Start by standing with your back straight and your feet apart. Hold a dumbbell in one hand at shoulder level resting it on your shoulder.
Brace your core muscles and step back into a lunge with the leg on the same side you are holding the dumbbell with, while simultaneously pushing the dumbbell up extending your arm up all the way.
Step back to your standing position bring the dumbbell back down to the shoulder.
Do the number of reps on this side and switch to the other side for the same number of reps.