From watching the videos it is easy to see that the female instructors are having a great time. There is ample evidence that the anal and vaginal areas begin convulsing in a slow and rythmic fashion when the orgasm overtakes them. Why is it that the clit does not get too tender to touch when this happens?
This seems to be a turn off for women if it happens after a regular climax, but with DOing there seems to be no soreness or hypersensitivity even with the very high peaks.