With a seemingly never-ending to-do list and a daily time crunch, squeezing in a workout can seem like an impossible feat. Many people simply give up on the idea of working out regularly when their schedule's full, but the latest fitness craze involves adding a quick workout to your lunch hour or midday routine.

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Fitness centers like Curves and other "fast-fitness" destinations promise to give you a total body workout in less than an hour. Thirty-minute circuit training and fast-track fitness routines are making it easier for people to maintain a fitness schedule and exercise program. But do these express workouts really work?

If you're the type of person that wants to maintain a steady workout schedule and commit to an exercise plan, an express workout may be a good fit for you. However, if you're interested in losing weight and really transforming your body, you won't get many results from a quick 30-minute routine.

In order to make a significant difference and lose weight or increase muscle mass, you'll need to maintain a steady schedule of cardio and weight training throughout the week for at least 45 to 75 minute sessions each.