Regular physical activity has been established as a mechanism to prevent and treat various chronic illnesses such as heart disease, diabetes, cancer, obesity, osteoporosis and psychological ailments [1–4]. However, the majority of adults in industrialized nations are not physically active enough to accrue health benefits [1, 5–7]. In response to this important issue, researchers are investigating effective ways to increase physical activity by furthering our understanding of physical activity behaviour determinants in numerous settings .
The workplace has been identified by various governments [1, 9, 10] as a key setting to promote physical activity, due in part to the accessibility of people within their occupation . The majority of Canadian adults are in the workforce and spend half of their waking hours in a workplace environment . However, the modernization of today's workplaces has contributed to physical inactivity, as many workers are now sedentary during working hours . Thus, there is a potential for many people to benefit by effective workplace initiatives promoting physical activity during or outside of work time .
Most workplace physical activity interventions have been focused at the individual level focusing on providing employees with physical activity and health information and targeting psychological factors related to physical activity behaviour [4, 12–14]. Expected benefits and costs of performing a behaviour (i.e., outcome expectations), and one's belief that he or she is capable of performing a behaviour to get a desired result (i.e., self-efficacy), are constructs utilized from established cognitive-based theories, such as Social Cognitive Theory, to promote physical activity at the individual level . Based on reviews of the literature however, workplace interventions using such theoretical constructs as a basis for intervention have only been modestly successful at increasing physical activity involvement [11, 13].
Recent calls have been made to examine the potential of workplace environments for increasing employee physical activity levels using an ecologically-based approach [2–4, 12–14, 16, 17]. The essence of ecological models is an emphasis on the environments in which people interact, such as their home, work, sociocultural setting, and climate where they live . The ecological approach has been described as an attempt to simultaneously consider several levels of a person's life setting within an intervention .
As more focus is placed on employing an ecological approach in physical activity research, ecological models have emerged for understanding this behaviour. Recently, an ecological model for physical activity behaviour (Ecological Model of Physical Activity; EMPA) has been conceptualized . The EMPA provides a comprehensive ecological framework from which several testable hypotheses concerning physical activity promotion have been proposed .
Further, based on the work of McLeroy and colleagues  and Sallis and Owen , Plotnikoff and colleagues  developed an ecological workplace physical activity model identifying six overlapping environment levels in the workplace: (a) Individual (i.e., factors in the workplace addressing individual employee characteristics related to physical activity behaviour such as skills, knowledge, confidence, age, and gender); (b) Social (i.e., the influence of the corporate culture, social relationships, peer, and supervisor relationships related to physical activity behaviour of employees); (c) Organizational (i.e., infrastructure, leadership, and desire of the workplace to promote physical activity, how the organization is structured); (d) Community (i.e., how the workplace interacts, partners with, or utilizes other organizations, community-based resources or government bodies that may foster physical activity behaviour of employees); (e) Policy (i.e., the workplace's policies regarding employees' physical activity behaviour); and (f) Physical Environment (i.e., the physical environment of the workplace including the buildings, workplace grounds, and surrounding area related to physical activity behaviour of employees). Additionally, Plotnikoff and colleagues developed an instrument (i.e., Workplace Physical Activity Assessment Tool; WPAAT) by identifying elements in each level of the model suggested as best practices by both the literature and stakeholders to promote physical activity in the workplace . The WPAAT was designed to evaluate workplace physical activity programs using the ecological model as a framework.
Despite the emergence of ecological models to explain and promote physical activity behaviour [19, 22], more work is required given that the crux of ecological-based approaches runs contrary to traditional social-cognitive models of behavioural change [19, 23]. Social Cognitive Theory (SCT)  is similar to ecological models in the sense that it shares the perspective that environmental factors can be influential in shaping health-promoting behaviour [19, 23–25]. On the other hand, it has been argued that a defining feature of ecological models is a direct relationship between the environment and behaviour without cognitive mediation . Bandura describes this reasoning as 'unidirectional environmental determinism' that does not account for the bi-directional relationships he posits that occur between the environment and the person included in SCT (reciprocal determinism) . SCT further presumes that people are active shapers of their environments rather than merely passive reactors [24, 26].
There has been some research supporting direct relationships between the environment and goal-directed behaviours. Bargh and Gollwitzer  conducted a series of studies testing hypotheses of the auto-motive model of behaviour that purports links can develop between situational and environmental features and behaviour when an individual makes a consistent and frequent choice to fulfill a goal in a certain situation (e.g., being polite). Over time, when individuals enter the situation, their goal directed behaviour will be automatically activated without cognitive mediation . From Bargh and Gollwitzer's work, it seems reasonable to suggest that people with a long term goal to be physically active could be prompted to do physical activity in situations where they have continually chosen to be active over time, without cognitive mediation. This line of research however, has not been directly tested in the physical activity domain.
Conversely, other researchers have argued that factors in the environment provide a 'cue to decision' about whether to do physical activity, rather than a direct 'cue to action' . For example, seeing your running shoes could provide a cue to decide whether to engage in physical activity, rather than prompting one to automatically go for a run. Furthermore, it has been suggested that physical activity in particular, is a very cognitive-initiated activity, as it can involve much preparation and planning in today's modernized environment . In addition, physical activity interventions aimed solely at the environment may inadvertently instigate psychological alterations shaping behaviour change, such as influencing one's self-efficacy about engaging in physical activity.
In a more recent publication describing ecological concepts, Sallis and Owen  no longer describe the direct relationship between the environment and behaviour as a defining feature of ecological models, but acknowledge that the environment can, both directly and indirectly through one's perceptions, influence behaviour. This modified description resembles SCT's reciprocal determinism principle . Indeed, some theorists  have purported that ecological models are largely a mirror of SCT with multiple levels identified in the environment. Two potential research aims suggested by Spence and Lee  to further the understanding of ecological models in the physical activity domain are (1) to determine if a direct relationship exists between the environment and physical activity, and (2) to determine if psychological variables mediate the observed relationship.
The mediating effects of cognitive constructs, (e.g., self-efficacy and outcome expectations), can be tested on the relationship between ecological variables and physical activity using a series of multiple regression equations . In this type of analysis, the extent to which a variable (e.g., outcome expectations and self-efficacy) accounts for the relationship between a predictor variable (e.g., ecological variable) and a criterion variable (e.g., physical activity behaviour) is tested . A hypothesis guiding such an analysis would be that ecological variables are associated with physical activity participation, and this association is mediated by social-cognitive variables .
Recent calls have been made for mediation analyses to be conducted in order to guide development of physical activity interventions based on ecological models [8, 19, 23, 29, 30]. Current theoretical approaches focussed on psychological constructs (e.g., Transtheoretical Model, Theory of Planned Behaviour, Social Cognitive Theory) to predict physical activity have been quite limited, at best explaining about 30% of variance in physical activity, suggesting a more comprehensive understanding of physical activity determinants is needed [29, 31]. In a recent review of studies examining potential psychosocial mediators of physical activity, a dearth of such research was noted despite calls in the literature for such assessments . The aims of this study therefore, are to determine if (1) perceptions of the workplace environment are associated with the physical activity of employees and (2) if this relationship is mediated by self-efficacy and outcome expectations.