Bulk Up (5e Feat)
From D&D Wiki
Prerequisites: Must be a muscle wizard, have at least 23 strength, and can only get at level 18 ability score improvement.
With days and nights training your body you have achieved per physical fitness with a cost, that cost being movement. Your Strength score increases by 7. Your max score for Strength is now 30. Your maximum speed is reduced by 10 feet.