagree to strongly agree) (9). Clearly, both meanings of intention are measured differently and with frequent application in the physical activity domain.

The Relation of Intention With Behavior and Social Cognitive Constructs

The definition of intention in a theory is as important to structure as measurement. Courneya (10) provided an early test of the predictive capability of intention direction (dichotomous) and intensity (continuous) and showed that intensity had a significantly larger association (r = 0.71 to 0.51) than direction (r = 0.66 to 0.43) in several tests. Thus, the two types of intentions are not functionally equivalent predictors of physical activity behavior.

The mediation of social cognitive variables through intention also differs by direction and intensity, as hypothesized (Fig. 2). This is evident both directly in comparisons within the same data set and indirectly through meta-analyses of different theoretical approaches. For example, in a study from our laboratory, 298 undergraduate students completed measures of the theory of planned behavior and a self-reported follow-up of moderate and vigorous intensity physical activity 2 wk later. When a measure of the direction of intention was used, intention failed to account for the relation between behavior and affective attitude, instrumental attitude, subjective norm, and perceived behavioral control (30). By contrast, when a measure of the intensity of determination was used, instrumental attitude and subjective norm did not have a direct relation with behavior, whereas affective attitude and perceived behavioral control did show significant direct effects (31). A similar finding was identified for a random sample of 1192 Canadian adults who completed social cognitive measures of the transtheoretical model and self-reported moderate to vigorous physical activity 6 months later. When a measure of the direction of intention was used, intention failed to account for the relation between behavior and self-efficacy, pros, and cons; only the cognitive processes of change did not have a direct relation with physical activity (38). By contrast, only self-efficacy explained physical activity independent of intention when a measure of intensity was used (37).

Figure 2:
Schematic of the mediation capability of decisional intention and intention strength.

Evidence that measures of direction and intensity of intention are not functionally equivalent also has been shown in proxy constructs, such as parental support behavior for child physical activity. For example, in a random sample of Canadian mothers (N = 1253) of children aged 5 to 12 years, intention to support child physical activity, measured as intensity, mediated the relation between support behavior 6 months later and theory of planned behavior constructs of instrumental attitude and affective attitude but not perceived behavioral control (40). However, when intention was measured as a direction, only instrumental attitude had evidence of mediation (39).

Similar results for how the two concepts of intention relate to physical activity and social cognition are evident in meta-analyses and reviews. In assessments of the theory of planned behavior, which uses the intention concept of intensity, perceived behavioral control/self-efficacy has had either mixed support (17) or no support (23,47) for a direct effect on behavior after controlling for intention and these reviews do not indicate support for direct effects of attitudes or subjective norm (17). By contrast, review of the transtheoretical model, which uses a direction measure of intention (contemplation vs behavioral stages), supports direct relations with physical activity between self-efficacy and pros and cons (conceptually similar to attitudes) after controlling for intention (46). Similarly, a review of the action control framework, which uses a measure of intention correspondent with direction, also found that instrumental attitude and subjective norm did not have direct overall effects on physical activity after accounting for intention, but affective attitude and perceived behavioral control did have direct effects (33).

In summary, the cumulative results support our hypothesis that there are meaningful empirical differences between the two concepts of intention. Intention, when positioned as a concept of intensity to enact physical activity, is a better predictor of behavior and a more robust mediator between behavior and social cognitive constructs than the concept of intention when positioned as a decision to perform regular physical activity.

Application to Physical Activity Theory Testing and Intervention Design

These two meanings of intention can have very different implications for theory. Our recommendation is for researchers to state the type of intention concept conceptualized and measured in the health behavior model with the rationale for its use. Table 3 and Figure 3 outline some of the matches of intention by popular or emerging physical activity behavior models, yet the list is not meant to be definitive or exhaustive. For example, if intention is conceived as intensity of commitment, it stands to reason that the construct represents the final and definitive culmination of deliberate motivation upon behavior (1,20). In the previous section, we provided evidence for this assumption, as the intensity concept of intention was a superior mediator of social cognitive constructs compared with the direction concept of intention. Thus, intention, when defined as the intensity of commitment, can involve tests of dual process models (11) or volitional behavior sequence models (16) because the intention construct is a summary concept for all conscious motivation. For example, the action phase model (20) suggests that planning is a postintentional construct and makes the conceptualization very clear that postintentional is equivalent to postmotivational.

Figure 3:
Schematic of the application of decisional intention and intention strength to physical activity theory testing.

By contrast, if intention is conceived as mere direction, this would not necessarily indicate the final and definitive motivational variable. Instead, it may be an indicator of a process in physical activity decision-making and subsequent enactment (29). In these cases, motivational factors, volitional factors, or automatic factors may still contribute to the enactment of the intention, and thus postintentional does not equate to postmotivational. Our previous section showed evidence for this approach because perceived behavioral control and affective attitude were relatively consistent predictors of physical activity independent of the direction concept of intention, but instrumental attitude and subjective norm often were mediated by intention. The definition of intention as a decisional direction allows for the examination of pre- and postdecisional constructs in the process of health behavior change and the interaction between direction, volition, and motivation.

These differences in theory also translate to applied differences in intervention design. If interventionists are interested in the formation versus enactment of decisions such as New Years physical activity resolutions, opting into weight loss programs, or volunteering for randomized controlled trials, then intention models that use the concept of direction seem suitable. These types of programs clearly involve uniformity of direction in intention, and the focus of intervention is on postdecisional variables but not necessarily postmotivational variables. For example, the multiprocess action control framework (29) suggests that instrumental outcome expectations of health and social benefit as well as basic capability to perform the behavior are largely predecisional aspects that contribute to the intention to be active but not the enactment of behavior. By contrast, the affective aspects associated with physical activity (enjoyment) and opportunities to be active (social and built environment) continue to be important to intervene upon during enactment of the activity along with self-regulation skills (plans, monitoring) and the formation of habit and identity. The transtheoretical model (27) has a more complicated algorithm of stages between intention and behavior that has some controversy but generally suggests that predecisional populations should have a focus more on the benefits of physical activity and cognitive processes of change, whereas postdecisional factors should focus on behavioral processes of change and reduction of barriers.

Intervention design using the intensity concept of intention seems suitable to apply across any population for physical activity intervention where motivation (intensity of determination) is variable, but may be particularly interesting when comparative concepts of volition and automatic processes are of interest. This concept is recommended for use when researchers wish to evaluate the relative contributions of motivation compared with automatic or implicit processes on behavior (11). Similarly, the intensity of intention concept seems of better use for examining the relative intervention contribution of motivational and volitional processes on physical activity behavior (4,42) than direction of (decisional) intention. Decisional intention may be of use to examine how automatic or volitional factors interplay with decision-making and behavioral enactment, but the concept is not meant to include the entirety of the motivational spectrum and thus would not represent an adequate conceptualization to understand the relative contributions of motivational, automatic, and volitional factors in intervention.

Recommendations for Moving Forward

Our analysis shows clear support that intention encompasses two conceptually and empirically distinct meanings in physical activity research. Thus, there is futility in moving forward by suggesting a singular meaning for intention — the concept is complex — and an attempt to define intention with a singular meaning is not commensurate with the history of this concept in research or in lay vocabulary. Furthermore, our overview of the conceptual and empirical application of intention to physical activity demonstrates that both meanings may have use in theory and underlie different measurement requirements. This suggests that continuing with the double-barreled meaning of intention is adding confounds to measurement, application, and testing of physical activity theory. Clarity of the concept is helpful, particularly as intention-based theories are being challenged for their utility in health behavior research. For example, an intention-behavior gap that represents the discordance between a decision to enact a behavior and the commitment to enact a behavior seems substantively different, yet both remain relevant and important in physical activity science.

We suggest that the two meanings should still retain the wording of intention, to tie the concepts to past history, yet both concepts require an additional word to clarify what meaning of intention is being put forward. We suggest decisional intention to represent the direction meaning of intention. This includes the presence or absence of self-instructions, an aim, or outcome plan. We suggest that intention strength be used to represent the commitment to enact behavior. This term dates to the original theorizing of Fishbein and Ajzen (13) and represents the magnitude of commitment, effort, and motivation one is willing to engage in to enact a behavior. We recommend that these terms be used whenever the intention concept is applied to physical activity theory testing to provide clarity from this point forward.

With these terms established, adequately powered psychometric testing of measures of decisional intention and intention strength would be helpful. For example, decisional intention can be measured with dichotomized measures, or open-scaled choice options (10), but this would not be appropriate to measure intention strength, because that concept represents a continuum of commitment. Furthermore, given the complicated meaning of the intention term, it would be useful to measure both of these constructs with items that make their conceptual distinction clear. It also would be prudent to use terms like “decision” or “aim” to avoid any confounding responses of decisional intention with intention strength. More consequential, we do not recommend the use of “intention” as an item key word for the measurement of intention strength. This is because it is not clear which meaning of the “intention” wording respondents are using when answering the item. For example, respondents could be answering that they strongly agree that they have made a decision to enact a behavior or that they strongly agree that they are determined to enact the behavior. In support of this recommendation, there is evidence to suggest that intention strength can be a superior predictor of behavior when measured with items that avoid the complexity of the intention term (35). We recommend the use of items that use other descriptions of intention strength (e.g., willingness to try hard, effort, commitment, resolve) to avoid the potential confound from participants who use the decisional intention definition when answering items meant to assess intention strength.

We believe the distinction of these two intention terms also will improve the validity of future theory testing and intervention. Population-based studies on people’s decisional intention and intention strength are needed to identify potential at-risk populations and to determine whether there are systematic differences as a function of sociodemographic factors such as age, sex, or education. Prospective and intervention studies are needed to establish if certain intervention strategies are more or less effective for manipulating decisional intention or intention strength and the magnitude that changes in decisional intention and intention strength affect physical activity change.


Intention-based models have been extremely important to physical activity theory and research by explaining health behavior and serving as a critical comparison for the relative value of volitional factors and nonconscious/implicit factors. In this article, we demonstrated that the intention concept is complicated by a double-barreled definition in both the lay- and researcher-driven literature. Intention can mean a decision taken toward performing a behavior and/or the commitment to enact a behavior. We showed that the two intention concepts are not equal predictors of physical activity and do not operate the same as mediators of social cognitive constructs. We provided examples for how the complexity of the intention concept may affect model development, measurement, and intervention design. Based on this evidence, we suggest that decisional intention be used to denote the direction meaning of intention and intention strength should be used to denote the intensity of commitment. We suggest that holding to these terms will improve measurement, theory testing, and intervention practices in physical activity research that uses intention-based models.


R.E.R. is supported by funds from the Canadian Cancer Society, the Social Sciences and Humanities Research Council of Canada, the Heart and Stroke Foundation of Canada, and the Canadian Institutes for Health Research. A.L.R. is supported by funds from the National Health and Medical Research Council of Australia.

No funding for this article. The authors report no conflicts of interest.


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theory of planned behavior; stages of change; mediation; motivation; action control; attitudes; intervention

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