We're big fans of Aussie trainer and founder of the Sweat With Kayla app Kayla Itsines, and we're delighted to share this killer leg workout she created for us.  See the exercises in the video, then read below for additional instruction and tips from Kayla.

Instructions For Leg-Toning Circuit Workout

Start a timer for seven minutes and aim to complete the exercises in the below circuit as many times as you can before your timer goes off.  While you're aiming to complete each exercise as quickly as possible, it is important that you maintain proper technique throughout.

In and Out Jump Squat

Plant both feet on the floor further than shoulder-width apart.  Point both feet slightly outward.  Looking straight ahead, bend at both the hips and knees, ensuring that your knees point toward your toes.  Continue bending your knees until your upper legs are parallel with the floor, ensuring that your back remains between 45 and 90 degrees of your hips.  This is called sumo squat position.  Propel your body upward into the air.  Reposition your legs to land in close squat position, with your feet a fist-width apart.  Continue bending your knees until your upper legs are parallel with the floor, ensuring that your back remains between 45 and 90 degrees of your hips.  Propel your body upward into the air and reposition your legs to land in sumo squat position.  Continue alternating between sumo squat position and close squat position for the specified number of repetitions.

Tip:  Ensure that your knees remain in line with your toes for both of these movements.

Alternating Front Lunge

With your hands on your hips, plant both feet on the floor slightly further than shoulder-width apart.  This is your starting position.  Take a big step forward with your right foot.  As you plant your foot on the floor, bend both knees at approximately 90 degrees.  This is called a lunge position.  Transfer your weight onto your left foot and take a large step back with your right foot to return to starting position.  Repeat, stepping forward with your left foot.  Continue alternating between right and left lunges for the specified number of repetitions.

Tip:  Ensure that your front knee is not more forward than your toe and that your weight is evenly distributed between both legs.

X Hop

Plant both feet on the floor slightly further than shoulder-width apart.  Looking straight ahead, bend at both the hips and knees, ensuring that your knees remain in line with your toes.  Continue bending your knees until your upper legs are parallel with the floor.  Ensure that your back remains between 45 and 90 degrees of your hips.  This is called squat position.  Propel your body upward into the air.  Extend and reposition both of your legs to land in a lunge position with your left leg forward and right leg back.  Ensure that your weight is distributed equally between both legs.  Immediately propel your body upward into the air again.  Extend and reposition both of your legs to land back into squat position.  Immediately propel your body upward into the air again.  Extend and reposition both of your legs to land in a lunge position with your right leg forward and left leg back.  Continue alternating between lunge and squat movements for the specified number of repetitions.  Each movement of the feet is equivalent to one repetition.  Breakdown:  The sequence will be:  squat, lunge left leg forward, squat, lunge right leg forward.

Tip:  Land with "soft" knees each time that you land to prevent injury.

We're big fans of Aussie trainer and founder of the Sweat With Kayla app Kayla Itsines, and we're delighted to share this abs workout she created for us.  See the exercises in the video, then read below for additional instruction and tips.

Directions For Abs Circuit Workout

Start a timer for seven minutes and aim to complete the exercises in the following circuit as many times as you can before your timer goes off.  While you're aiming to complete each exercise as quickly as possible, it's important that you maintain proper technique throughout.

Bent Leg Raise and Hip Lift

Start by lying flat on your back on a yoga mat and place both hands underneath your coccyx bone as shown.  Extend both legs out and engage your abdominal muscles by drawing in your belly button to your spine.  This is your starting position.  Keeping your feet together, contract your abdominal muscles and bend your legs to bring your knees to your chest.  Allow your lower back to lift off of the floor as shown to allow full contraction of your abdominals.  Briefly hold this position and then slowly extend your legs to return to starting position.  Complete 15 reps.

Tip:  Tuck your knees all the way in to your chest to fully contract your abs.

Outward Snap Jump

Place both hands on the floor slightly further than shoulder-width apart with both feet together behind you, resting on the balls of your feet; this is your starting position.  Quickly jump both feet outward so that they're wider than your hips, as shown.  Quickly jump both feet inward to bring them back together into the starting position.  Continue alternating between feet together for 20 reps.

Tip:  Keep your shoulders in line with your hands.  Engage your core to keep your hips stable.

Straight-Leg Sit-Up and Twist

Start by lying straight with your back on the floor, both arms extended above your head.  Place both hands behind your head.  Engage your abdominal muscles by drawing your belly button in toward your spine; this is your starting position.  Keeping your heels firmly planted on the floor, slowly lift your head, shoulder blades, and torso off the floor.  Ensure that it's your abdominals that initiate the movement and that you do not use your arms to swing your torso up.  As you sit up, extend your left arm and twist over the right side of your body as shown.  Slowly untwist and lower your torso back into starting position.  Repeat using your right arm and twisting over the left side of your body;  this counts as one rep.  Continue alternating between left and right for a total of 20 reps.

Tip:  Your abs should be initiating this movement.  Avoid using your arms to swing yourself up.

Burn some fat and sculpt some muscle with Jeanette Jenkins, aka The Hollywood Trainer.  With clients like P!nk and Alicia Keys she lives up to the moniker.  This 30-minute workout mixes cardio with strength training for the ultimate sweat session.  Grab a set of five-pound dumbbells, press play, and get ready to work.

Everyone has to start somewhere.  And when it comes to cardio, working out in the comfort of your own home is a great place to start.  We created this 15-minute workout for beginners, complete with low-impact modifications for anyone who doesn't want to jump.  You don't need any equipment for this workout, just a can-do attitude.  So press play and get ready for your heart rate to rise.

Looking to tone up after having a baby (or two)?  We tapped celebrity fitness trainer, Ramona Braganza, who helped both Jessica Alba and Zoe Saldana get back in shape after having kids, to create a workout for new mums.  Based on Ramona's Baby Bulge Be Gone diet and fitness plan, this 20-minute workout mixes cardio, strength training, and ab work.  No matter your fitness level, this workout will work for you.  Ramona provides excellent modifications for beginners, as well as ways to advance the moves — "you can always make an exercise harder".  Grab a set of three-pound dumbbells, and a chair if you're just getting back in the fitness game, and let's get at it.