you've responded to a very old post. lol.
Anyway just to follw up you are exactly right. Why would you want the pump when you run. When i am done lifitng and i have that pump the last thing i am thinking about is running fast or even being able to run at all. I guess it could be a good supplement if you want to look good on the beach and possibly a good cosmetic supplement for bodybuilders.
The supplements claim to fame is that since it is giving you that pump which is actually your blood flowing it should aid in recovery since the blood is moving nutrients around your body to repair tissue. That is why arginine 5-10 grams by itself could help aid in recovery.