I just started working out. I have to pass a Physical Fitness Test for a new job. I've lead a sedentary lifestyle for most of my life. I am 33, 5"2, 140lbs - Female. My 1st day of working out I was able to do 27 situps in a minute. My 2nd day, I was only able to do 12.. What gives? I am still sore but shouldn't I be doing more than the 1st day or at least the same?!