Well, Baobeir, nice job on your looser and light sketches of the figure studies.
Say, to help yourself up your game on your quick sketching in motion of the figures, would you please look up some Michaelangelo and Rembrandt master drawings online on DuckDuckGo, bookmark and reading list them, then download them one-by-one, and to make 30 minutes of 30 second quick warm-ups of them? (60 sketches)
The reason why you would do this idea to improve them is because, you'd be able to figure out, for yourself, on how those guys made their drawings more dynamic, energetic and fluid.
Good luck, and I hope you've found this concrete.