Cheat Codes: How To Improve Club Head Speed By Increasing Vertical Force At A Specific Point In The Downswing

Last month, BodiTrak advisor Dr. Sasho MacKenzie joined Cordie Walker on the Golf Science Lab to discuss ground mechanics and the importance of dynamic vertical force in the golf swing.

Cordie does a terrific job producing his podcasts, editing hours of conversation into 30 minutes of insight that is both actionable and understandable. We wanted to put together an article that elaborated on a few of the concepts and illustrations they shared.

Click the image to listen to the Golf Science Lab podcast with Dr. Sasho MacKenzie and Cordie Walker

If you’re reading this, there’s an excellent chance you’re familiar with Dr. Sasho MacKenzie and his work. Sasho is one of the world’s most-prominent researchers in golf – one of his areas of focus being golfer-ground interaction, specifically looking at how golfers can use the ground productively to optimize club head speed.

Through his work, Sasho began to notice a consistent trend among golfers, regardless of handicap: faster swings correlated with the ability to generate more vertical force using the lead foot when the shaft was vertical downswing (SVDS).

At shaft vertical downswing, the magnitude of the ground reaction force under the lead foot was separating [fast and slow swings].
– Sasho

Courtesy of Dr. Sasho MacKenzie, St. Francis Xavier University

Sasho’s research is legitimately ground breaking for the golf industry. Not only does it reveal a contributor to the most desired cheat code in the game – more speed – the correlation was remarkably strong.

When Sasho ran the correlation on four studies he’d performed they came back at 0.84, 0.87, 0.82, and 0.91, respectively. For context, 1.0 is a perfect correlation. As Sasho noted on the podcast, there have been studies about the relationship between delayed wrist release and club head speed, but that correlation is closer to 0.4. 0.82 – 0.91 is extremely high and confirmation of the importance of his findings.

You know there is a relationship there. In terms of trying to come up with things that happen in mechanics and club head speed, that’s very high… It’s a significant thing.
– Sasho

Before we jump into a few illustrations, let’s break down this finding a bit further and dispel any confusion.


No. We want the most possible.

The correlation isn’t evaluating when or what the peak in vertical ground reaction force is. GRF could peak after shaft vertical downswing and it could peak before. Specifically, we’re evaluating the force at one point in the swing. At SVDS, we want this force to be as high as possible. Check out the force and Trackman data of LPGA Tour player Katie Burnett from our article by Daniel Gray. Notice that the vertical force at SVDS in the faster swing was higher than the vertical force at SVDS in the slower swing, but it was not the peak vertical force of either swing.

The point is, at shaft vertical downswing we want [vertical force under the lead foot] to be as high as possible.
– Sasho


Not necessarily. However, if you were to swing a club 10 times, your highest club head speeds would very likely be associated with your highest vertical ground reaction force at shaft vertical downswing.

One of Sasho gifts is the ability to explain concepts through illustrations. Here are a few of his best from this podcast, with our commentary.


If I gave you a sledgehammer and asked you to hit a golf ball with the sledgehammer, there’s a great chance you would lose your balance in your swing. Your center of mass would get pulled over your toes and you’d have to take a step forward.
– Sasho

When we’re swinging a golf club, we have a “learned understanding” of the amount of vertical ground reaction force required to counteract the momentum of the club and keep our body stable.  Though it isn’t a conscious thought, we know that we have to push into the ground to keep from falling forward in the swing. If we handed you a much heavier implement like a sledgehammer, there is a decent chance that on the first swing you would underestimate the vertical force required to maintain balance and would end up falling forward.  As you became more familiar with swinging a heavier weight like a sledgehammer, you’d do more to prepare for the increased momentum by bracing against the ground (increasing vertical ground reaction force) earlier.

This is an extreme example, but it’s a representation of what we’re doing in the golf swing.  Before we even begin the downswing, we begin building pressure under our leg leg (evidenced by a lateral shift in center of pressure towards the target).  Shaft vertical downswing doesn’t represent a peak in this pressure, but it represents a key moment in preparing ourselves for impact.


Even though pulling down on the club should DECREASE the vertical ground reaction force, I’ve learned that even though it doesn’t seem right, I need to INCREASE the vertical ground reaction force so that impact I’m prepared.
– Sasho

What’s most interesting about the vertical ground reaction force at SVDS is that it’s the OPPOSITE of what we’d expect based on our understanding of physics.

As Sasho mentioned, if we were performing a med ball slam on BodiTrak we would actually see our vertical force would decrease. As we pull down on the ball, we’re actually lifting ourselves off the ground. The ball is almost a moving pull-up bar.

This is what makes this finding so intriguing. Vertical ground reaction force should go lower at shaft vertical downswing, but it doesn’t. We’re fighting what would naturally happen.


If you were trying to train a golfer to produce more force under the lead foot you could illustrate it by performing med ball tosses. Try swinging a 10 lb med ball in the same path as a golf club and release it down the target line AND make your center of mass go backwards (away from where a golf ball would be at address). Better yet, do this same drill on BodiTrak.

If you’re able to increase the velocity of your toss and finish with your center of pressure in your lead heel, you know you’ve pushed even harder into the ground with your lead leg. If you did not push harder, you’d either take a step forward or fall on your face.

Anytime you see a video of a golfer swinging of ice you’ll see their lead leg kick forward towards the ball.  This is because they are pushing down and towards the ball with their lead foot, hoping to push the body up and away to counteract the momentum of the club.


At shaft vertical downswing, you’re 0.12 seconds from impact. [Justin James] is probably 0.1 seconds from impact. In 0.1 seconds from now, that club is going to be pulling crazy on you towards the ball. You can’t wait until impact to generate momentum away.

At shaft vertical downswing, you need to start generating momentum in your body away from the golf ball to counterbalance the club pulling you towards the golf ball.

Notice how James’s body is moving up and to the left through impact.

It’s like the sledgehammer example. He’s learned to manage that momentum. – Cordie

In the world of golf science this represents one of the most substantial findings in years, especially as it relates to the study of force and pressure. It seems as if every golfer in the world is in search of more speed. Now – with the right data and application of feedback – you have the cheat codes.