Pound per pound, there's probably no longer hitter in the game today than Justin Thomas. Listed at only 145 pounds, Thomas ranked first in driving distance on his way to victory in the 2017 PGA Championship (328 yards off the tee).
One reason he's able to generate so much power is that he creates tremendous leverage by pushing up off the ground through impact. Thomas posts up so hard on his lead leg at impact that his feet practically leave the ground. This promotes maximum extension and clubhead speed. Here's how you, too, can post up like a champ.
THE FAULT: TOO MUCH LOWER-BODY SLIDE
Many weekend golfers slide their lower body toward the target in an attempt to gain more power. Unfortunately, this forces the upper body to hang back and the knees to collapse, which prevents you from creating any leverage with the ground—you can't push up off the ground if your weight is sliding forward. What's more, your arms tend to get pulled into your body, which keeps you from extending them through impact.
THE FIX: STRAIGHTEN AND POST THROUGH IMPACT
Instead of sliding your legs through impact, push hard off the ground so that your legs straighten and your body weight moves more up than forward. This move is similar to a basketball player going up for a rebound or a standing broad jumper using the ground to explode off his feet. Done correctly, your lead leg will straighten and post up at impact, which will allow your right side to fire through and your arms to extend and swing past your body. This is the recipe for maximum clubhead speed and power.