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.

Working Out...Or Just Goofing Off?

I can't help but notice that some people spend more time at the gym putzing around than focusing on their workouts: watching TV, checking themselves out in the mirror, or texting. Based on my (clearly very scientific) observations, the average person spends at least 3 minutes taking a break for every 30 seconds they spend lifting.

Now, regardless of your workout goals, I don't know of any fitness experts who would recommend this work/rest ratio. Bottom line: it's unfocused, and it's inefficient. And it often leads to gym sessions that drag on longer than two hours.

If you're serious about improving some aspect of your fitness---whether it's losing weight or gaining muscle---then you want to avoid this kind of aimless workout. (And if you're not serious about making a change, ask yourself: why do you do it?)

One way to accomplish this is to consider how much rest you actually need. Generally, the heavier you're lifting, the longer rest intervals you need. Your repetition range is what determines the weights you choose, so if you're performing only 6-8 reps with heavy weights, you'll need about 120 seconds of rest (your set will take up to 45 seconds). If you're doing 10 reps, rest up to 90 seconds, 12 reps, up to 60 seconds, and so forth.

If like me you like your resistance training in the form of high-intensity circuits, you don't need a dedicated rest period (save for catching your breath). This is assuming you don't work the same muscle groups back to back---you might do a set of rows followed by lunges followed by planks, or you might alternate between push and pull exercises, like chest presses followed by rows.

The best advice I can give to ensure your workout is efficient and effective is to have a plan going in. You don't have to write it down---you can plan it in your head---but try to really think about how you want to use your (precious!) time. Not only will you look like you know what you're doing (who really wants to wander around picking exercises at random?), you'll gain the confidence that comes with walking into the gym with a purpose.