Well, the mind is most important, since it is also a capacity of the soul. When you die, it is teh soul and mind that lives on, so it is best to cultivate this as much as possible. However, on earth, or souls and bodies are joined, so what effects one effects the other, so proper care of the body is also good for the ultimate end of the good of the soul and its healthy function while imprisoned in the body. However, depending on one's state of life, it may be necessary to exercise the body to a beyond normal degree.
The soul is not
imprisoned in the body. The soul is the substantial form of the body. The body and soul are one
. The body dissipates at death, but we are reunited at the resurrection of the body to that same body
glorified. This state of separation is not viewed at all as a positive in Catholic teaching, but an extreme negative, as though being lost. The imprisoned body idea in Catholic circles comes most from Plato and from Mani, and is not supported by Catholic teaching. The soul and body are in mutual support, and the soul is the head of the body, but by no means is the body just something that we steer. The body is our very soul made experienceable to other bodies. Christ came and took on a body, which He has for eternity. Our Lady is special because she never had to undergo a separation of her body and soul. And St Paul said, "For we know that every creature groans and travails in pain, even up till now. And not only it, but ourselves also, who have the firstfruits of the Spirit, even we ourselves groan within ourselves, waiting for the adoption of the sons of God, the redemption of our body
" (Rm 8:23).
Perhaps you didn't mean to degrade the body, but I didn't want anyone to fall into this Manichean error.