The Relationship Between Lead Leg Force and Early Extension

Jan 13, 2019 | Article, Golf

Early Extension is one of the common swing characteristics in golf. It is also commonly misunderstood. The purpose of this article is to share why early extension occurs by focusing on its relationship to a golfer’s interaction with the ground.

We’ve recently released our updated Golf Ground Mechanics Certification. It’s an extension of the program we introduced in 2016, but offers a more robust curriculum and includes additional insights from the research coming out of Dr. Sasho Mackenzie’s lab.

Below is a clip of Sasho and Mark Blackburn describing the ground mechanics associated with early extension. It’s a 4 minute preview of the 3 hours of content you’ll find in the GGM Certification.

In our opinion, this is among the most clear and concise explanations of early extension that exists.

Understanding concepts associated with ground mechanics is something that every golf coach can benefit from. Without this awareness, your picture of the golf swing is incomplete. For example, telling a golfer to keep their hips back might encourage them to hinge, but as the video showed you, avoiding early extension has more to do with how you’re pushing against the ground.

Watch any clip of a golfer swinging on ice skates. They aren’t just entertaining, they are instructive.

Notice that on the downswing the golfer’s trail foot moves away from the ball and their lead foot moves towards the ball. This is a representation of how they’re pushing against the ground to rotate their hips.

In a golf swing, pulling against the ground with your trail leg will move your hips towards the ball, while pushing against the ground with your lead leg will drive your center of mass away from the target.

Additionally, swinging the club creates momentum which tries to pull your center of mass towards the hall. If you don’t use enough force to counteract it, you have to early extend.

Recall Dr. Sasho MacKenzie’s sledgehammer analogy. If you were to swing a sledgehammer like a golf club, the excessive weight of the sledgehammer would create more momentum than the head of a golf club and tend to pull you over your toes (towards the ball) on the downswing. In order to keep from falling over, you’d need to use more force with the lead leg to counteract the momentum.

If you’re a golfer who early extends, it’s likely that your lead leg is creating less dynamic vertical force than a golfer who doesn’t early extend.

Here are three golfers hitting driver DTL: Justin James, Dustin Johnson and Jimmy Walker.  Watch their hips in the downswing, specifically in relation to the distance from the ball.  Both DJ and Justin aggressively extend their lead leg on the downswing (pushing their hips away from the ball), while Walker’s maintains significant flex in his lead leg through impact (allowing the momentum of the swing to pull his hips towards the ball).

Justin, a long drive champion, creates the most force of the three. He pushes against the ground so hard that it sends hips away from the ball at impact. His hips move into flexion, not extension.

This is something that most Long Drive competitors do… and even train.  Take a look at this drill that Long Drive legend Jason Zuback shared during his presentation at the World Golf Fitness Summit (note: it’s exaggerated in this drill because there is no momentum from the club head).

DJ does the same thing, but it’s less magnified. Watch where Dustin’s lead foot starts at address and where it ends up at impact.

It’s evidence of how hard he pushes against the ground. When we push against the ground, the ground pushes back on us. The aggressive extension of his lead leg builds force under his foot, causing it to pop up and move away from the ball (the opposite direction that he was pushing).

Now look at Walker. By not extending his lead leg, Walker doesn’t create as much force which allows the momentum of his swing to pull him towards the ball, requiring him to extend his hips to maintain balance.

Take a look at his pressure trace.  At impact (~0:33), his knee is flexed and he has >80% of pressure on his lead side.  Had he aggressively extended his knee like Justin or DJ, his foot would have begun to lift off the ground, sending his center of pressure to his trail side.

You can play great golf with early extension, but you can’t have a complete picture of why a golfer is doing it without having an awareness of what’s happening at the ground.  If you’re interested in learning more about how to incorporate ground mechanics in your instruction, visit our certification page.