30 seconds

These look good! I feel they really capture movement and are easily readable

One thing I do see (and I'll admit I struggle with as well) is a lack of planning for space, ie making sure there's enough space for whole sketch to fit, or drawing smaller to let it fit
Practice picturing the pose as its own complete shape, instead of starting with one feature and hoping for the best. A way to do this, is practicing only drawing the silhouette

Very nice! Keep practicing :)

These look great!

Creating little lines to show the movement of the hands and feet will ground these even more. Drawing a line over the eyes to help show the direction of the face would be nice as well. 30 seconds is not a long time to include these things, but if your speed allows, go for it.

Keep putting in the work!