High-intensity interval and moderate-intensity continuous training on cerebral energy metabolism in older rats

Aging is associated with metabolic decline in the brain, increasing susceptibility to neurodegenerative diseases. While exercise is a well-established strategy to counteract these changes, no study has directly compared the effects of moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) on cortical and hippocampal energy metabolism-key regulators of brain plasticity in aging. To address this gap, we investigated how 4-week MICT and HIIT protocols, structured according to the lactate threshold, affect endurance performance and brain metabolic markers in older Wistar rats. Both training modalities improved endurance, with HIIT demonstrating superior gains in maximal performance. However, molecular analyses revealed that MICT induced more extensive metabolic and angiogenic adaptations in the cortex and hippocampus, including the upregulation of key regulators of energy metabolism and vascularization. RNA sequencing confirmed broader transcriptomic changes following MICT, implicating pathways associated with neurogenesis, metabolic homeostasis, and cellular plasticity. While HIIT provided a time-efficient means of improving cardiovascular endurance and mitochondrial activity through different molecular pathways when compared to MICT, its impact on brain metabolism was more limited. These findings suggest that MICT is the preferred regimen for enhancing cerebral metabolic function and neurovascular adaptation, while HIIT serves as a complementary strategy to involve other brain metabolism-associated pathways and maximize aerobic fitness. A direct comparison of these modalities, as presented here, is essential for refining exercise prescriptions to support brain health in aging.