SEX SPA is a One-Day Wonder that scores very high in arousal value. I suspect many a storefront audience member went home satisfied after watching this baby back in '71.
Format is quite simple: weight-loss and fitness treatments are delivered in the form of sex: following the old saw that "it burns calories".
Frequently teamed Suzanne Fields, Andy Bellamy, Keith Erickson and Ric Lutze pair off for the treatments, with my personal fave Andy scoring highest marks. She and Erickson have a sex scene that is classic -it is interrupted half-way through for them to watch Lutze & Fields to "see how it's done", and then they continue, resulting in a classic blow job and slo-mo ejaculation in tight closeup.
Upon returning home from the spa, there's an orgy adding Nora Wieternik (Fields' frequent co-star, notably in FLESH GORDON) for variety.
For the DVD reissue, After Hours Cinema removed the original soundtrack and substituted a Nick Millard score from ROXANNA and other of his films issued by the home-video label.
Bellamy was always just the slightest bit overweight, so her casting here is astute. I still don't know why her charms are overlooked 40 years later, while her constant co-stars Fields and Rene Bond have been anointed as icons.