I've been having some issues doing dips lately that I wanted to throw out there to see if anyone had any ideas. I appreciated your input with my squat question (an issue which hasn't reappeared, strangely enough), so here's this. I do weighted dips with about a 4 second negative, normal concentric, to failure; then I rest 15 seconds, and I repeat this two more times. The last few times I have done dips this way my abs feel supremely sore, and I start getting very nauseous. But the last 2 times I did this, I've also begun getting a pretty intense neck pain that leads to a headache. Am I doing something wrong here?