Lately when I go heavy on SLDL's I have some discomfort in my lower abs, like right along the belt line, only on one side though. When I'm doing them I can feel kind of a straining sensation in the area, then for a couple days after it's tender to touch or tighten the abs. I thought about wearing a belt when I go heavy, but I really don't want a crutch. Anybody have any idea why this is happening??