Comparison of Acute Irisin and Cognitive Responses to Different Exercise Modalities Among Late Adolescents

Background/Objectives: Exercise supports physical and cognitive health through neurotrophin-mediated pathways, with irisin playing a key role in neuroprotection and synaptic plasticity. As adolescence represents a period of heightened neuroplasticity and metabolic adaptation, determining how different exercise modalities influence neurotrophic and cognitive responses is critical for health promotion in youth. This study aimed to compare the acute effects of low-intensity continuous training (LICT), short-interval high-intensity interval training (SI-HIIT), and long-interval HIIT (LI-HIIT) on circulating irisin levels and executive function in healthy late adolescent males. Methods: Eleven participants completed all conditions in a randomized crossover design with a 7-day washout. Venous blood samples and the Trail-Making Test, Parts A and B (TMT-A, TMT-B) were assessed pre- and postexercise, with continuous heart rate monitoring. Results: Post-exercise irisin levels were significantly greater in both HIIT protocols (SI-HIIT, p < 0.001; LI-HIIT, p < 0.038) than in the LICT protocol. Only the SI-HIIT group presented significantly shorter TMT-A (vs. LICT, p < 0.001; vs. LI-HIIT, p = 0.016) and TMT-B (vs. LICT, p < 0.001; vs. LI-HIIT, p < 0.001) completion times post-exercise. Conclusions: A single HIIT session elicited greater increases in circulating irisin and executive function compared with LICT. These findings highlight exercise intensity and interval structure as key factors for enhancing neurocognitive health, offering valuable insight for developing early-life training strategies to promote brain health.