Bioenergetics of the combat sports brain: Between risk and resilience.

Combat sports provide a unique human model in which cerebral ischaemia-reperfusion stress, adaptive neuroprotection, and impact-induced neurodegenerative risk coexist. Across striking and grappling disciplines, exercise-induced metabolic and redox stress, repetitive head impacts and transient cerebral ischaemia-reperfusion during vascular neck restraints expose the brain to competing adaptive and injurious stimuli. Cerebral ischaemic preconditioning (cIPC) research demonstrates that brief, sublethal reductions in cerebral blood flow (CBF) activate a conserved hormetic programme involving modulation of oxidative-inflammatory-nitrosative stress (OXINOS), reduced glutamate excitotoxicity, mitochondrial stabilisation, anti-apoptotic and autophagic pathways, and metabolic reprogramming. These responses preserve glucose-and lactate-dependent bioenergetics, neurovascular unit integrity, and cognitive function. Repetitive sportive strangulations may engage cIPC-like mechanisms, potentially explaining elevated basal CBF reported in elite Brazilian jiu-jitsu athletes (~500 pre-syncopal exposures per year). In contrast, repetitive impacts and rotational shear in boxing and mixed martial arts initiate neurometabolic cascades marked by axonal injury, exaggerated OXINOS, mitochondrial dysfunction, and neurovascular disruption, promoting tau pathology associated with chronic traumatic encephalopathy. By integrating cerebral bioenergetics, hormesis, ischaemic tolerance and traumatic brain injury, this review positions combat sports as a translational model for defining cerebral resilience and the balance between adaptive neuroprotection and cumulative neurological risk.