Using a bench or step of some sort, start with one foot up on the bench. Step up and switch to the other foot on the bench and keep alternating to create a sprinting/stepping motion to get your heart rate up.
Grab a med ball or a low step and run in place driving your knees up, alternating tapping each foot on top of the ball or step. Keep your core tight throughout the exercise.
Beginning (gram on the left) - Using a pillow on the ground, alternate stepping with one foot and tapping other the foot on the pillow. Keep switching and alternating. Intermediate (mom in the middle) - Using a pillow on the ground, alternate hopping and tapping feet....
Alternate lifting your knees up and down as high as you can get them, as fast or slow as you want to go to get your heart rate up.
Start on the ground on your hands and toes in a push-up position. Jump feet out and bend arms to a push-up, then press back up and jump feet back together.
Starting in a standing position, bend down and touch your hands to the ground. Jump both feet back to push-up position, then jump both feet back in and jump to come up. Repeat this sequence for every rep.
Find two paper plates or two things that slide on the carpet. Get in a push-up position with your hands and toes on the ground and one foot on each plate. Alternate driving knees into your chest/sliding plates in and out alternating.
Standing on the ground, place one arm on the ground and jump both feet back and out to a push-up position with your other arm up above your head for balance, then jump both feet in and jump back to starting position.
Start on the ground on your elbows and toes in a plank position. Roll onto one elbow while reaching the other arm to the ceiling, keeping your core and side tight. Then roll back to plank and repeat on the other side. Continue alternating sides for each rep.