Bulging disc, perhaps?

Windmills are where you hold a dumbell, say 50 pounds over your head in one arm, and reach down and touch the floor with the other, then come back up.

scroll down to the middle of both these pages:

http://www.wannabebig.com/article.php?articleid=193

http://www.t-nation.com/readTopic.do...itan?id=459681

helps to have instruction here.