User blog comment:Kogath/Monster Hunter Generations Discussion/@comment-28908045-20160813221851/@comment-5167887-20160813224549

Been wondering this as well before i got what was happening.

That's actually the effects of the Ace (Chance) armor skill. After a monster has been disabled (trap, KO, mount, etc...) a faint yellow glow will appear on your character's arm. While this is active, Hunter Arts are 30% more powerful: this increases the damage they cause, and for non-offensive ones, they gain various bonus effects (longer duration, etc...), including a double dodge with Absolute Evasion.