No, the pumps seem to only effect the weight training aspect. My 200 Meter workout (repeats) yesterday was the best ever. And if you know about the 200, if the pumps effected me, then it would hit me in the last 50 meters.
I had a Meet......let's just say my times are better...lol. If I said what I did, then I might expose myself.
PS. I've gained 13 lbs. I cut 10mg of Winny back and will cut another 10 off tomorrow. (It's just too obviois)