I think it was one of the Cher videos (whichever one had the floor aerobics in, not the step). Or it could have been a Jane Fonda.
Now my first home workout of any kind was a record! Vinyl (odd as it seems to me, some people don't know what records are!!). Jane Fonda, or Joannie Griegans, or Bess Motta (I had all of them, plus a couple more).