Motivation for physical activity and the moderating effect of cancer diagnosis: A nationally representative cross-sectional study.

The aim of this study was to investigate associations between types of motivation for physical activity and self-reported weekly aerobic moderate-to-vigorous physical activity (MVPA) in the 2012 and 2014 waves of the nationally representative Health Information National Trends Survey 4 (n = 7307). We further explored differential associations between MVPA and types of motivation for physical activity by cancer survivor status. We found that those who were more motivated by "getting enjoyment from exercise" reported 26.4% more MVPA (+49.8 min/week) than those who were less motivated by this factor, adjusting for covariates (p = 0.025). Conversely, those who were more motivated by "concern over the way you look" reported 22.1% less MVPA (-55.5 min/week) than those who were less motivated by this factor, adjusting for covariates (p = 0.002). We found no evidence for a relationship between motivation from either "pressure from others" or "feeling guilty when you skip exercising" and MVPA. We identified a significant interaction for "feeling guilty when you skip exercising" and cancer survivor status, adjusting for covariates (p = 0.034). Cancer survivors who reported being more motivated by "feeling guilty when you skip exercising" reported 36.2% less MVPA (-71.75 min/week) than those who were less motivated by this factor; there was no statistically reliable difference in those without a history of cancer. Findings are concordant with previous literature highlighting the primacy of enjoyment for physical activity adherence. There is a need for further inquiry into guilt-related motivation for physical activity among cancer survivors, as it may have a unique, negative impact in this population.