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Background: Alzheimer’s disease (AD) is the most common and irreversible neurodegenerative disorder, and amyloid peptide plays a central role in its pathogenesis. Physical training contributes as a beneficial adaptation to AD. However, these effects may be underestimated because much of the literature used fixed training prescription variables (intensity and volume) throughout the protocol. Moreover, researchers poorly understand whether chronic high-intensity interval training (HIIT) exerts similar effects on the brain tissue of individuals with AD. Objective: This study evaluated the effect of 8 minutes of HIIT with incremental overload in an AD model. Methods: Forty male Wistar rats were divided into four groups: an untrained Sham group, Sham trained group, Aβ1-42 (Alzheimer’s) untrained group, and Aβ1-42 (Alzheimer’s) trained group (n=10 rats per group). Animals underwent stereotactic surgery and received a hippocampal injection of Aβ1-42 or a saline solution. Seven days after surgery, two weeks of treadmill adaptation followed by a maximal running test (MRT) was performed. Then, animals were subjected to eight weeks of HIIT. Rats were sacrificed 24 h after the behavioral tests (open field and Morris water maze), hippocampal tissue was extracted to analyze the redox balance and BDNF/TrkB pathway, and neuritic plaques (NP) were detected by evaluating silver impregnation. Results: The AD trained group presented a physical capacity amelioration every two weeks and locomotor, learning, and memory improvements (p<0.05). These effects were accompanied by increased CAT and SOD levels, followed by decreased lipid peroxidation (p<0.05). Furthermore, increased activation of the BDNF/TrkB (p<0.05) pathway and decreased NP was observed. Conclusions: Based on these results, MRT was essential for an excellent chronic training protocol prescription and overload adjustment. Therefore, 8 minutes of HIIT daily for 8 weeks may reduce behavioral deficits by promoting a positive redox balance and increased activity of the BDNF/TrkB pathway that may contribute to NP attenuation.

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Background: Alzheimer's disease is the most common neurodegenerative disease in the world, characterized by the progressive loss of neuronal structure and function, whose main histopathological landmark is the accumulation of β-amyloid in the brain. Objective: It is well known that exercise is a neuroprotective factor and that muscles produce and release myokines that exert endocrine effects in inflammation and metabolic dysfunction. Thus, this work intends to establish the relationship between the benefits of exercise through the chronic training of HIIT on cognitive damage induced by the Alzheimer's model by the injection of β amyloid 1-42. Methods: For this purpose, forty-eight male Wistar rats were divided into four groups: Sedentary Sham (SS), Trained Sham (ST), Sedentary Alzheimer’s (AS), and Trained Alzheimer’s (AT). Animals were submitted to stereotactic surgery and received a hippocampal injection of Aβ1-42 or a saline solution. Seven days after surgery, twelve days of treadmill adaptation followed by five maximal running tests (MRT) and fifty-five days of HIIT, rats underwent the Morris water maze test. The animals were then euthanized, and their gastrocnemius muscle tissue was extracted to analyze the Fibronectin type III domain containing 5 (FNDC5), PPARG Coactivator 1 Alpha (PPARGC1A), and Integrin subunit beta 5 (ITGB5-R) expression by qRT-PCR in addition to cross-sectional areas. Results: The HIIT prevents the cognitive deficit induced by the infusion of amyloid β 1-42 (p<0.0001), causes adaptation of muscle fibers (p<0.0001), modulates the gene expression of FNDC5 (p<0.01), ITGB5 (p<0.01) and PPARGC1A (p<0.01), and induces an increase in peripheral protein expression of FNDC5 (p<0.005). Conclusion: Thus, we conclude that HIIT can prevent cognitive damage induced by the infusion of Aβ1-42, constituting a non-pharmacological tool that modulates important genetic and protein pathways.