I will pre-empt this question with pointing out the possibility that it may be that I've slept funny on my arm, but I'm not entirely certain, since it's not the first time!
Basically, I went for a run this morning, and all day today, my left arm/shoulder/elbow has been aching horrendously. It feels a bit like I've had an injection or blood test, and is suffering a bit, but is more uncomfortable than anything. I feel the need to constantly keep it moving, as if I'm lacking blood in my arm!
Any ideas on what might be causing this? I saw something on RW that mentioned that it might be through clenching my fist when getting tired in running - it seemed logical, but wasn't sure that it should be hurting for the rest of the day!