I've always been a huge advocate for lunging. In fact, if you spend any time at lakota in the winter you’d probably see me lunging at least one horse a day. There is so much you can work on while you lunge other than just “getting the buck out” or “stretching their legs”. It can really be a vital part in your strength and conditioning routine for your horse.
In the first video you can see I’m lunging Otis with only the bridle, lunge line and whip but in the second video I'm using a rope tool. This tool connects to the bit and runs between their front legs and around over their wither area. I use this lunging aid quite often and for quite a few reasons too.
In the top video, you can tell that without this tool they are more free to do whatever they want with their head resulting in more leaning on the lunge line, tracking their shoulders out or in, and not keeping their hind end underneath themselves on the track that you’ve set with your lunge line.
In comparison you see in the bottom video that adding this tool encourages them to keep their head down and neck straight thus making it easier for them to engage their hind end properly on the circle. Resulting in them using their body more correctly. It also encourages a bit of contact from the bit to the lunging tool which can be helpful to teach horses to accept more contact.
I love this tool because of how soft and non invasive it can be (when introduced properly) but yet how much of a difference it can make in your lunge work.