Jeremy Easterly, the runner-up at last year's Long Drive Championship, was on Morning Drive Friday morning to talk about how he drives the ball so far. This is the video (with Charlie Rymer) from the show, and he talks about a number of things that can affect your driving... but I'm going to focus on one thing in particular.
Please, PLEASE note that Jeremy draws a distinction between swinging hard and swinging fast. When Charlie asks him about the difference, Jeremy says "That's the million dollar question." Then he talks about controlling emotions because when your emotions get too high, you'll tend to tighten up.
This isn't rocket science, folks. It really is about avoiding tight muscles. Ask any martial artist or any track and field star, they'll tell you that tense muscles move much more slowly than relaxed muscles.
Now, I'm not talking about being some kind of limp noodle when you swing. It's just that you want to stay as relaxed as possible while making your swing. You want to avoid clamping your jaw tightly; you want to keep your back muscles as relaxed as you can; and if your forearms feel like you're locking your wrists, you're just losing clubhead speed.
Many players don't believe how far some of the old hickory players hit the ball, but it's not too hard to understand. My studies of the classic swing show that, because hickory shafts were so soft, those players didn't have to use strength to load the shaft; their focus was on how to keep those soft shafts from loading too much. Because of that, they could stay relaxed and were able to focus on simply swinging their clubs FAST. (Yes, they used slight technique differences to make that easier to do, but those differences weren't as dramatic as you might think.)
If you avoid tensing your muscles any more than you have to during your swing, you'll find that your tempo and sequencing are much better as well. Tensing your muscles more than you have to simply interferes with all the good things you want to do when you hit the ball.
Here's how you can start practicing it: Simply go out in your backyard and begin making those slower, relaxed "practice swings" you usually make before you hit a shot. Gradually try to speed up them up without letting your jaw, back and forearms get tight. While there are other drills you can try, this is something everybody can do and it's just as effective.
Learning to swing fast without getting overly tense, like any other skill, is just a matter of practice. Try the practice swing routine for a few minutes each day, and I can almost guarantee you'll be able to tell the difference within a month. Because moving around without being overly tight is something we humans do all the time. You'll be surprised how fast you'll be able to swing if you just practice a little.
It's simply a matter of learning that a golf swing is just like any other movement. All you have to do is get used to thinking of it that way.