One foot stays down while the other leg reaches back. It trains the glutes and hamstrings and shows you which side has been getting a free ride.

Diagrams show the shape of the movement. Follow the written steps before you add load.
Equipment. Dumbbell
Muscles. hamstrings, gluteus maximus. Also gluteus medius, core, erectors
All Cheeked Up publishes general fitness education. It is not medical advice, physical therapy, or a promise that your body will change. Stop any exercise that causes pain and talk with a qualified professional about injuries, pregnancy, or health conditions before you train.
Equipment
Cloth bands that do not roll into a rubber bracelet the moment you get warm. Useful for kickbacks, squats, and lateral walks.
About $34
Equipment
A mat for bridges, clamshells, and knees that would rather not meet the floor directly.
About $40