Set-up: Begin by grasping a kettlebell with one hand and bracing through your abdominals and core musculature. Drop your hips and let the kettlebell move behind you, starting just in back of your heels.
Movement: Keeping a tight brace through your core and a strong grip on the kettlebell, drive through your hips - swinging the kettlebell upwards until your arm is parallel to the ground. Look forward and keep your arms straight, squeezing through the glutes both for drive on the way up, and stability at the top. At the top of the range of motion, switch the kettlebell to your opposite hand. Return to the start under control, being careful not to round or hyper-extend the lower back.
Emphasis: Don't shrug your shoulders or flex your elbows to attempt to extend range of motion - the hips should drive the movement.
Repetitions: Each swing counts as one repetition; once both arms have swung that will count for two repetitions.
Muscle Roles in kettlebell alternating swings single-handed