▼ The expression in Hebrew uses מְזִיחַ (m^eziakh, “belt”) and the Piel verb רִפָּה (rippah, “to loosen”) so that “to loosen the belt of the mighty” would indicate “to disarm/incapacitate the mighty.” Others have opted to change the text: P. Joüon emends to read “forehead” – “he humbles the brow of the mighty.”

▼ The word אָפַק (’afaq, “to be strong”) is well-attested, and the form אָפִיק (’afiq) is a normal adjective formation. So a translation like “mighty” (KJV, NIV) or “powerful” is acceptable, and further emendations are unnecessary.