<iframe src="https://player.vimeo.com/video/277196699?background=1" width="640" height="360" frameborder="0" allowfullscreen></iframe>
Beginning (gram on left) – Using no weights, step back to a lunge, then stand with your feet together, then step forward to a lunge.
Intermediate (mom in middle) – Using light/medium weights, step back to a lunge, then stand with your feet together, then step forward to a lunge.
Advanced (me on right) – Using a heavy dumbbell, step forward and back to lunges without stopping in the middle.