A brief intervention to increase physical activity behavior among adolescents using mental simulations and action planning

Abstract

This study evaluated the effectiveness of a brief integrated theory-based intervention to increase physical activity (PA) among adolescents over a three-month follow-up period. A 2 (mental simulation: present vs. absent) × 2 (action planning: present vs. absent) × 4 (time: baseline vs. one-month vs. two-month vs. three-month follow-up) mixed-model randomized controlled design was adopted. Adolescents aged 14–15 years (N = 267) completed baseline psychological measures and self-reported PA followed by the relevant intervention manipulation, if appropriate, with follow-up measures collected one, two, and three months later. Results revealed no significant effects for the mental simulation and action planning strategies nor the interaction of the two strategies. However, among participants with low levels of baseline PA, participants in both mental simulation alone and action planning alone groups reported significantly higher levels of PA at one-month follow up than other groups, suggesting that individual intervention components may be effective in low-active adolescents.

Keywords:

• Adolescents
• action planning
• outcome mental simulation
• physical activity
• randomized controlled trial

Acknowledgement

We thank Elina Ernits, Epp Hoovi, and Roomet Viira for their assistance with the data collection for this study.

Notes

1. Sample sizes were 71 for low PA sub-group (control, n = 18; action planning only, n = 13; mental simulation only, n = 17; combined, n = 23) and 80 for high PA sub-group (control, n = 19; action planning only, n = 17; mental simulation, n = 21; combined action, n = 23).

2. We specified the following contrasts. First, for the between-participant factor ’intervention condition’, two sets of contrasts were specified. The first contrast tested the efficacy of the action planning only, mental simulation only, and combined condition relative to the control condition by using 1, 1, 1, and −3 weights, respectively. The second contrast compared the action planning only and mental simulation only with the combined condition (by using 1, 1, −2, and 0). Second, for the within-participant factor ‘time’, three sets of contrasts were specified. Specifically, the baseline was used as a reference category and was compared with the one-, two, and three-month follow-up, respectively.