Demi Lovato just knocked out Sylvester Stallone ... and not just with her looks!

The badass babe is known for her incredible fitness routine, and she's partial to boxing.  We're loving this video of Demi and the original Rocky Balboa facing off at the boxing gym!  Better watch out, Sylvester!

Sylvester followed up with a cute caption saying he was boxing with his "long lost daughter, Roxana," at former fighter Jay Glazer's elite gym (you might recognize Jay from NFL or Fox Sports!).  The gym?  Unbreakable Performance Center — a favorite of Dwayne "The Rock" Johnson.

A nutritious diet and regular exercise have helped you reach your weight-loss goal, but you're still trying to get rid of that little extra pooch around your mid-section.  Here are three things you can do every week to help you achieve a trimmer belly.

When Eating

Take an honest look at your diet and your bathroom schedule.  Your belly might not be caused by fat, but by air trapped in your digestive system.  If you're not getting enough fibre (you need 25 to 30 grams a day), constipation can cause bloating.  On the other hand, overdoing it on fibre or eating too many gas-producing foods like broccoli, apples, or beans can also make your belly pooch a bit.  Thankfully, there are also foods you can eat, like blueberries, that are proven to diminish belly fat, so sip on this flat-belly smoothie made with pineapple and kale.

When Doing Cardio

Studies show that including interval training in your cardio sessions is proven to diminish belly fat.  If you find that you normally stick to a consistent pace when running, biking, or swimming, mix it up by adding 10- to 60-second fast-paced or sprinting intervals.  High Intensity Interval Training (aka HIIT) works on the same principle as intervals, where you push to your maximum training for a period of time and follow up with a shorter rest period.  Give this type of workout a try with our full-body 10-Minute HIIT Workout.

When Strength Training

Basic crunches can help tone your abs, but they only target certain abdominal muscles.  Incorporate full-body exercises like variations of plank or core moves using a ball.  Simply balancing on one leg on a Bosu will target your core too.

You've been eating right and exercising for a while, but that stubborn belly fat just won't budge!  Along with incorporating foods that fight fat into your diet, here are some ways to burn that pooch away while you are out on a run.

Switch Up Your Pace

Intervals are proven to reduce belly fat and rev up metabolism;  instead of running at the same pace for the entire workout, try alternating between periods of pushing your body to the max and periods of recovery.  Here's a list of interval workouts for you to try:

• 45-minute fat-burning treadmill workout
• 300-calorie-burning walking-jogging workout
• 30-minute pyramid intervals
• Swimming interval workout
• 45-minute walk-run-sprint workout
• 45-minute elliptical interval workout

Go a Little Longer

Unfortunately you can't spot treat when it comes to weight loss, which is one reason solely doing crunches won't whittle your waistline.  The key is to decrease overall body fat, and the one way to do that is to burn calories.  Lengthening your workout will do just that.  Every five minutes of running at a 10-minute-per-1.5km pace burns about 45 calories.  Think about that on your next run, and it'll motivate you to keep going!

High Knees

You're working hard to diminish your overall body weight, which will slim down your belly, so you can reveal toned abs underneath.  Here's one way to strengthen your core.  Do one-minute intervals in which you run with high knees (like in this cardio workout you can do in your living room).  Concentrate on using your abs rather than your leg muscles to kick your knees up as high as you can.

Try This Killer Treadmill Move

Here's another core killer if you're using a treadmill.  Set the pace to 1.0 mph.  Place your feet on a Plyo Box that's set up about two feet behind the back of the treadmill.  Come into plank position with your hands straddling the treadmill belt.  Step your hands on the belt and start walking, keeping your torso in one straight line.  Do this for one minute, pulling your belly in toward your spine.  Watch the above shredmill move in action here!

Not every workout has to be a no-holds-barred sweat fest, but we're not going to lie:  those days when you crush it at the gym are the ones that are going to help you see results fast.  So pound that pre-workout shake, and take this hour-long workout with you the next time you want an effective workout.  The intense workout is one of Michelle Bridges's secrets for burning calories fast, and it's not for beginners.  This particular workout from Michelle's newest book, Total Body Transformation, comes at weeks nine and 10 of her 12-week plan, so if you're new to the gym, then start off slow, modify, or try one of our beginner-friendly workouts instead.  If you're up for a challenge, however, check out the workout below, learn the moves, print this chart, and get ready to burn calories and boost your metabolism.  To start, do a warm-up:  three minutes on the rowing machine, ending with a 500-metre sprint.  Follow it up with 20 minutes on the treadmill (Michelle recommends 8 to 9 kph at 2 percent incline for 20 minutes or 10 minutes at 8 to 9 kph and 2 percent incline followed by 10 minutes at 5.6 kph at 12 percent incline.)  Aim to get your heart rate up to 150 bpm by the end of your warm-up.  Then follow with these two circuits below, repeating each circuit three times.  End with a cooldown stretch.  This workout is made for the gym, but you can modify any of these moves to suit the equipment you have at home (jog in place or use dumbbells in place of the barbell, for example).

Walking Push-Ups

If you don't have a bench, you can perform this move on the floor or with one hand alternating on a medicine ball.  Lower to your knees if staying on your toes is too difficult.

• Place one hand on the end of a low bench and the other hand on the floor.  Your hands should be slightly wider than shoulder-width apart.  Lengthen your torso, draw your abs in, expand your chest, and drop your shoulders down away from your ears.  Keep your neck long and your chin tucked in, and look at the floor directly ahead.
• Bend your arms, and inhale as you lower your upper body to about four inches off the floor.
• Exhale as you straighten your arms to return to the start position, and then hold your body strong as you swap hands to the other side and alternate the push-up.  This counts as one rep.
• Do 20 reps.

Forward and Backward Jumps

• With your feet hip-width apart, point your toes and knees straight ahead, keep you knees soft like shock absorbers, pull your abs in, and elevate your chest.  Jump over a line (or a rope or a towel) and back again.  Land softly!
• Do 20 reps.

Standing Shoulder Press

Start with nine kilos for this workout and modify if necessary; your arms and shoulders should feel fatigued by the last rep.

• Holding a barbell (or dumbbells), stand tall with your feet in a staggered stance.  Your front knee should be soft and take most of your body weight;  the ball of your back foot should be on the floor, your back leg acting as a prop to stop you from leaning backward.  You should feel rock solid.
• Keeping your midsection braced, exhale as you drive the barbell toward the ceiling, keeping it slightly forward of your face at the top of the movement.  Do not lock your elbows;  keep them slightly bent.  And do not push the bar back behind your head.
• Inhale as you carefully lower the barbell to the start position.  Look forward throughout the movement, and take care not to arch your back.
• Do 20 reps.

Ice Skaters

• Lay a towel down or set up a low platform, and take a long, low leap over it sideways.  Swing your arms strongly in the direction you are travelling, and land the foot solidly with the toes and knee aligned (slightly angled out).
• Bend into the leg before you push off, leading with the other leg and repeating for the opposite side.
• Do 20 reps.

Backward Power Lunge

• Stand tall, hands on hips, looking straight ahead.
• Inhale, and take a long step backward, keeping your feet hip-width apart and your weight evenly distributed between your front and back legs.  Both legs should be bent at an angle of 90 degrees.
• Exhale, and powerfully push off your back foot to get you back to start position.  Repeat for the opposite leg, and then alternate legs, or do several reps on one side before you swap.
• Do 20 reps for each leg.

Sideways Running

This move will help increase your agility.

• Starting with your right foot, run five steps sideways to the right.  On the last step, your right foot should "stick" as you first drop your weight into that leg before pushing off with it and stepping out with your left.  (When you plant your foot on the last step, your whole foot should be in contact with the ground and slightly angled out in the direction you were heading.  Make sure your knee is pointing in the same direction as your toes.  Keep your shoulders back and down with your chest up and abs in, and swing your arms to give you momentum.)  The timing should feel like "one, two, drop and push, one two, drop and push."
• Repeat by running to the left side for five steps.
• Do 20 reps.

Finish the circuit with five minutes of indoor cycling before repeating the entire circuit for a total of three times.

Ab Work

Now it's time to work those all-important abs.  Repeat this section three times.  Start with a nine kilo ball for this workout, and modify if necessary.

Supported Crunch With Medicine Ball

• Sit on the floor, and tuck your feet under a support such as a weighted bar, a ledge, or even the edge of your couch.  Bend your knees to 90 degrees, and roll back, lying flat and holding the medicine ball directly above your chest.
• Exhale as you lift your body upward toward the ceiling.
• Drawing the abs in tight, inhale, and lower yourself down to the start position.
• Do 20 reps.

Supported Crunch With Medicine Ball With Twist

• Repeat as above, except as you lift your upper body, bend your right shoulder toward your left leg.  This is one rep.
• Repeat, this time twisting so your left shoulder reaches toward your right leg.
• Do 20 reps.

Supported Crunch With No Ball

Finish with 20 reps of supported crunches, this time with no ball in your hand.

Print this chart.

Accomplishing certain yoga poses can feel like completing a magical spell or winning a game of Quidditch.  One Austin-based yoga teacher combined those two feelings into one spellbinding Harry Potter-themed class.

The onetime class was held at Circle Brewing Co., a local brewery that frequently hosts yoga classes and other events.  In this installment, yoga teacher Isabel Beltran put together a creative class that incorporated wands into certain poses and encouraged attendees to wear their finest Harry Potter fitness gear.  (Yes, that's a thing.)

At the end of the class, Isabel read a passage from a book in the series as attendees closed their eyes in Savasana.  Afterwards, everyone was treated to thematic treats and beer from the brewery.

Look ahead for pictures from the dreamy class.