高強度間欠性トレーニング（HIIT）中の脳酸素化と疼痛認識におけるアスリートと非アスリートの違い：機能的近赤外分光法による解明

Regular physical activity is an important treatment component for chronic pain. To unravel the neuronal influence of exercise on pain, we investigated the neuronal changes during exercise-induced hypoalgesia in endurance athletes and controls. Twenty-two athletes (mean age: 33.3 ± 10.8 years) and 20 non-athletes (mean age: 28.9 ± 9.0 years) underwent high-intensity interval training (HIIT) and pressure pain tests, while brain oxygenation was monitored using functional near-infrared spectroscopy to cover key regions of pain processing: the prefrontal cortex (PFC), sensorimotor cortices and posterior parietal cortex (PPC). During HIIT both groups exhibited a steady increase in PFC oxyhaemoglobin, with athletes showing a greater increase in the PPC area than non-athletes. As expected athletes showed a significant reduction in pain perception after HIIT, whereas non-athletes did not. In line with this athletes showed a significant decrease in oxyhaemoglobin levels in all brain areas post-HIIT, whereas non-athletes only showed a decrease in sensorimotor areas. Interestingly, in athletes, pain reduction correlated with the decrease in PFC oxyhaemoglobin during painful stimulation, whereas no significant correlation was observed in non-athletes. The pronounced HIIT-induced increase in oxyhaemoglobin in athletes may elevate baseline neural activity to a level where additional activation is limited, potentially reducing the salience of pain-related signals. This athlete-specific response may result from endurance training adaptations, such as enhanced microvascularization and oxygen delivery, promoting greater neural efficiency during high-intensity exercise. These findings highlight HIIT's potential as a targeted pain management strategy for athletes and the need for tailored approaches in non-athletes. KEY POINTS: Regular physical activity is known to reduce pain, but the brain mechanisms behind this effect are not well understood, especially in trained compared with untrained people. We studied how the brain responds to short bouts of very intense exercise and how this relates to pain perception in endurance athletes and non-athletes. During exercise athletes showed a stronger increase in oxygen supply in brain regions involved in attention and body awareness than non-athletes. Only athletes experienced reduced pain after exercise, which was linked to lower activity in the frontal brain regions during painful stimulation. These results suggest that long-term endurance training changes how the brain processes pain during and after exercise, which may help design more effective exercise-based pain treatments for different populations.