Examining the Between- and Within-Person Associations Between Psychological Stress and Physical Activity: A Random...

Physical activity is well-evidenced to reduce stress and health risks. Frequent or prolonged psychological stress increases the risk for physical and mental health morbidities. Further, high stress may also impair physical activity behaviours. Eight hundred adults (M_age = 41.47, SD = 13.61; % women = 47.5%) completed questionnaires at baseline, as well as one- and two-month follow-ups that were used to measure physical activity and psychological stress. A random intercept cross-lagged panel model was fit to explore the bidirectional, month-to-month associations between physical activity and psychological stress. There were significant between-person associations between psychological stress and physical activity (r = -0.209, SE = 0.050, 95% CI = [-0.307, -0.110]). The within-person associations between physical activity and subsequent psychological stress (b = -0.069, SE = 0.048, 95% CI = [-0.162, 0.024]) as well as stress and subsequent physical activity (b = -0.094, SE = 0.105, 95% CI = [-0.301, 0.112]) were non-significant, but medium-to-large ( ${\beta }_{1\to 2}$  = -0.114, ${\beta }_{2\to 3}$  = -0.111) and small-to-medium ( ${\beta }_{1\to 2}$  = -0.065, ${\beta }_{2\to 3}$ -0.057) in magnitude, respectively. Our findings demonstrate that, on average, individuals participating in greater levels of physical activity report lower stress. Further research is needed to explore the discrepancy between the significant between-person effects and the non-significant within-person cross-lagged effects.