Acute high-intensity interval training, but not reduced-exertion high-intensity interval training increase brain-derived neurotrophic factor in a block randomized controlled trial

Exercise has been linked to various physical and mental health benefits with neuroplasticity being one of the potential pathways. Brain-derived neurotrophic factor (BDNF) has emerged as one of the most researched factors relating to exercise induced neuroplasticity. As exercise intensity and work to rest ratio differ between various exercise protocols, comparison of high-intensity interval training (HIIT) and reduced exertion high-intensity interval training (REHIT) could indicate a more optimal protocol for neuroplasticity promotion. In this study, 60 low to moderately active young adults took part in a block-randomized clinical trial comparing how acute 15-minute-long HIIT and REHIT affect BDNF and lactate levels, while the control group watched a video. Lactate was measured before and immediately after each intervention in capillary blood, while BDNF was measured in saliva, in the same timeframe. Mixed ANOVA and its nonparametric analogue were used to analyse time, group and time × group interaction effects. Lactate showed a group × time interaction effect, where concentration after exercise reached high concentration in HIIT as well as REHIT, around 9 and 13 mmol/l, respectively, with no change in the control group. BDNF analysis did not show time × group interactions. Median BDNF levels increased significantly by about 25% following HIIT, but no such change was observed in the other groups. Changes in lactate were not related to changes in BDNF in any of the groups. Future studies should test the effectiveness of HIIT in different populations, while exercise induced BDNF changes, as measured in saliva, should be compared to measurements in blood. In sum, the results suggest that an acute 15-minute HIIT can significantly raise BDNF levels in young adults.