Social Cognitive Theory (SCT: Bandura, 1997) has been used successfully in understanding exercise adherence. To date, the majority of the exercise research has focused on situations of personal agency (i. e. , self as agent: e. g. , McAuley & Blissmer, 2000). However, there are a number of exercise situations in which people look to others to help them manage their exercise participation by enlisting a <i>proxy-agent</i> (Bandura, 1997). While using assistance from a proxy can promote the development of self-regulatory skills, Bandura (1997) cautions that reliance on a proxy actually reduces mastery experiences which can result in an inability to self-regulate one?s behaviour. Although research examined proxy-agency in exercise (e. g. , Bray et al. , 2001), the issue of reliance on the proxy at the expense of the participant?s ability to adjust to exercise without that agent has not been investigated. This potential dilemma of proxy-agency in exercise was at the core of this dissertation and was investigated in a series of three studies. Study 1 investigated whether those who differed in preferred level of proxy-contact also differed in their social-cognitions both within and outside a proxy-led exercise context. In addition, the relationships between proxy-efficacy, reliance and self-efficacy were examined. Results indicated that participants who preferred regular contact with an exercise proxy had lower self-regulatory efficacy, lower task efficacy, and weaker intentions in a proxy-led exercise context. Further, high-contact participants were shown to be less efficacious in dealing with the behavioural challenge of sudden class elimination. It was also demonstrated that higher reliance on the instructor was associated with lower self-efficacy and higher proxy-efficacy. Study 2 served to extend the findings of Study 1 through the examination of behavioural differences characteristic of differential levels of preferred proxy contact and the reasons for use of proxy-agency. It was found that exercise class participants preferring high contact with a proxy found exercising independently more difficult than did their low contact counterparts. It was also found that when faced with class elimination, those preferring high contact chose a self-managed activity alternative less frequently than did those preferring low contact. High contact participants also reported feeling less confident, less satisfied and perceived their alternative activity as more difficult than did those preferring low contact. In examining the reasons for preferring high proxy-contact, results indicated that a preference for high contact was associated with having had less experience exercising independently and allotting more responsibility for in-class participation to the class instructor as compared to preferring low proxy-contact. Study 3 used Lent and Lopez?s (2002) tripartite model of efficacy beliefs to examine the associations between relational efficacies (i. e. , other-efficacy and relation inferred self-efficacy (RISE) beliefs, proxy-efficacy) and various social cognitions relevant to proxy-agency. Results revealed that relational efficacies were distinct yet related constructs which additively predicted self-regulatory efficacy, satisfaction, intended intensity and reliance. Relational efficacies were also shown to make unique contributions to the predictions of the relevant social-cognitions. It was also demonstrated that RISE beliefs were associated with the attributions participants made. Specifically, higher RISE beliefs was associated with making more internal, personally controllable and stable attributions. These results represent the initial examination of relational efficacy beliefs in the exercise literature and provide additional evidence of the proxy-agency dilemma in exercise. Taken together, the present series of studies both support theorizing by Bandura on the dilemma of proxy-agency and represent an extension of the existing literature of proxy-agency in exercise. Results suggest that seemingly healthy, regularly exercising adults who choose to employ proxy-agency may be at risk for nonadherence in situations of behavioural challenge. The current findings have important implications for exercise leaders and interventionists as they must be aware of the balance between helping and hindering.

The self has been identified as the ?psychological apparatus that allows individuals to think consciously about themselves? (Leary & Price Tangney, 2003, p. 8). Further, the self has been identified as a worthwhile construct of investigation in relation to health behaviour (Contrada & Ashmore, 1999). Two self-related variables that have been useful in the study of health behaviour are <em>identity</em> (e. g. Anderson, Cychosz, & Franke, 1998; Petosa, Suminski & Hortz, 2003; Storer, Cychosz, & Anderson, 1997) and <em>self-efficacy</em> (Maddux, Brawley & Boykin, 1995). Identity Theory posits that individuals regulate their behaviour in a manner that is consistent with their goal identity (Gecas & Burke, 2003). Social Cognitive Theory provides a means of measuring social cognitions that may be important in behavioural regulation relative to identity. Further, self-efficacy beliefs may influence individuals? persistence at aligning their identity and behaviour. Research to date has investigated the link between identity and exercise (e. g. Anderson, Cychosz & Franke, 1998; Petosa, et al. , 2003). Further, researchers are beginning to investigate the link between identity and other health behaviours (e. g. Armitage & Conner, 1999; Kendzierski and Costello, 2004; Storer, Cychosz, & Andersen, 1997). However, research has not utilized the predictive frameworks offered by Identity Theory and Social Cognitive Theory to investigate the relationships between identity, behaviour and behavioural regulation. <br /><br /> Study One investigated the role of identity and self-efficacy beliefs in the maintenance of vigorous physical activity. Results were consistent with both Identity Theory and Social Cognitive Theory. Individuals who strongly identified with the runner identity expressed stronger task and self-regulatory efficacy beliefs. They also exercised more frequently and for longer durations than did those who only moderately identified with running. <br /><br /> Study Two further explored the relationship between exercise identity, exercise behaviour and the self-regulatory processes involved in behavioural regulation. Identity Theory and Social Cognitive Theory were used as guiding frameworks for this investigation. High and moderate exercise identity groups were compared in term of their affective and cognitive reactions to a hypothetical behavioural challenge to exercise identity. Consistent with Identity Theory, results indicated that participants appeared to be regulating their behaviour in a manner that was consistent with their exercise identity. Specifically, in response to the behavioural challenge to identity, high exercise identity participants, in contrast to their moderate counterparts, showed (a) less positive and (b) greater negative affect about the challenge, (c) higher self-regulatory efficacy for future exercise under the same challenging conditions, (d) stronger intentions for this future exercise, as well as for (e) using self-regulatory strategies to manage the challenging conditions and (f) intending to exercise more frequently under those conditions. <br /><br /> Study Three investigated whether identity with <em>healthy eating</em> could also be useful in understanding behaviour and behavioural regulation. Similar to Study Two, extreme healthy-eater identity groups? reactions to a hypothetical behavioural challenge to identity were compared. Results were similar to Study Two. Participants responded in a manner that suggested that they would regulate their future behaviour relative to their healthy-eater identity. In response to the behavioural challenge to identity, individuals who highly identified as healthy-eaters expressed less (a) positive affect, greater (b) negative affect, (c) self-regulatory efficacy for managing their healthy eating in the future challenging weeks, (d) intentions to eat a healthy diet, (e) generated more self-regulatory strategies and had (f) stronger intentions to use those strategies in future weeks under the same challenging conditions than did individuals who moderately identified themselves as healthy-eaters. Further, prospective relationships between healthy-eater identity and social cognitive variables, and healthy eating outcomes were examined. As was found in Study One in the context of exercise, healthy-eater identity and social cognitions predicted healthy eating outcomes. <br /><br /> Taken together, the three studies suggest that identity may be important in understanding health behaviours and the regulation of these behaviours. Also, the present findings support the compatible use of Identity Theory and Social Cognitive Theory in the investigation of identity and health behaviour.

Abstract Background: The process that involves the migration of the nucleus pulposus from the innermost annular layers and culminates with the final extrusion of the nucleus has been limited to a few studies. This investigation was directed towards a better understanding of the herniation process. The architecture of the annulus fibrosus and the mechanism of progressive disc herniation were analyzed, using a controlled porcine model. Microscopic and histochemical techniques were employed. <br /><br /> Methodology: Two studies were performed. In the first stage, the macroscopic and microscopic structures of twelve cervical intervertebral discs were compared with young human disc data from studies reported in the literature. Important structural features were studied such as annulus fibrosus thickness, number of lamellae, lamellae thickness, orientation of the lamellae fibers and blood supply. In the second study, sixteen fresh-frozen functional spine units were submitted to repetitive flexion?extension motions combined with a low compressive load in a servo-hydraulic dynamic testing system. Discograms, dissections and histochemical techniques were applied to characterize the cumulative damage. The experiment produced eight complete herniations, four partial herniations and four specimens without any microscopic detectable annular damage. <br /><br /> Results and Discussion: The structure of the cervical porcine disc resembles the lumbar human disc. Some differences are evident. The size of the annulus is smaller, the thickness of the lamellae is narrower and the number of layers is fewer in the pig. It is hypothesized that the flexion-extension motion combined with a low-level load produced an increased hydraulic pressure in the inner wall of the posterior annulus. This pressure and repetitive motion first produced a small cleft, spreading the collagen bundles inside the first layer. The nuclear material was "pumped" through the small cleft to the first layer filling the layer creating a fluid-filled pocket between the collagen fibers. Once the "pocket" acquired enough pressure a new cleft was produced in the weakest part of the layer allowing the nuclear material to create a new "pocket" in the second layer. This was the first stage of damage and disc herniation production. This mechanism was repeated until the nucleus traveled along the annulus reaching the posterior longitudinal ligament. At this point a complete extrusion herniation was produced. <br /><br /> Conclusion: The porcine model appears to be suitable as a model to understand the mechanism of disc herniation when the spine is subjected to flexion-extension motions combined with a low-level load. The first cumulative injury appears to be a cleft between the lamellae bundles produced by the nuclear hydraulic pressure. A cumulative load/cumulative injury model approach was used to create the damage that was quantified in the study.

Gloved work has been shown to increase the effort required to perform manual tasks. In power grip tasks, these differences have been observed as reductions in strength and increases in muscular effort. Decreases in force output have been attributed to a number of factors, including loss of tactile sensitivity, glove flexibility or suppleness, thickness, changes in hand geometry, and friction at the glove-object interface. Glove research has rarely quantified glove attributes, and often compared gloves of varying material and physical properties. This research had the unique opportunity to control for a number of these properties by using three sets of identical gloves (powerline maintainers? insulating rubber gloves), differing only in thickness. <br /><br /> Administering the Von Frey Hair Test indicated that the gloves did indeed decrease tactile sensitivity. This research showed that increasing glove thickness led to large decreases in maximum power grip force. Small changes in hand geometry, such as increased interdigital space or grip span, affected force output. In the same hand posture, participants increased their grip force with increasing glove thickness for the object lifting task but were able to maintain a fixed submaximal force with visual feedback. The decrease in tactile sensitivity is a likely cause of this difference. <br /><br /> Muscular activity was affected by wearing the gloves while performing manual tasks. Inconsistent responses of muscular activation were seen in gloved maximum grip effort, while overall increases in electromyographic activity were recorded for tasks at submaximal levels when wearing gloves. <br /><br /> Interdigital spacing had different effects on maximal and submaximal tasks. For maximum effort power grip, interdigital spacing decreased force output by as much as 10%, with no significant changes in muscle activation. For submaximal tasks, no significant differences were seen in muscular activity or in force output. The overall force capability of the gloved user is hindered by changes in interdigital spacing at near maximal effort, but does not appear to be for tasks requiring lower grip force, such as the lifting task which required roughly 20%MVC. Overall, the effect of wearing these gloves on the users, the powerline maintainers, is a substantially increased effort to work. This research contributes to a greater understanding of why and how gloves inhibit performance.

Why are people unable to adhere to an exercise program? Adhering to an exercise program is complex, and exercisers struggle with a variety of challenges that require self-regulation (e. g. , making time, learning skills, changing behaviour). Bandura (1995b) has deemed the assessment of self-regulatory efficacy to manage the regular performance of health behaviours (e. g. , exercise) essential. Despite this recommendation, few components of self-regulation have been examined in the exercise and self-efficacy research to date (McAuley & Mihalko, 1998). Furthermore, major reviews of the exercise-related self-efficacy literature have demonstrated that task self-efficacy has been the predominant operationalization of the self-efficacy construct, and barriers self-efficacy has been the most prevalent operationalization of self-regulatory efficacy (Culos-Reed, Gyurcsik, & Brawley, 2001; McAuley & Mihalko, 1998). However, self-regulation of behaviour involves more than managing barriers and overcoming their limitations (Barone, Maddux, & Snyder, 1997; Brawley, 2005; DuCharme & Brawley, 1995). In order to examine other aspects of self-regulatory efficacy, self-efficacy theory was used as the underpinning for the three studies in this dissertation (Bandura, 1986, 1997). <br /><br /> In Study One an expanded operationalization of exercise-related self-regulatory efficacy was investigated. The construction of various self-regulatory efficacy indices was informed by self-regulation frameworks (Barone et al. , 1997; Baumeister et al. , 1994). These indices as well as barriers efficacy were used to prospectively predict self-reported exercise behaviour. The hierarchical multiple regression analysis indicated that the expanded self-regulatory efficacy variables (i. e. , scheduling, relapse prevention, goal-setting self-efficacy) explained a significant amount of variance in exercise behaviour. In addition, barriers efficacy also contributed significant, but modest, variance to the model. These results underscore McAuley and Mihalko?s (1998) recommendation that multiple measures of self-efficacy should be used to examine exercise behaviour. The findings also emphasize that a focus solely on barriers as the indicant of self-regulatory efficacy in exercise may be overlooking other aspects of the construct that contribute to prediction. <br /><br /> Study Two extended the descriptive findings of the first study and addressed a recognized research need (Dzewaltowski, 1994; McAuley & Blissmer, 2000; McAuley et al. , 2001). Specifically, this study examined the possibility of individual differences (i. e. , optimism, consideration of future consequences) influencing the relationship between self-regulatory efficacy and exercise behaviour. Results indicated that participants higher in optimism reported significantly greater self-regulatory efficacy and exercise intentions for intensity than did those lower in optimism. In addition, participants higher in consideration of future consequences (CFC) reported greater self-regulatory efficacy and exercise attendance than participants with moderate CFC. Finally, CFC significantly moderated the influence of various indices self-regulatory efficacy on subsequent exercise attendance. However the effect upon the prospective relationship was modest. <br /><br /> Whereas the first two studies examined the predictive relationship between self-regulatory efficacy and exercise behaviour, Study Three focused upon the influence of sources of self-regulatory efficacy in strengthening efficacy beliefs. This investigation concerned the effects of an acute manipulation of self-efficacy information in changing self-regulatory self-efficacy within a special population -- cardiac rehabilitation exercise program participants. According to theory, sources of self-efficacy information are common to task and self-regulatory efficacy (Bandura, 1997). <br /><br /> The study used a 2 (message condition) by 2 (time) design in which cardiac rehabilitation program participants were randomly assigned to conditions. Utilizing a written message employing the self-efficacy sources of verbal persuasion and vicarious experiences, self-regulatory efficacy for the scheduling of <em>independent</em> exercise was targeted within an ?efficacy enhancing? condition. This condition was compared to an ?information control? message of other information relevant to cardiac rehabilitation participants. As hypothesized, the efficacy-enhancing condition exhibited increased scheduling self-efficacy compared to the control condition. As well, exercise-related cognitions (i. e. , intentions for frequency, action plans, behavioural commitment to learning about independent exercise) were superior for the efficacy-enhancing condition participants compared to their control conditioncounterparts. <br /><br /> Taken together, the studies support and extend research on self-regulatory efficacy in the exercise domain. In part, this was accomplished by expanding the operationalization of exercise-related self-regulatory efficacy to represent more components of self-regulation than examined in the exercise literature to date. In addition, these studies extend previous descriptive research by examining the potential moderators of the influence of self-regulatory efficacy on exercise behaviour. Finally, the third study represented one of the first efforts to experimentally manipulate determinants of self-regulatory efficacy for independent exercise in a special population. It supported the hypothesis that informational determinants (i. e. , vicarious experience, verbal persuasion) can be acutely manipulated to increase self-regulatory efficacy among cardiac rehabilitation participants.

Undesirable landing area (e. g. , a hole, a fragment of glass, a water puddle, etc) creates the necessity for an alternate foot placement planning and execution. Previous study has proposed that three determinants are used by the central nervous system (CNS) for planning an alternate foot placement: minimum foot displacement, stability and maintenance of forward progression. However, validation of these determinants is lacking. Therefore, the general purpose of the series of studies presented here is to validate and test the generality of the decision algorithm of alternate foot placement selection developed previously. The first study was designed to validate the use of a virtual planar obstacle paradigm and the economy assumption behind minimum foot displacement determinant. Participants performed two blocks of trials. In one block, they were instructed to avoid stepping in a virtual planar obstacle projected in the screen of a LCD monitor embedded in the ground. In another block, they were instructed to avoid stepping in a real hole present in walkway. Behavioral response was unaffected by the presence of a real hole. In addition, it was suggested that minimum foot displacement results in minimum changes in EMG activity which validates the economy determinant. The second study was proposed to validate the stability determinant. Participants performed an avoidance task under two conditions: free and forced. In the free condition participants freely chose where to land in order to avoid stepping in a virtual obstacle. In the forced condition, a green arrow was projected over the obstacle indicating the direction of the alternate foot placement. The data from the free condition was used to determine the preferred alternate foot placement whereas the data from the forced condition was used to assess whole body stability. It was found that long and lateral foot placements are preferred because they result in a more stable behavior. The third study was designed to validate the alternate foot placement model in a more complex terrain. Participants were required to avoid stepping in two virtual planar obstacles placed in sequence. It was found that participants used the strategy of planning the avoidance movement globally and additional determinants were used. One of the additional determinants was implementation feasibility. In the third study, gaze behavior was also monitored and two behaviors emerged from this data. One sub-group of participants fixated on the area stepped during adaptive step, whereas another sub-group anchor their gaze in a spot ahead of the area-to-be avoided and used peripheral vision for controlling foot landing. In summary, this thesis validates the three determinants for the alternate foot placement planning model and extends the previous model to more complex terrains.

In developing a method of quantifying stability in the lumbar spine Cholewicki and McGill (1996) have also broached the notion of sufficient stability, where too much stiffness (and stability) would hinder motion. Thus people highly skilled at maintaining stability may use different and optimal strategies, where <i>sufficient</i> stability is maintained. The purpose of this work was to explore the contributors to <i>sufficient</i> stability, how they coordinate and relate to injury mechanisms. This work represents a cascade of investigations where. 1) To explore the balance of various sources of stiffness and their effect on the critical load and post-buckling behaviour, simulations were undertaken where the buckled configuration of the spine was predicted and its stability in this new configuration was assessed. 2) The various sources of stiffness contributing to stability in the lumbar spine have been in some cases found to be deficient. The question of how these deficiencies place individuals at risk of instability, if at all, remains unresolved. A challenged breathing task was used to determine if there was a difference in stabilizing potential between healthy individuals and low back pain sufferers. Given that differences in stabilizing potential are apparent, several tasks which included a predetermined motor strategy, such as 3)pressurizing the abdomen and 4) abdominal hollowing vs. muscle bracing, were evaluated to determine if individuals can utilize motor strategies to augment stability. The stabilizing potential of abdominal pressure (IAP) and its interaction with muscle activation was evaluated. Some individuals are more skilled at stabilizing their lumbar spine than others. Some consciously controlled motor strategies are better stabilizers than others. These strategies highlight the relative contributions of various components (posture, passive tissue, muscle activation, and load) in that no single muscle dominates stability and IAP appears to augment stability beyond muscle activation alone. The margin of safety is considerable and depends on the task at hand, but it is possible to speculate on which tissues are at greatest risk of injury.

This study was designed to test the hypothesis that 60 days continuous head down bed rest (HDBR), an Earth-based analogue of the effects of space flight, would elevate factors that increase vasoconstriction and would increase markers of vascular inflammation. The study incorporated countermeasures consisting of treadmill running within lower-body negative pressure and resistive "flywheel" exercise (exercise countermeasure, EX) or an increased protein intake of 0. 6 g/kg body weight/day (dietary countermeasures, DIET) to determine whether these interventions might prevent the vasoconstrictor and inflammatory responses when compared to a control (CON) group. Markers of vascular health measured in the study include the vasoactive molecules angiotensin II (Ang II), endothelin-1 (ET-1), and nitric oxide metabolites (NO_met); and markers of inflammation including C-reactive protein (CRP), and the adhesion molecules E-selectin (E-sel), intracellular adhesion molecule-1 (ICAM), and vascular cell adhesion molecule-1 (VCAM). Twenty four women were housed at the MEDES clinic in Toulouse, France, as part of a large international study (Women International Space Simulation for Exploration, WISE) in which various experimental protocols and countermeasures were integrated into a single experimental design completed during two campaigns. Each 100 day campaign included 20 days of pre-testing (pre-HDBR), 60 days of bed rest (HDBR), and 20 days of post-testing (post-HDBR). The experimental countermeasures were applied only during the 60-day HDBR period. Following 60 days of HDBR, many changes occurred in the concentrations of the measured molecules. Specifically, the concentration of Ang II significantly increased in the CON and DIET groups (52. 9%, p = 0. 014; and 124. 4%, p <0. 0001 respectively), but not in the EX group. Also, NO_met decreased in all groups, with reductions in the EX and DIET groups (p = 0. 013, and p = 0. 056 respectively). Markers used to assess vascular inflammation increased following the HDBR. The increase in CRP in the CON and DIET groups and the decrease in the EX group from pre- to post-HDBR were not significant; however, the directional changes resulted in an interaction between group and HDBR (p = 0. 052). The adhesion molecule E-sel was significantly increased in the DIET group (p = 0. 003), and VCAM was significantly increased in the CON group (p = 0. 016) with a smaller increase in the DIET group (p = 0. 08). No changes in adhesion molecules were observed in the EX group. This study demonstrated that 60 days of HDBR by young, healthy, women caused changes in several different molecules that are beginning to emerge as risk factors for the development of cardiovascular diseases. Further, it was observed that regular, vigorous exercise during HDBR prevented these changes. These results suggest that future studies of this kind should directly monitor the effects of simulated space flight on vascular health in men and women to obtain a greater understanding of the adaptations that might occur during long term space exploration missions. HDBR can be considered an extreme model of physical inactivity and could be used to provide insight into mechanisms of disease processes associated with the sedentary lifestyle that is prevalent in Western society.

Walking around in dynamically changing environments require the integration of three of our sensory systems: visual, vestibular, and kinesethic. Vision is the only modality of these three sensory systems that provides information at a distance for proactively controlling locomotion (Gibson, 1958). The visual system provides information about self-motion, about body position and body segments relative to one another and the environment, and environmental information at a distance (Patla, 1998). Gibson (1979) developed the idea that everyday behaviour is controlled by perception-action coupling between an action and some specific information picked up from the optic flow that is generated by that action. Such that visual perception guides the action required to navigate safely through an environment and the action in turn alters perception. The objective of my thesis was to determine how well perception and action are coupled when approaching and walking through moving doors with dynamically changing apertures. My first two studies were grouped together and here I found that as the level of threat increased, the parameters of control changed and not the controlling mechanism. The two dominant action control parameters observed were a change in approach velocity and a change in posture (i. e. shoulder rotation). These findings add to previous work done in this area using a similar set-up in virtual reality, where after much practice participants increased success rate by decreasing velocity prior to crossing the doors. In my third study I found that visual fixation patterns and action parameters were similar when the location of the aperture was predictable and when it was not. Previous work from other researchers has shown that vision and a subsequent action are tightly coupled with a latency of about 1second. I have found that vision only tightly couples action when a specific action is required and the threat of a collision increases. My findings also point in the same direction as previous work that has shown that individuals look where they are going. My last study was designed to determine if we go where we are looking. Here I found that action does follow vision but is only loosely correlated. The most important and common finding from all the studies is that at 2 seconds prior to crossing the moving doors (any type of movement) vision seems to have the most profound effect on action. At this time variability in action is significantly lower than at prior times. I believe that my findings will help to understand how individuals use vision to modify actions in order to avoid colliding with other people or other moving objects within the environment. And this knowledge will help elderly individuals to be better able to cope with walking in cluttered environments and avoid contacting other objects.

Why are people unable to adhere to an exercise program? Adhering to an exercise program is complex, and exercisers struggle with a variety of challenges that require self-regulation (e. g. , making time, learning skills, changing behaviour). Bandura (1995b) has deemed the assessment of self-regulatory efficacy to manage the regular performance of health behaviours (e. g. , exercise) essential. Despite this recommendation, few components of self-regulation have been examined in the exercise and self-efficacy research to date (McAuley & Mihalko, 1998). Furthermore, major reviews of the exercise-related self-efficacy literature have demonstrated that task self-efficacy has been the predominant operationalization of the self-efficacy construct, and barriers self-efficacy has been the most prevalent operationalization of self-regulatory efficacy (Culos-Reed, Gyurcsik, & Brawley, 2001; McAuley & Mihalko, 1998). However, self-regulation of behaviour involves more than managing barriers and overcoming their limitations (Barone, Maddux, & Snyder, 1997; Brawley, 2005; DuCharme & Brawley, 1995). In order to examine other aspects of self-regulatory efficacy, self-efficacy theory was used as the underpinning for the three studies in this dissertation (Bandura, 1986, 1997). <br /><br /> In Study One an expanded operationalization of exercise-related self-regulatory efficacy was investigated. The construction of various self-regulatory efficacy indices was informed by self-regulation frameworks (Barone et al. , 1997; Baumeister et al. , 1994). These indices as well as barriers efficacy were used to prospectively predict self-reported exercise behaviour. The hierarchical multiple regression analysis indicated that the expanded self-regulatory efficacy variables (i. e. , scheduling, relapse prevention, goal-setting self-efficacy) explained a significant amount of variance in exercise behaviour. In addition, barriers efficacy also contributed significant, but modest, variance to the model. These results underscore McAuley and Mihalko?s (1998) recommendation that multiple measures of self-efficacy should be used to examine exercise behaviour. The findings also emphasize that a focus solely on barriers as the indicant of self-regulatory efficacy in exercise may be overlooking other aspects of the construct that contribute to prediction. <br /><br /> Study Two extended the descriptive findings of the first study and addressed a recognized research need (Dzewaltowski, 1994; McAuley & Blissmer, 2000; McAuley et al. , 2001). Specifically, this study examined the possibility of individual differences (i. e. , optimism, consideration of future consequences) influencing the relationship between self-regulatory efficacy and exercise behaviour. Results indicated that participants higher in optimism reported significantly greater self-regulatory efficacy and exercise intentions for intensity than did those lower in optimism. In addition, participants higher in consideration of future consequences (CFC) reported greater self-regulatory efficacy and exercise attendance than participants with moderate CFC. Finally, CFC significantly moderated the influence of various indices self-regulatory efficacy on subsequent exercise attendance. However the effect upon the prospective relationship was modest. <br /><br /> Whereas the first two studies examined the predictive relationship between self-regulatory efficacy and exercise behaviour, Study Three focused upon the influence of sources of self-regulatory efficacy in strengthening efficacy beliefs. This investigation concerned the effects of an acute manipulation of self-efficacy information in changing self-regulatory self-efficacy within a special population -- cardiac rehabilitation exercise program participants. According to theory, sources of self-efficacy information are common to task and self-regulatory efficacy (Bandura, 1997). <br /><br /> The study used a 2 (message condition) by 2 (time) design in which cardiac rehabilitation program participants were randomly assigned to conditions. Utilizing a written message employing the self-efficacy sources of verbal persuasion and vicarious experiences, self-regulatory efficacy for the scheduling of <em>independent</em> exercise was targeted within an ?efficacy enhancing? condition. This condition was compared to an ?information control? message of other information relevant to cardiac rehabilitation participants. As hypothesized, the efficacy-enhancing condition exhibited increased scheduling self-efficacy compared to the control condition. As well, exercise-related cognitions (i. e. , intentions for frequency, action plans, behavioural commitment to learning about independent exercise) were superior for the efficacy-enhancing condition participants compared to their control conditioncounterparts. <br /><br /> Taken together, the studies support and extend research on self-regulatory efficacy in the exercise domain. In part, this was accomplished by expanding the operationalization of exercise-related self-regulatory efficacy to represent more components of self-regulation than examined in the exercise literature to date. In addition, these studies extend previous descriptive research by examining the potential moderators of the influence of self-regulatory efficacy on exercise behaviour. Finally, the third study represented one of the first efforts to experimentally manipulate determinants of self-regulatory efficacy for independent exercise in a special population. It supported the hypothesis that informational determinants (i. e. , vicarious experience, verbal persuasion) can be acutely manipulated to increase self-regulatory efficacy among cardiac rehabilitation participants.