Set-up: Grasp a dumbbell or kettlebell with two hands across the top. Make sure you can handle the weight securely, and bring it in front of your chest. Do not round the lower back while getting the weight into position - keep your torso tight and braced.
Movement: Step forward onto your heel, keeping your knee behind and in line with your toes and your hips level. Brace through your stomach and do not allow your lower back to round. Descend until just before your knee touches the floor. Then - pressing through your heel and not the toes - step forward, bringing the other leg through and repeating the motion. Keep the dumbbell secure in front of you and use the muscles of your core to maintain stability.
Repetitions: When both legs have completed one full step, this counts as one repetition.