There are two answers that I can offer, although neither is directly what you're looking for.

The first is that asceticism was extremely important in the Middle Ages, and that this asceticism entailed (obviously when you think about it) an intense focus on the body, its appetites, and its limits. When you're starving yourself in a cell in the Egyptian desert or living on top of a pole for 40 years it's something that you're going to think about. The subduing of the bodily passions was taken to be an ideal and understood, although the direct linkage is often somewhat implicit, to lead to a sort of renewal of the body, prefiguring the resurrected body of Christian eschatology. The Life of Antony (not medieval, but tremendously influential, and see the middle for some ideas about the relation of body and soul which informed centuries of monasticism) gives an example of this when Antony is walled up for almost 20 years and emerges healthy, not fat, not thin, not lean, but as a sort of perfected mean. Ascetics were also understood to be able to perform tremendous feats, both physically -- see the aforementioned Symeon -- and miraculous -- see basically any monastic saint's life. However, I'm not sure that there were any specific bodily movements/positions that such a life mandated (besides perhaps prostration in prayer and bowing, see Symeon again).

However, there were specifically bodily movement prescribed for those participating in the liturgy, and these movements were understood to have a deep metaphysical significance. Thus, this gesture recapitulated moment X of salvation history, while that gesture recapitulated movement Y, and a third movement signified the Incarnation, and so on. The best source that I can think of for this is Honorius's Gemma Animae, which is unfortunately only available in Latin. These didn't really constitute a "discipline" a la yoga (at least in my limited understanding of yoga) but get you somewhere close I think.

Oh, I should add that the classic source on this topic is Peter Brown's Body and Society

This is really a secondary question disguised as a comment, but... I've read about stadhagaldr, an ostensibly old (pre-Christian?) practice that's also called "rune stances," related to a Viking/Nordic martial art called "stav" that has supposedly been passed down for 44 generations through the Hafskjold family.

The idea is that you model your body on the shape (or esoteric meanings) of each of the 16 runes of the younger futhark, something a lot like baguazhang's relationship to the bagua, the eight trigrams.

Now, these are claims, and I've only seen them made in the context of practitioners of a reconstructionist belief system. The structural resemblance to bagua makes me think it sounds reasonable, but....

I'd be really interested to hear an academic opinion on stav and rune stances.