I've compared some sports theme dolls

The full title of the playset is #7420 Olympic Gymnast Set for Barbie and PJ.
No, I don't understand the spinner either.

SunSet Malibu/Gold Medal PJ in her original swimsuit,
Free Moving PJ in #7424 Regatta on the Sea
and Ballerina Barbie in #9658 Mix N Match Set

This article is about two different but related topics:  three similar gym outfits, and the PJ Gymnast Set.

The first half pictures three outfits that are easy to confuse.  The 1975 Gold Medal Gymnast PJ original outfit, 1975's #7424 Regatta on the Sea, and 1976's #9658 Mix N Match Set.  The photo shows Gymnast PJ in part of her original outfit, Free Moving Barbie in Regatta and Ballerina Barbie in Mix N Match.  I don't own the gymnast bodysuit, just the Olympic swimsuits.  The difference is that the bodysuit has a high collar but the swimsuits have a regular open collar.  I also don't own the bikini pants to Mix N Match, so Barbie is wearing the yellow slacks from Regatta.

The second half features the PJ Olympic Gymnast Set.  You could get this set with or without PJ; I have the one without.  It is one of a few PJ gift sets sold over the years.  The front of the box is a photo of PJ performing and the back of the box shows some of the poses you could supposedly do.  I don't have the spinner thing, so I cannot tell you about it, but I do have the gauntlets (I guess that's what they are called) to hold the doll on the bar.

You have to put the gauntlets on the doll first, then slide them over the bar, then hang the bar on the towers.  It's almost impossible to put a doll in the gauntlets if you place them on the bar and tower first.  Getting the bar to slide between the gauntlets is difficult and you will have to forcibly bend the doll's thumbs or hands to complete the job.  The SunSet Malibu and Free Moving dolls of 1975 have different arm and hand arrangements and neither type of doll is easy to get onto the bar.  I also tried the 1976 Ballerina Barbie and her hands and arms don't allow the bar to slide in at all.

I couldn't get either a Free Moving or Malibu doll to do all of the poses on the box back; the dolls are simply too stiff, even with bendable legs and soft vinyl arms to get into position.  So I am demonstrating what I WAS able to do with the dolls.

Maybe the dolls were flexible enough to do these pose
in 1975, but they aren't now.

Hanging upside down is a good way
to straighten your back and clear your head

Barbie prepares to hang from her legs.

Next step is the hardest:
Sliding the horizontal bar past the hands.

PJ looks ready to do chin-ups!

I guess the horizontal bar could also be used as a dumbbell?