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.

How to Add Cardio to Your Circuit-Training Sessions Without Doing Cardio

Let's say you've already implemented the oft-recommended strategy of doing your strength-training routine circuit-style. That is, you do all or a group of your resistance exercises back to back with no rest in between moves. (An example would be single-arm rows followed by Romanian deadlifts followed by biceps curls followed by dumbbell side crunches.) You're getting your heart rate up, breaking a sweat, getting in and out of the gym quicker than ever.

But you don't have a complete workout---not just yet. Chances are you still need to supplement your strength exercises with at least 20 minutes of cardio (right?), which can get time-consuming. The good news: you don't have to work out this way every time.

You can sneak brief bouts (30-60 seconds) of cardio into your strength routine at regular intervals to maintain an elevated heart rate for the duration of your circuit workout. This is considered high-intensity training. Let me give an example. Let's say you have ten exercises you want to complete (abs included). Divide these into two circuits of five exercises each, including a variety of muscle groups in both circuits so that you can perform the exercises back to back. Circuit 1 might include dumbbell chest flies, crunches on the bench, squats, push-ups, and a plank hold. Complete one set of each, and then immediately following your plank hold do 60 seconds of jumping rope or squat jumps. Rest for a minute or two, then repeat the circuit for a second (and, if you wish, third) set.

Here are some options for cardio intervals you might include in your workout:

• Jumping rope
• Jumping Jacks
• Squat jumps (squat down, jump up, land softly in a squat, repeat)
• Lunge jumps (drop into a lunge, jump up, switch legs and land softly in a lunge with the other foot forward, repeat)
• Cross-country skiers (like lunge jumps but don't lower body weight toward the floor)
• Bench step-ups
• High knees
• Butt kicks
• Speed skaters (take a big jump out to one side with your right foot while crossing your left leg behind you and touching the floor or a cone with your right hand; jump back to left and repeat)
• Up and overs (stand to one side of a bench or aerobic step; plant one foot firmly on top of the bench and step or jump sideways over the top, landing on the other side with your opposite foot planted on top; repeat)
• Mountain climbers
• Side-to-side shuffles

This list can go on and on. Anything that keeps you moving consistently and continuously for a period of at least 30 seconds and gets your heart rate up counts as cardio.

Note: You should still be a little winded while doing your weight exercises, and your heart rate should feel elevated. On a difficulty scale of 0 to 10, if zero is resting and 10 is sprinting for your your life, your cardio intervals should feel like at least an 8 and your lifting intervals a 6. If this is not the case, you may need to do one cardio interval every three strength exercises instead of every five.

Adding regular cardio intervals will increase the intensity of your circuit-training session and combine elements of cardio and strength for a complete workout. If you always do separate strength and cardio sessions, try substituting this workout twice a week for renewed results.