The Immediate and sustained benefits of two-week high-frequency aerobic exercise on depressive symptoms and frontal function in subthreshold depression: A randomized controlled trial

Aerobic exercise (AE) has been shown to improve subthreshold depression (SD). Current interventions typically involve longer durations and a moderate frequency. There is potential to further optimize this approach. This study designed a two-week high-frequency AE program and evaluated its efficacy and neural mechanisms in SD. This single-blind, randomized controlled study randomly assigned 57 female SD participants to AE (n = 29; 6-7 sessions/week) or a sitting control (n = 28). Depression severity and symptoms were assessed using the Beck Depression Inventory-II (BDI-II) and the Patient Health Questionnaire-9 (PHQ-9) at baseline, post-intervention, and two-week follow-up. Functional near-infrared spectroscopy combined with the Verbal Fluency Task was used to assess multiple neural activity metrics in the prefrontal cortex and motor cortex. The AE intervention significantly decreased in BDI-II and PHQ-9 scores, while increasing response and remission rates. Simultaneously, AE significantly reduced activation in the dorsolateral prefrontal cortex (DLPFC), frontal eye field (FEF), and premotor and supplementary motor areas (PMC-and-SMA). Functional connectivity strength decreased between the DLPFC and the FEF, PMC-and-SMA, and the primary somatosensory cortex (S1), and the PMC-and-SMA and S1. Network efficiency improved within the S1 and FEF, including enhanced node efficiency, increased degree centrality, and reduced shortest path. Moreover, the functional enhancement of PMC-and-SMA and FEF was significantly associated with alleviations in somatic symptoms (sleep disturbances and fatigue). The study demonstrates the feasibility and efficacy of the two-week high-frequency AE protocol in improving SD, with benefits comparable to those of previous AE protocols.