If you were to do only one exercise to maximize your ability to hit a golf ball as far as you could with any club what exercise would you do? I am asked this question occasionally and from my standpoint and experience as a former World Long Drive Champion trainer and coach who has trained World Long Drive Champions and PGA Tour players, there is no question what my number one exercise for distance is. Full deep squats. This is a very difficult exercise to perform correctly. As a matter of fact the vast majority of all so called personal trainers when asked how to do a correct squat, just simply do not know. I have almost never seen any personal trainer have their clients do squats period.
One word of advice, if you want to hire a good personal trainer hire a former pro athlete or a high-level bodybuilder or powerlifter. At least they should know how to train correctly for the most part. Deep squats work the entire body with the majority of the work emphasis on the hips, gluts, quads, hamstrings and calves (or in another words legs), butt and low back.
In the correct efficient swing, your hips and stomach obliques are your primary power source. You should wind up or coil against a stabil, strong lower body. Then let that same lower body facilitate and start the unwinding or uncoiling. So if you will, the sequence is a stretch and then double stretch unwinding, in a correct efficient move.
When done correctly as Rory Mcllroy does it is a true movement of power and efficient brilliance. In order to increase speed you must stimulate fast twitch muscle fibers. Heavy deep squats are the perfect exercise to accomplish that and when done correctly the safest exercise to that end. Tiger did deep squats while hoisting the barbell in a overhead lockout position so as to activate the core to a larger degree. Also a very good lift. Highly advanced much like a clean and jerk only done with much less weight so as to hold the weight overhead to do multiple repetitions deep squatting. As a mater of fact he did this exercise approximately a hour and a half in the gym I train at before teeing off in the final round when he won the 2013 Players Championship in Ponte Vedra Beach Florida. I was astonished but I thought it may have calmed him as does a hard workout. Worked for him as he went on to win that day. Most people are afraid of squatting but as I stated earlier. Squatting correctly will prevent injury in many ways by strengthening the muscle ligament and tendons surrounding the joints you need to protect. I highly recommend you hire a very competent trainer or buy my DVD and learn how to squat. Then squat 2 times per week for 6 sets 6-10 reps per set. Feel your distance explode.