I started doing this a week ago after about 5 years of a desk job I don't even stand up very much most days. I'm not too fat because I eat well but even the 5 minute casual workouts are kicking my butt. How long will it take for this to get easier...I'm not trying to get super buff or anything. I just want to get my body working so I don't die early.
Yeah if you pay attention to just a couple points of the workout, like the one exercise you find you crap out on, you'll notice you're during more reps within a week or two.
I in no way consider myself very "gung ho" about working out. I don't go very hard I don't go very long, but I do push my comfort zone a bit every time. Sure sometimes a workout kicks my ass completely but mostly I start taking little breaks before I get to that point. I have yet to do a workout on here where I fill up each allotted exercise time with full time effort. But I've made a lot of progress since I began and I'm quite pleased.
You don't have to push to that point of near-death, especially if you're more likely to hate it and eventually stop exercising. Just do what you're comfortable with, and then a little more than that, each time, and you'll make steady progress without torturing yourself (and without making yourself more likely to quit) Don't be too frustrated by the level you're at right now, just keep an eye on the little progress you make. It won't be very long before you're doing a couple 15-20 minute "intense" workouts a day and feeling damn good about it. Good luck.