Background. Many breast cancer survivors do not meet guidelines for moderate-vigorous physical activity (MVPA), contributing to worse survivorship outcomes. Daily shifts in non-conscious, reflexive processing constructs may explain intention-behavior discordance but have rarely been considered as treatment moderators. This study predicted daily within-person shifts in two reflexive processing constructs, incidental affect (how good-bad one feels, unrelated to a target behavior) and exercise dread (automatic aversion towards exercise), would each moderate the strength of association between daily shifts in exercise intentions and MVPA.
Method. Data were collected for a single-arm trial (NCT04903249) with N = 36 inactive stage 0-III breast cancer survivors within 5 years of completing primary treatment. All participants received an exercise prescription and Fitbit. Ecological momentary assessment (EMA) was used to measure intentions (I intend to spend time exercising today; 1 = “disagree” to 7 = “strongly agree”), incidental affect (How good or bad do you feel right now? 0 = “very bad” to 10 = “very good”), and dread (When I think about exercising today, I experience a sense of dread; 1 = “disagree” to 7 = “strongly agree”) three times daily for 10 consecutive days in four measurement bursts over 12-weeks. ActiGraph wGT3X-BT accelerometers were used to measure total daily MVPA. Linear mixed effects models fit daily MVPA (log transformed) on each construct disaggregated into between and within person effects. Models adjusted for average levels of each construct, ActiGraph wear time, age, BMI, and time since completing treatment.
Results. More daily MVPA was associated with positive shifts in daily exercise intentions (β = 12.95%, 95% CI = 9.56, 16.53, p < 0.001) and daily incidental affect (β = 11.39%, 95% CI = 7.26, 15.62, p < 0.001). Reduced daily MVPA was associated with increases in exercise dread (β = -12.51%, 95% CI = -16.43, -8.44, p < 0.001). Interaction models showed dread attenuated the positive impact of daily exercise intentions on MVPA (β = -5.14%, 95% CI = -8.32, -1.83, p = 0.003), while incidental affect amplified it (β = 2.68%, 95% CI = 0.36, 5.13, p = 0.03).
Conclusions. Both incidental affect and exercise dread moderated the relationship between exercise intentions and MVPA in opposing directions. Future work should consider techniques for boosting incidental affect and reducing exercise dread as well as strengthening exercise intentions.