You have agreed to help mommy start working out. she comes to meet you all ready to go in her workout gear before quickly noticing how HOT this room is! no ac or fan??
you inform her the best way to workout is in a hot room where you can really sweat... and to do it all naked.
mommy agrees and strips down before quickly stretching then hopping on the treadmill. you watch mommy work up a sweat in a couple angles. after she's dripping it's time to hop off and do some more exercises (some she's WAY more comfortable with others) all while you watch as her sweat keeps picking up.
by the end when mommy is finally hopping off the bike, you are visibly fully hard. mommy encourages you to stroke yourself here to her sweaty body as she shows it all off , ending in a cum countdown.