The kettlebell row exercise is a compound strength exercise that targets your lats (back), delts (shoulders), biceps, and triceps. Doing this exercise on one leg decreases one's stability making the exercise more challenging. This allows you to engage your core muscles to stabilize yourself during the exercise. The bottom pictures are a regression of this exercise and are great for beginners. If the kettlebell row on one leg is too easy, try balancing on a bosu ball while doing the exercise to decrease your stability.
1) Keep your back straight and butt out. Do not arch your back.
2) When doing a one arm row with the kettlebell(or dumbbell), lean forward with one leg stretched out behind you.
3) Place the kettlebell beside your front leg and rest your arm on a bench beside you or on your leg for stability.
4) Lift the kettlebell up and into your body and squeeze your shoulder blade.
5) Repeat on the opposite side
6) Try 3 x 12 of this exercise. You should feel fatigue during the last couple of reps of this exercise.