That back of the heel kicking to the gut is quite sexy, and effective. Some tough kicks just about set the stage for me, and I think it has everything to do with adrenaline and her feet. When the adrenals are stimulated and there is something suggestive of something "sexual" like feet are to a foot perv, well it doesn't take much to start an orgasm. Just a little vesicle teasing and wellah. You can do a little vesicle teasing by first collapsing the urethra on the underside of the penis with something like your foot, and stroking back inwards, not out of the guy's cock but inwards towards the prostate gland, and Jesus the orgasm, shortly thereafter.