The closest relative to the (two-arm/kettlebell) swing, the one-arm swing adds an additional grip challenge and rotary stability component (the ability to prevent rotation). Just like the two-arm swing, use a kettlebell or dumbbell for this exercise.
Because you now bear the weight by only one side of the body, a good one-arm swing can be measured directly by the amount of rotation that doesn’t occur. So do your very best to keep your shoulders square through the movement. Here are the steps to the one-arm swing:
Assume a shoulder-width stance approximately one foot behind the weight you’re using, point your toes slightly outward, reach out, and grab the weight with one arm.
Grab the handle of the weight as close to dead center as possible.
Hike the weight back as you would a two-arm swing while minimizing any twist in your torso.
With the one-arm swing, you may rotate your thumb slightly in (downward) on the backswing to ensure that the weight doesn’t crash into the knees.
When the weight reaches the top of the backswing, snap the hips forward and stand up as quickly as possible to complete the movement.
Allow the weight to float no higher than eye level before reversing and repeating the movement. If you have issues with your back, allow the weight to float no higher than shoulder level.
Remember to keep your armpit tight throughout the exercise. Don’t let the weight pull your shoulder forward.