Got 30 Minutes? Then You've Got a Workout.

Ever notice those people who show up at the gym, put in 15 minutes on the elliptical and...leave? It makes you wonder why they even bother. On the other hand, I've met a number of people who, if they can't carve out at least an hour in their day for a workout, won't bother.

The truth is, if you've got even a half hour to dedicate to a workout, you should use it. But you should make it worth your while. The most efficient workout you can squeeze into 30 minutes isn't complicated, though it is challenging. Here's what you do:

• Plan on doing mainly strength moves, but do them circuit style: perform one set of each exercise back-to-back with no rest, and then repeat the circuit twice for a total of three sets.
• Choose eight exercises (helps to plan these in advance) that work a variety of muscle groups, focusing on the body parts you want to work most: planks for your abs or reverse lunges for your butt, for example.
• Choose two additional exercises to insert into your circuit (I like to do one of these midway through the circuit and one at the end) that will serve as your "cardio" intervals, things like jumping jacks, squat jumps, or burpees, that will get and keep your heart rate up.
• Expect to spend 45-90 seconds on each strength move, and 30-60 seconds on each cardio interval. Each complete circuit should take roughly 10 minutes.
• Ideally, focus on bodyweight exercises, which you can do without having to set up equipment or move to another location, and use dumbbells, Body Bars, or medicine balls.
• Extra credit: Choose combo moves like lunges with bicep curls to get even more out of your workout session.

The best thing about a workout like this is that you can take it anywhere. No gym required=no more excuses.