Table 1.

Constructs and Measures

Construct	Measure
Primary Outcome
Participation in Physical Activity	Self-report using an adapted version of Godin and Shephard's 'Leisure Time Exercise Questionnaire' [32]
Secondary Outcomes
Objective Physical Functioning	Resting heart rate, blood pressure, limb girth circumferences, 6 minute walk, sit to stand (30 seconds), 1 repetition maximum strength test, and Apley's shoulder test [43].
Accelerometer measure	The Actigraph GT3X accelerometer is a small matchbox-sized unit worn on a belt on the hip that is a valid and reliable tool for measuring physical activity among adults [45,46], and will be worn for eight consecutive days, before the intervention commences and during the final week of the intervention.
Quality of Life	European Organization for Research and Treatment of Cancer core quality of life questionnaire (EORTC QLQ-C30, version 3 [35]) and the prostate tumour-specific module (EORTC QLQ-PR25 [36]).
Anxiety	Memorial Anxiety Scale for Prostate Cancer (MAX-PC) [37]
Depression	Centre for Epidemiological Studies Depression Inventory (CES-D) [40].
Mediators
Task Self-Efficacy	Participants rate the certainty with which they believe they can perform three physical tasks. For each task, they rate the certainty with which they believe they can perform these tasks for three time durations: 10, 20, and 30 minutes. Confidence will be measured on an 11-point Likert scale, from 0 (not at all confident) to 100 (extremely confident). Measure based on exercise and cancer research in which task self-efficacy was measured [48].
Barrier Self-Efficacy	Participants rate the certainty with which they believe they can perform exercise when faced with specific barriers. Items (barriers) from Bandura's [47] self-efficacy to regulate exercise instrument, with supplementary items from research on barriers to physical activity for prostate cancer survivors [8] and research on barrier self efficacy and cancer survivors [48]. The 11-point Likert scale used in the measurement of task self-efficacy will also be used to assess barrier self-efficacy.
Outcome Expectations	Multidimensional Outcome Expectations for Exercise Scale (MOEES) [49].
Goals	Participants indicate the number of days per week they intend to perform at least 30 minutes of exercise at a light, moderate or strenuous intensity now and in 12 weeks. Items adapted from previous research using social cognitive theory constructs [51].
Socio-Cultural Factors (factors facilitating or impeding participation in physical activity)	Participants asked perceptions of frequency with which each facilitator and barrier occurs using a 5-point-Likert scale anchored by 0 (never) and 4 (always). Measure based on guidelines for the development of scales to assess barriers to physical activity for cancer patients [52] and content (i.e., facilitators and impediments) drawn from our prior work with prostate cancer survivors [8].