Q: If someone does things to strengthen to become more fit for the spiritual work, do these acts become spiritual acts, if that is the purpose of keeping fit?
A: During the twelve years that I served as personal secretary and assistant to Rabbi Baruch Ashlag, I regularly went swimming with him, or on walks in the park or went with him to a gymnasium. He was between the ages of 75 and 86 at the time! He made great efforts to keep physically fit so that he could lead and accompany dozens of young students. Moreover, we took voice lessons so that he could talk for hours nonstop, without fatigue or hoarseness. Something that is needed for the spiritual work is indeed considered a part of it.
I hope that you can clearly discern your true motivation for your choice of physical activity, so as not to portray the desired as the actual. You can do what you like in your physical activities, but whatever you do, refrain from any kind of meditations and thoughts.