WORCESTER When it’s in motion, Gwynedd Mercy Academy’s defense is a problem. A problem for the opposition, to be accurate, with a carousel of long arms, traps, pressures and rotations filling passing lanes, deterring drivers and disrupting sets. GMA is built on defense and when it’s in motion, there’s a reason the team’s players like being a part of it. The Monarchs had their defense in motion Saturday, giving a young Methacton team a too-real lesson in a 58-18 win.