I tried (one camera) capturing some push-ups. The result was that in ipi the model lifted one leg up to his head and kind of shook.

Are there tips for better results?

Use two cameras. One camera I think can only capture a standing guy with minimal movement.

I recommend that you use more cameras, preferably 3 of them.

In current version, single-camera mode can only do upper body motion capture. Multi-camera mode can capture more complex motions.