DISCUSSION
theory‐based, cancer
CANCER, RECRUITMENT, ADVERSE EFFECTS
While PA is well‐recognized as beneficial for cancer survivors, little research has examined longer‐term PA change and maintenance among YACS. The IMPACT intervention offered a mobile PA intervention to YACS who are at risk for adverse effects from cancer decades following their treatment. Following a 6‐month active intervention, tapered contacts and access to a moderated Facebook group did not result in greater increases in accelerometer‐measured total PA min/week in the intervention group at 12 months relative to a self‐help group. However, change in self‐reported total PA min/week from baseline to 12 months was significantly greater in the intervention versus self‐help group. Among both groups, levels of accelerometer‐ and self‐reported total PA were maintained between 6 and 12 months. Further, both groups improved accelerometer‐measured and self‐reported MVPA over 12 months and maintained improvements from 6 to 12 months. Intervention participants (48%) were more likely to report meeting PA guidelines than self‐help participants (33%) at 12 months. Overall, both digital approaches could be promising for promoting sustained PA participation and long‐term health benefits in YACS, but additional research is needed to identify what strategies work for whom, and under what conditions.The lack of intervention effect on accelerometer‐measured total PA at 12 months is similar to prior studies with cancer survivors, which observed PA improvements in both intervention and control groups, resulting in a lack of effects.Other home or web‐based interventions among survivors have reported significant intervention effects on PA at 12 months, but were based on self‐reported outcomes.At 12 months, there was no intervention effect on accelerometer‐measured MVPA, though intervention participants were more likely to report meeting MVPA guidelines than self‐help participants. The between‐group differences in self‐reported MVPA increases over 12 months approached significance. MVPA increases in the self‐help group were consistent with earlier definitions of contamination in home‐based trials (>60 min/week)For some intervention participants, having continued access to goal setting prompted by text message, a Facebook group with moderated prompts, bimonthly lessons and tailored feedback (i.e., theory‐based intervention components designed to promote behavioral capability, self‐regulation, self‐efficacy, and social support) may have promoted successful PA maintenance from 6 to 12 months. Among cancer survivors, self‐regulatory (e.g., goal setting, self‐monitoring, behavioral feedback)The decline in steps from 6 to 12 months within the intervention group may reflect decreases in light PA, which was also observed in a trial of PA maintenance following an intervention among survivors with activity trackers, group sessions, and a phone call.To our knowledge, this is the first study among YACS to evaluate digital intervention strategies to support PA adoption and maintenance over 12 months. Strengths of the study included the randomized controlled design, nationwide recruitment, remote delivery, strong retention, multiple measures of PA and sedentary behavior, and an active comparison group that facilitated evaluation of the sustained effects of access to digital tools and a Facebook group alone. Findings should also be considered in the context of limitations. The correlation between accelerometer‐ and self‐reported PA was significant but small, indicating bias in self‐reported PA measurement, which is reflected in the differing proportions of YACS meeting PA guidelines by measurement type. Since participants were not blinded to group assignment, intervention participants may have had higher social desirability bias to report higher levels of PA. Intervention participants received tapered contacts in months 7–12, which precluded the examination of intervention effects in the absence of continued contact. Given the relatively homogeneous study sample with respect to race, sex, and education, study findings may not be generalizable more broadly to YACS. Finally, the study focused on promotion of aerobic activity without emphasis on strength training, which is another component of the PA guidelines for cancer survivors.This study contributes to the growing evidence that mHealth interventions with activity trackers may be effective for promoting and maintaining PA among cancer survivors. Findings suggest that a theory‐based intervention designed to enhance strategies offered by digital tools was more effective than a self‐help group at 12 months for self‐reported total PA and possibly self‐reported MVPA, but not accelerometer‐measured total PA or MVPA. Overall, both digital approaches have potential for dissemination to widely reach and promote PA maintenance and related health benefits among YACS. Additional research is needed to elucidate for whom, and under what contexts, specific intervention strategies work best.