OK . . . . stick your arms out from your shoulders parallel to the ground . . . .
Now make your hands move parallel to the ground in a cicle by turning like you were a helicopter. . . . your spine is ONLY required to twist to keep them on that horizontal plane . . .
Now do the same thing only add waist bend to get your helicopter dealie moving on an inclined plane . . . your objective to keep your hands and arms moving in the same inclined plane . . . to do this notice what your hips and spine have to do . . . . there is a lot of stuff going on below your shoulders to keep your hands moving in that orbit without disrupting it . . . and alot of it is hips sliding and spine flexing and extending . . . . on the way back and through.