Lymph Nodes Swell During Exercise?

I used my weak google-fu and found nothing.

My friend, when bicep curling large weights (<3 reps), has little bumps on his forearms that are only there during the exercise. I don't know why, and I'm not sure if they are lymph nodes, but I'm going to say that they are since they're the only large circular structures I can think of. I'm just curious about this - It doesn't hurt him, but I don't think there is a reason things should swell like that during exercise. Veins popping up, I understand. These are definitely not veins.

Anyone got an explanation? Should he avoid this sort of thing?

No, that's not it. Probably just blood vessels.

Let's say they are blood vessels... Would this mean his blood pressure is going nuts in only one part of his body? Doesn't make sense to me.