A 12-week high-intensity interval training program significantly improved hippocampal structure and connectivity in adults with moderate to severe cannabis use disorder, while strength training showed no similar benefits. The randomized trial of 60 participants demonstrated that HIIT's lactate-generating mechanism specifically enhanced brain regions critical for memory and executive function that are typically compromised in chronic cannabis users. This represents the first controlled evidence that targeted exercise interventions can reverse neurological damage associated with substance use disorders. The implications extend beyond cannabis dependency, as hippocampal deterioration underlies cognitive decline in aging, depression, and neurodegenerative diseases. The lactate hypothesis—that high-intensity exercise creates metabolic conditions promoting neuroplasticity—gains credibility from this work. However, the study's modest size and 12-week duration leave questions about durability and broader applicability. The finding that participants weren't required to cease cannabis consumption makes the neurological improvements particularly striking, suggesting exercise interventions could complement rather than replace traditional addiction treatments. For health-conscious adults, this reinforces HIIT's unique neurological benefits compared to moderate-intensity exercise, especially for cognitive resilience.