Does Stress Result in You Exercising Less? Or Does Exercising Result in You Being Less Stressed? Or Is It Both? Testing the Bi-directional Stress-Exercise Association at the Group and Person (N of 1) Level

Abstract

Background: Psychosocial stress contributes to heart disease in part by adversely affecting maintenance of health behaviors, while exercise can reduce stress. Assessing the bi-directional relationship between stress and exercise has been limited by lack of real-time data and theoretical and statistical models. This lack may hinder efforts to promote exercise maintenance.

Purpose: We test the bi-directional relationship between stress and exercise using real-time data for the average person and the variability-individual differences-in this relationship.

Methods: An observational study was conducted within a single cohort randomized controlled experiment. Healthy young adults, (n = 79) who reported only intermittent exercise, completed 12 months of stress monitoring by ecological momentary assessment (at the beginning of, end of, and during the day) and continuous activity monitoring by Fitbit. A random coefficients linear mixed model was used to predict end-of-day stress from the occurrence/non-occurrence of exercise that day; a logistic mixed model was used to predict the occurrence/non-occurrence of exercise from ratings of anticipated stress. Separate regression analyses were also performed for each participant. Sensitivity analysis tested all models, restricted to the first 180 days of observation (prior to randomization).

Results: We found a significant average inverse (i.e., negative) effect of exercise on stress and of stress on exercise. There was significant between-person variability. Of N = 69, exercise was associated with a stress reduction for 15, a stress increase for 2, and no change for the remainder. We also found that an increase in anticipated stress reported the previous night or that morning was associated with a significant 20-22% decrease (OR = 0.78-0.80) in the odds of exercising that day. Of N = 69, this increase in stress reduced the likelihood of exercise for 17, increased the odds for 1, and had no effect for the remainder. We were unable to identify psychosocial factors that moderate the individual differences in these effects.

Conclusions: The relationship of stress to exercise can be uni- or bi-directional and varies from person to person. A precision medicine approach may improve exercise uptake.

Keywords: Exercise; Stress.

Figure 1

Consort Diagram

Figure 2. Forest plot of change in stress on days with less than 30 minutes of moderate or vigorous physical activity

Forest Plot showing the effect of a continuous 30-minute or greater bout of continuous moderate to vigorous physical activity on the evening stress report that day, for up to 365 days (Effect size with 95% confidence interval for each participant; black vertical line represents “no association”; red vertical line shows average effect across participants).

Figure 3. Odds ratios for greater than 30 minutes of moderate or vigorous physical activity based on expected AM stress

Forest plot showing the effect of morning report of anticipated stress for that day on the occurrence of a continuous 30-minute or greater bout of continuous moderate to vigorous physical activity that day, for up to 365 days (odds ratio [OR] with 95% confidence interval for each participant; black vertical line represents “no association [OR=1.0]”; red vertical line shows average effect across participants).