Credit: cruffsant461 on Civitai

This is a lora for Flux 2 Klein 9B Edit that takes in an image of a guy and makes him more muscular. I trained it on the base model, not the distilled, so the effect looks best on the base 9B model and more subdued on 9B distilled.

I just used the default Flux 2 Klein 9B Edit Base ComfyUi workflow and added the lora load inside the subgraph. Your prompt can just be the single term: muscle_morph , although I've noticed it tends to like to make the person , which you may or may not want. You can add more to the prompt to cue it in that you want the clothing to remain but refitted.