So i am really big into cardio, i love it, i do it 6 times per week every morning before breakfast, even on work days. It makes me feel good and healthy and it helps on a cut as well. Today I was working out at my local gym and walked into the nutrition center where I know the owner to be a very big and dedicated bodybuilder. I have known him for several years (but i never buy anything from him because its crazy expensive and a rip off)....So my question to him was if by doing cardio every day (45 minutes elyptical) if i was going to mess up my metabolism and slow it down because it would get used to it...His answer was no, but then he also stated that doing the elyptical is a big waste of time and that it does not do anything...so he said that the best thing to do is either run, or walk on the treadmill..well, im a big boy (220 pounds, 13%BF) and running hurts my knees and dedication, so im not running..........But it surprised me when he said that walking the treadmill is better than the elypitical........He brings up good points, only people doing the elyptical are fat out of shape people, you never leave the ground and just keep goind in circles.....But he said that when you walk, you are actually moving and doing something which burns more calories...if that is correct then why after doing the elyptical for 45 minutes do I feel tired, and I sweat so much that it looks like i took a shower in my shirt??? IM confused, would the more advanced people here explain ?