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Is there a ritual or incantation that can help me become physically stronger ?

Perhaps you could consider joining your local cult of physical perfectionism and alchemy of flesh (aka Gym)?

I know I can go to the gym I'm talking about a booster.

There are indeed Spells which help with physical strength. I had some told to me by witch Anais Besova in private correspondence, if I will find my notes, I will let you know.

But what I remember might still be very useful for you. You need to interact with Dark Spirits of Forest, and you must be able to attune to the energy of oak. Energy of Oak can greatly increase you physical capabilities if you are know hot to interact with Oak and Forest Spirits.

There was also a special Prayer to Sun, which should be done during very early morning, while standing on dewy grass. You might improvise given the circumstances which I described.

There was more, but I can't remember now, it is somewhere in my notes and I myself am not into physical strength part. Physical strength grounds you, making it more difficult to interact with Spirits and do any other Magic related stuff. That's why you don't see physically strong practitioners: most powerful of them are very fragile physically.