The
muscles you use to lift your leg partially originate from your
lumbar spine so it is imperative that you maintain a stable core while
doing the leg raise in order to avoid injury.
If
you are having difficulty with this ball exercise, go back and work
on your
leg
raise and make sure you can
hold
it for at least 30-60 seconds without sagging or shaking.
Begin
this exercise with short movement while maintaining control. As
you get used to the movements you can increase the amplitude of leg
movement.
This
is considered a more advanced ball exercise because you are forced
to maintain a stable core while introducing limb movements in several
planes.