You can take a break in between each cycle, but you may find that you just want to power through since you can't put down the weight.

2. The Ballerina Workout

Don't let the small movements and light weights fool you. The high reps in this ballet-inspired workout will make you feel the burn while you sculpt lean muscle and improve your balance at the same time.

Grab a pair of light weights (3-5 lbs) and stand next to a chair or barre. Repeat the following sequence twice.

3. Prison Workout

Why the name? Prisoners only have a small cell to work with, and while you may never be in the exact same setting (hopefully), sometimes you need a workout that hits every muscle group without needing a lot of space or equipment. Pushups and squats may not be the most exciting moves, but there's a reason they're staples in almost every workout: They work!

Complete this circuit as many times as you can in 15 minutes to burn fat and build lean muscle fast!

4. Leg Burnout

Rachel Cosgrove, author of The Female Body Breakthrough, says this workout is part of her build-a-butt plan because of the awesome shape and definition it gives your backside. Alternating squats and lunges and grounded and plyometric moves keeps all of your leg muscles engaged while offering enough variety to take your mind off the burning sensation!

Complete the full sequence twice, resting just enough between sets to catch your breath.

5. Pyramid Workout

The simple design of this workout can be deceptive (It's hard!). By combining these two power moves, you'll be able rest one muscle group while fatiguing the other without taking a break.

Start by doing 1 rep of each exercise. On the second set, do 2 reps of each exercise. Continue this pattern until you've done 10 sets, and then come back down the pyramid until you're back to 1 rep.

6. Plyometrics Power Plan

Plyometrics refer to any move where both of your feet leave the ground at the same time. While these intense exercises aren't for everyone (skip them if you have knee, hip, back, or other injuries), they amp up the intensity of your workout like nothing else can.

You'll be soaked in sweat long before your 15 minutes are up!

Do each exercise for 1 minute, moving from one to the next without rest in between.

After you finish the last move, rest for 1 minute and repeat the circuit 2 more times, 3 times total.

7. Jump Rope Intervals

Nothing beats jumping rope for ease and accessibility. Plus, research shows that intense interval training like this workout burns more fat than steady-state cardio and increases your metabolism for up to 48 hours after your workout is over. When you add the strength moves, using your own body weight for resistance, you've got a killer total-body routine—not bad for a 15-minute investment!

8. Kettlebell Kickboxing

Why settle for one or the other when you can have the fat-burning benefits of kickboxing and the strength work of kettlebells? This killer combination allows you to incorporate on the hottest fitness tools into a traditional, heart-pumping workout.

Grab medium weight kettlebell and try this high-energy mashup designed by Dasha Libin from Kettlebell Kickboxing in New York City. Perform each exercise for 1 minute and then immediately move to the next. Rest for 1 minute between each circuit.

Circuit 1:

Circuit 2:

Circuit 3:

9. Resistance Band Frugal Workout

This quick workout incorporates a resistance band, one of the least expensive pieces of fitness equipment available, to help intensify strength moves beyond what you'd get using just your body.

Michael Schiemer of Frugal Fitness recommends going through this circuit three times.

You'll need a resistance band, a Swiss ball, and a 10-15 lb dumbbell.

10. 12-Minute Madness

Called "the home workout revolution," Bodyrock.TV made its mark on the fitness world by providing short and intense workouts, but they earned their legion of devoted fans by coming up with creative moves like "the drunk chicken."

There's a reason this plan is called 12-minute madness! Perform each of the following moves for 50 seconds, resting 10 seconds between each. Work through the entire circuit once.

11. Kettlebell Workout

Kettlebells have become the workout du jour for a good reason: The swings amp up your heart rate while the power moves engage every muscle in your body, resulting in a workout that's as effective as it is fast.

Choose a kettlebell you are comfortable swinging and try this circuit, created by Jenn Nims of Girl-Heroes. 2-3 times. Do each move for 40 seconds, resting for 20 seconds between moves. Complete the entire circuit 2-3 times. (You can see a video demonstration of the moves here.)

12. Cardio Kickboxing

You'll notice the cardio burn first during this short-but-intense kickboxing circuit, but thanks to the punching and kicking drills, you'll feel the burn in your upper back, lats, quads, and even calves the next day.

Use a heavy bag if you have one available. If not, ask a friend to hold focus mitts/pads for you or simply punch and kick the air. Do each exercise for 50 seconds as hard as you can, rest 10 seconds, then move on to the next exercise. Go through the entire circuit once.

13. Exercise Ball Challenge

Incorporating an exercise ball into your normal routine not only challenges your core strength and balance, but it forces you to focus on performing the moves in a controlled way.

Grab a large Swiss ball and a set of dumbbells. Choose a weight that is heavy enough so that you can complete no more than the prescribed number of reps with perfect form. Repeat the full circuit below 3 times.

14. 15-Minute Yoga Flow

You don't have to know where your chakras are (or even what one is) to get the physical and mental benefits of a vinyasa—"a steady, dynamic flow of connected yoga asanas linked with breath work in a continuous movement." The continuity and focus on breathing helps release serotonin (the feel-good hormone in your brain) to calm your mind, while the movements challenge your balance and strength.Go through this vinyasa flow once, moving through the steps as fluidly as possible.

15. Quick Cardio Blast

Sprint training is powerful medicine. Studies conducted by Izumi Tabata found that short, intense sprints (by "intense" we mean "run as if the zombie apocalypse is upon you") offer benefits like increased aerobic capacity, fat burning, and production of human growth hormone—the closest thing to the fountain of youth that scientists have been able to find. Try this killer cardio blast:

Repeat the circuit 3 more times (4 times total), cutting the walk time in half every time.