The Impact of Walking on BDNF as a Biomarker of Neuroplasticity: A Systematic Review.

BACKGROUND/OBJECTIVES: The brain-derived neurotrophic factor (BDNF) is a critical exercise-induced modulator of various neuroplasticity processes, including adult hippocampal neurogenesis. Environmental affordance for physical activity is a novel theory that aims to increase the BDNF through walking or climbing stairs, stimulated by the urban and interior environment. In a systematic review, this paper explores the association between walking, as a structured or free-living form of physical activity, and changes in the BDNF in humans with healthy locomotion. METHOD: A systematic review with a registered protocol, INPLASY2024110093, and following the PRISMA guidelines, includes English-language original research articles on adult and older adult human subjects who are locomotor-healthy, studies on walking as a structured exercise or free-living physical activity that is presented in a non-combined intervention, and must report changes in the BDNF as a dependent variable. The search was conducted using three databases: PubMed, Web of Science, and Scopus, resulting in 21 eligible studies. RESULTS: This systematic review finds that the impact of walking on the BDNF is evidenced, but subject to moderate to high intensities in single bouts. At the same time, the long-term effects are yet to be fully understood, potentially due to the uptake of the BDNF for functional brain improvements, neuroplasticity processes, or muscle repair, instead of an accumulation of the BDNF itself, yet still confirm the important role of the BDNF for neurosustainability. Age and environmental factors such as heat are also found to affect the increase in the BDNF. The narrative synthesis provides elaborate explanations for understanding those complex dynamics before reaching future conclusions on the impact of walking or environmental affordance for physical activity on the changes in the BDNF concentrations. CONCLUSIONS: This systematic review highlights the potential role played by moderate- and high-intensity walking as a lifestyle intervention that can be utilised through the built environment to promote adaptive brain changes, through the sustainable regulation of the BDNF.