Body Parts
The cypher for this puzzle is simply an article of clothing with some numbers on it. If the clothes are disposable (or you have washable ink that shows up), you can write the numbers directly on the clothes. Or, you can do as I did in the example below and simply safety pin paper numbers on the clothes so they can be easily removed.
A one-piece outfit like a jumpsuit is nice to use so you can reference the whole body on one outfit, but you could use multiple pieces. It is also nice to use clothes that are a bit oversized for at least some of the players so they can easily wear them. Wearing them is not necessary to solve the puzzle.
The second piece of this puzzle is a document that contains references to body parts like the one here.
The following warm up stretch routine for is a great way to start the morning: Pectoral Stretch (chest), Cobra Pose (abs), Triceps Stretch (arms, left then right).
These two pieces are put together to get a code. The message references four body parts in the following order: chest, abs, left arm, right arm. As you can see from the image above, the jumpsuit has a number on each of these body parts: chest has 4, abs have 1, the left arm has 7 and the right arm has 6. This leaves you with the overall code 4176.