I have all of Cathe's tapes and I absolutely LOVE them. My problem is that I can rarely do more than 35 minutes of cardio without pooping out, despite using low impact modifications. I have been excercising for years and have used Cathe's tapes for about 4 years. I have a stressful/ tiring job (elementary school teacher) and I have low blood sugar which leaves me feeling pretty low energy most days. I get enough sleep and drink enough water. I worry that I won't be able to burn enough calories. I do cardio about 4-6 times a week and one muscle group a day usually 5 times a week. Do some people just have less energy than others? Thanks for any imput!