paperback thriller/horror - New York City runners - blood for youth - powder blue track suits

This book was published in the late 70's early 80's, I think. It was about a group of very fit elderly runners who maintained their youth/health by drinking (?) the blood of people they recruited, including the protagonist whose husband bought into the whole thing. Sort of a Rosemary's Baby vibe. They ran in machine-like unison in powder blue track suits. Why do I think the prtagonist's name was Brenda and that she had a gay male friend? Could be totally mistaken on this.

I think this is The Glow by Brooks Stanwood, published 1979 "SOMEWHERE in the park they run. And as they run, they watch with hungry eyes the young, loving couples -- like the Lawrences -- couples with the glow."

I completely forgot that I posted this query until just now and then I came back here and I found your answer! It is a MIRACLE! Thanks so much. You are my HERO! My sister is totally going to plotz.

Thanks for coming back and confirming it for us!