Resistance training reversed functional brain aging by 1.4 to 2.3 years in healthy adults, based on brain clock models trained on 2,433 participants. The LISA randomized trial tracked 309 adults across two years, finding that both moderate and heavy resistance training significantly reduced predicted brain age compared to controls, with heavy training producing the largest effect. The benefits emerged at the whole-brain network level rather than isolated regions, while heavy training specifically increased prefrontal connectivity. This represents compelling evidence that strength training delivers measurable anti-aging effects on brain function, not just structure. The brain clock methodology—using resting-state fMRI to predict biological age—offers a sophisticated approach to quantifying neurological benefits of exercise interventions. While promising, the study's two-year duration captures relatively short-term changes, and participants were already healthy adults rather than those with cognitive decline. The hierarchical brain aging model proposed here could reshape how we understand exercise neuroprotection, suggesting distributed network improvements drive regional benefits rather than the reverse.