Thank you for your reactivity @JuanFMontesinos JuanFMontesinos. I have a better understanding now. In my case, I assume that the model is at its best performance, it was trained on a big dataset for body joints estimation. However, when I’m doing Inference on my own very specialized data (with weird humans body poses), it doesn’t do well.
So, if I’ve understood what you said, I should load my model as a pre-trained model and redo training on my own data?
Can you confirm?
Now if yes, should I set  requires_grad = True on the parameters of my model ?