I've recently bought 1 Nike and 3 Under Armor shirts...I've been wearing them as a base and then a couple of t's over that...It seems I feel more able to push a little harder than usual...I have something to constrict against and it feels like it's giving me a rep or 2 more on the bench and shoulder presses...Anybody use those shirts...I have 3 short sleeves and 1 long sleeve...