Comparing positive versus negative intrinsic rewards for predicting physical activity habit strength and frequency during a period of high stress.

The experience of positive intrinsic rewards (enjoyment) from physical activity (PA) is known to promote PA habit formation and maintenance. Negative intrinsic rewards (stress reduction) may also be associated with PA habit, particularly during a major stressor and when individual-level anxiety is higher. Multi-level models tested the following hypotheses using weekly survey data from a convenience sample (snowball sampling) of adults (N = 580; 91% White, 77% Female, mean age = 41 years) over the 8 weeks of the first COVID-19 lockdown in the UK: negative intrinsic rewards will be independently and statistically more strongly related to PA habit strength and frequency than positive intrinsic rewards; and, the relationship between negative intrinsic rewards and PA habit strength and frequency will be stronger for those with higher anxiety. Counter to the hypotheses, positive intrinsic rewards were more strongly associated with PA habit strength over time than negative intrinsic rewards (fixed effect = 0.27, p < 0.001 versus fixed effect = -0.05, p = 0.23, respectively), and there was a main effect of anxiety (but no interaction with negative rewards) on PA habit strength (fixed effect = -0.03, p = 0.03). The findings suggest that interventions aimed at increasing and maintaining PA habit strength might best focus on cultivating positive intrinsic rewards (enjoyment) from PA, even in the presence of substantial stressors and individual-level anxiety.