If I want to work on my horse's top line or stamina then I head them to the hills, water or sand. I lunge them to gain their balance and learn the gaits I want them at that I can't run along side them to teach. I can't run that long and it wouldn't be any prettier to watch than it would feel for me doing it. Lol
I don't have a round pen so it is all done in a clearing in the pasture that is good and level. I do not point the whip at any part of their body. Usually it is facing behind me and is rotated around and to the ground when I need the extra back up to a command/cue I am giving. Then it goes right back into hiding. I will walk them up to me after every 5 or 7 laps and wave the whip all around them and the popping the ground on both sides as well as swirling it around in the air over their head til I get no response. Then its back to working the cues up and down in the opposite direction for a couple of laps til I get what I'm looking for. As soon as I get a couple of consistent laps of picking up the cues without back up then I call it a day for the lunge. I go for another lead rope walk with a few stops, backs, front and back yields before letting them back to being a herd. I do this only with the horses that need some type of training or refresher to gain trust and respect.
If I just wanted to see them run in circles then I would chase them of their round bale and they will run in circles around me until I walk away from the hay. Lol