You caught effortlessly the line of the spine!
A small recommendation: try to draw after de spine line all the basic shapes of the body, for example, triangles, cylinders, spheres...
You also can see examples in "Figure Drawing, Design and Invention (Michael Hampton)" or watch Ethan Becker's youtube channel, he explains the figure drawing with really good and basic shapes!
Good job and continue!
You are continuing to improve I see. Continue your study of hands & feet. Expand your time up to 10" so you can work on the shading of the muscle structure & visible bone structure. The picture of the figure's back, the head is a little too far the right. Even so, it is a very nice back view.
Continue your studies and practice. In the long run, it will all pay off.