According to TrackMan statistics, the average 7-iron clubhead speed on the PGA Tour is 90 mph. The average male recreational golfer, on the other hand, swings the same club at closer to 75 mph, which is why he hits his 7-iron about 140 yards, compared with 170 to 180 yards for the Tour guys.
One reason amateurs generate so much less clubhead speed is that they try to hit "to" the ball rather than "through" it. The fastest part of your swing should occur after impact, not before. If this sounds like your problem, here are two drills that can help get your speed in the right place and create faster clubhead and ball speeds.
DRILL NO. 1: COIL AROUND A CHAIR
Find a chair that's about as wide as your stance and straddle it so you feel some pressure on the insides of your legs. Take your normal address position with a 7-iron and turn your shoulders slowly to the top until you can't turn them anymore. The chair will keep you from turning your hips, which will allow you to feel the sensation of coiling your upper body against your lower half.
The more tension and resistance you create this way, the more potential energy and clubhead speed you'll create in your downswing. Practice this drill several times a day for a few weeks, and you'll soon find yourself wielding a powerful slingshot motion through impact.
Do you gasp a little every time you hear that a Tour player has pulled a 7-iron to hit a ball that's 180 yards from the green? The pros achieve that kind of distance by hitting through the ball, not to it. Straddling a chair to keep your hips stationary as your shoulders turn back is a good way to get a feel for the proper power-generating resistance you need in your swing.
DRILL NO. 2: LEAD WITH YOUR HIPS
Hold a 7-iron across your shoulders and make a full shoulder turn to the top. As you start down, picture the spot on the ground where the butt end of the shaft is pointing as you reach the top, then bump your left hip forward without moving the grip.
This will help get your hips, rather than your shoulders, started first, and this will allow you to create greater separation between your hips and shoulders and retain more of the coil created in your backswing as you swing down. That's how you generate maximum speed after the ball. You want to lead with your hips and turn them as fast as you can from the top while leaving your shoulders in place.
Once you reach the top, bump your left hip toward the target, which will help give your hips a head start over your shoulders in the race to impact. More separation between your hips and shoulders in the downswing means more power transferred to the ball.