I am one of the guys who sweat a lot. But I am fit. I go to gym almost every free evening and run on the treadmill for about 1.6km for 8-9min after I do weight training such as push up, pull down, situps and lift some weights. I will look like bathed after 10min of running. You can imagine, the sweat is full of my T-shirt and even drips down. However, I realize that when I play tennis, I lose my stamina very fast. I get tired after a set, then I will double-fault a lot. I mean, I have slimmed down after all these training, lost 6kg, and pumped my stamina up, but the benefit doesn't propagate to the tennis games. So I wonder whether it is due to my sweating. Is extreme sweating making me lose my stamina so fast? Anyone has similar problems and any idea what's wrong?