Find a sturdy bench, coffee table, wooden box, or kid's chair that, when you place your foot squarely on it, your knee is at about a 90-degree angle or larger.
Hold a dumbbell in each hand by your side.
Step up onto the chair and lift your right knee forward and up.
Lower the right foot back to the ground, landing softly.
This counts as one rep.
Step up onto the chair and lift your right knee forward and up.
Do as many reps as you can for 40 seconds, alternating which leg you step up with each time. Rest for 20 seconds.