Sitting on the ground, loop your resistance band around the top of your feet. Lay on your back and lift your knees to line up above your hips, bent at 90 degrees. Keep your feet flexed towards your shins and slightly apart to hold the band in place. Clasp your hands in front of your chest comfortably, and bring your lower back down to rest on the floor: stay grounded here throughout this movement. Knees elevated, drive one foot into the band until your leg is fully extended in front of you. Bring your knees back together, and repeat on the opposite side. Keep your abdomen engaged and ribcage firm against the floor to protect your back. With each extension, release a sharp pressurized breath, inhaling as you return your leg to its starting position.