The post references a real 2015 King's College London study on older female twins. Greater leg power at baseline predicted better cognitive outcomes and more grey matter volume ~10 years later—even within identical twin pairs (controlling for genetics/early environment).
Leg muscle contractions release myokines (signaling molecules) that support brain health, alongside better blood flow from movement. Resistance work like squats helps.
That said, "larger brain" and "cheat code" is hype. It's a strong association and useful marker of fitness, not proven direct causation or magic. Correlation, with leg power likely proxying overall activity levels.
Train legs regularly—great habit. Pair it with sleep, nutrition, and lifelong learning for real brain protection. Solid nudge to move, though.