When i do a hard track workout, or a race over a mile it seems like my forearms and shoulders are severely filled with lactic acid, moreso than my legs, probably about 1.5 miles in a 2mile or about 2 miles into a 5k, I'm not going out too fast since i usually negative split. In fact my arms are the first thing to go in a hard race. It is really uncomfortable, and hard to go fast when you can't pump your arms. Anyone else have this problem, and know why or how to fix it?
Most likely your shoulders are crunched. Try to relax them and keep your hands next to your waist. Watch Nick Willis run. Try that.