When it comes to cardio, Lori is a believer but she knows it's not enough to work out. You need to work smart, like Libby DiBiase.

Libby says, "Cardio really blasts the fat off. You can't really have a good body without starting with cardio."

She does that by exercising at a moderate intensity. Think of it as a seven to eight on a 10-point scale. The monitors on cardio equipment can be a guide but they're not gospel.

Lori says "The info it's not asking you -- what your body fat is, how much lean muscle mass you have, and it's not going to ask you if you're on any medicine that could alter heart rate."

Seasoned exercisers like DiBiase can easily find their target heart rate. If that's confusing, Johnson says try the "talk test."

"If you're breathing hard and can communicate with somebody, you're working at a moderate level," she says.

Keep in mind that each piece of cardio equipment works our bodies a bit differently. When we cross train on the stair mill or something else, we'll see a difference.

Lori says "If you do the same old same old, you're going to look the same old same old. So if you're looking to make a change in your body, in the way you look, you need to change it up."

It's worked for Libby. She does cardio six days a week and not only looks great but feels great.

You should aim for 30 minutes of moderate intensity exercise, five days a week. But here's the good news: you can break it up into something like 10 minutes on the treadmill in the morning, the stairs at lunch, and a walk around your neighborhood after dinner.