Abstract
Objective This randomized-controlled pilot trial assesses the effects of a 6-week cognitively engaging exercise intervention (CE-EX) vs. repetitive endurance exercise (R-EX), and a control group (CTRL), before (pre), after (post) the intervention and at a 3-month follow-up, for executive functions (EF) in a sample of young adults ( N = 46, m age = 23.76 ± 3.26 years). Methods We performed a linear mixed model with the timepoint × group interaction and participant (ID) as random effect and EF as outcome. Since the completion rate of the intervention was low (CE-EX: 58.33%, R‑EX: 36.26%), we further performed a sensitivity analysis differentiating between those who received the intended dose (completers) of the intervention and those who did not (noncompleters). Results In the primary analysis, we did not find a significant interaction effect. In the sensitivity analysis, the linear mixed model resulted in significant interaction effect of timepoint × group × intervention-completion (Chi 2 (2) = 15.16, p = 0.001). In the post hoc tests, due to Bonferroni correction and a small sample size, there was no significant difference within or between groups in the post hoc tests. Regarding our main hypothesis of changes in EF between groups, we descriptively report a larger change towards better EF for CE-EX completers from pre- to postassessment than in R‑EX completers with small to moderate effects (| d | = 0.37). Conclusion Our results imply that intervention adherence plays a crucial role to obtain the desired positive intervention effects of exercise-inherent cognitive engagement for EF. These results should be verified in a larger study, which focuses on improving intervention adherence.