Speed is essential to a good shot. Other factors remaining constant, it is what sends your ball "flying". The average amateur golfer swings at about 90mph and sends the ball around 220 yards. In contrast, professional golfers swing at an average of around 113mph and their shots can reach over 290 yards. Considering these, speed is clearly a critical factor when it comes to distance.
Many golfers, to get more distance, tend to hit the ball harder. But that’s tension, not speed. Your shots will be more precise and fluid if you don’t let
tension get in the way. By focusing
on smoothing your movements, you’ll find your golf swing will become more
consistent which provides greater accuracy and distance.
For a faster, more fluid swing, you need a stable base. On a treadmill, walk backward to strengthen the backs of your back legs. To exercise your shoulders, press your palms straight in front of you and pinch your shoulder blades together for a few seconds. Stronger shoulders and legs will help provide more club speed without sacrificing control.
Improving your grip will also help fix some speed issues. When the club is already positioned parallel to the ground, a weak grip means poor control. If you hold the club more securely, you can make your shots more precise while increasing your club's speed.
To practice speed, use a shaft or alignment rod and swing five times right-handed and another five left-handed as fast as you can. Repeat using a 5-iron and then a sand wedge. After swinging right-handed and left-handed with all three items, shift to your usual stance and repeat the exercise. This will help you swing faster and more fluidly.
Increase Your Swing Speed, GolfDigest.com