Impact of a 12-week high-intensity interval training program on working memory in young adults with overweight or obesity

Objective: To examine the association of a 12-week high-intensity interval training (HIIT) program with working-memory performance in young adults aged 18–25 years with overweight or obesity.

Methods: A total of 120 young adults with overweight or obesity were randomly allocated to an HIIT group ( n = 48) or a control group ( n = 72). The HIIT group completed a 12-week structured program, whereas the control group maintained usual daily activities. Working-memory updating was assessed using 1-back and 2-back tasks. Post-test body weight and maximal oxygen consumption (VO 2 max) were analysed using baseline-adjusted analysis of covariance (ANCOVA), whereas body mass index (BMI) was analysed using repeated-measures ANCOVA. Reaction-time outcomes were analysed using a 2 × 2 × 2 mixed repeated-measures ANCOVA, with group as the between-subject factor and time and cognitive load as within-subject factors. Because marked baseline imbalance was observed for accuracy, 1-back and 2-back accuracy were analysed separately using baseline-adjusted post-test ANCOVA. Exploratory partial correlation analyses examined associations between changes in VO 2 max and n-back performance separately within the HIIT and control groups. An additional exploratory linear regression model tested whether the association between VO 2 max improvement and 2-back reaction-time improvement differed between groups.

Results: Baseline-adjusted ANCOVA showed lower post-test body weight in the HIIT group than in the control group [ F (1,115) = 110.07, p < 0.001, η 2 = 0.256] and higher post-test VO 2 max [ F (1,115) = 300.86, p < 0.001, η 2 = 0.451]. Repeated-measures ANCOVA showed a significant group × time interaction for BMI [ F (1,115) = 137.60, p < 0.001, η 2 = 0.545]. For reaction time, the 2 × 2 × 2 mixed repeated-measures ANCOVA showed a significant group × time interaction [ F (1,115) = 31.95, p < 0.001, partial η 2 = 0.217] and a significant group × cognitive-load interaction [ F (1,115) = 9.22, p = 0.003, partial η 2 = 0.074], whereas the group × time × cognitive-load interaction was not significant [ F (1,115) = 2.15, p = 0.145, partial η 2 = 0.018]. After adjustment for baseline accuracy and other measured baseline covariates, no significant post-test group difference was observed in 1-back accuracy [ F (1,114) = 0.91, p = 0.343] or 2-back accuracy [ F (1,114) = 2.17, p = 0.143]. In exploratory analyses, VO 2 max improvement was associated with 2-back reaction-time improvement in the HIIT group ( r = 0.391, p = 0.009) but not in the control group ( r = −0.101, p = 0.411). However, the group × VO 2 max-improvement interaction did not reach conventional statistical

Significance: (β = 388.57, 95% CI: −7.68 to 784.82, p = 0.055).

Conclusion: Participation in the 12-week HIIT program was associated with lower adjusted post-test body weight, higher adjusted post-test VO 2 max, a greater reduction in BMI, and more favorable reaction-time performance averaged across n-back loads. No adjusted post-test between-group difference in accuracy was observed. The non-significant group × time × cognitive-load interaction does not support a cognitive-load-specific effect. Although the VO 2 max–2-back reaction-time association was observed in the HIIT group but not in the control group, the non-significant interaction model did not conclusively establish training specificity. Dietary intake, habitual physical activity, sedentary behavior, complete individual-level exercise intensity, and formal assessor blinding were not available; therefore, the observed differences cannot be attributed exclusively to HIIT.