Just wanted to open this for debate. In my experience.. yes. I've played fastpitch and slopitch softball. In my later years playing slo pitch I noticed swinging the bat harder by trying to knock it over fence generally ended up in ground balls and pop ups. Taking a nice relaxed swing resulted in many more home runs. Surprisingly, when swinging hard, even when squaring the ball up resulted in less distance and less home runs. Does loose muscles actually and not swinging so hard as you can actually result in greater bat speed? My DD has a tendency to over swing.