The usefullness is because it releases the ligs inside you. To illustrate, stretch your flaced dick out and then do a reverse kegel. You should be able to stretch a little bit farther due to the loosening of the ligs. Now do a regular kegel and your ligs (and dick) will contract. Using the reverse kegel in conjunction with stretching exercises give you more potential to stretch . Look up the A-Stretch for a more thorough explanation. Strong abdominals probably do help a little bit.