Why We Rethought the Grip for Speed Training

Golfers have been told for years that stronger hands can help them swing faster.

It makes intuitive sense. The faster you swing a golf club, the greater the forces acting between your hands and the grip. So, if you want to swing faster, shouldn't you train yourself to grip the club harder?

At TheStack, we wanted to test that assumption.

What we found changed the way we think about grip strength—and ultimately changed the way we designed our grip.

Is Grip Strength Actually Limiting Your Speed?

To understand the question, we first need to separate grip pressure from the forces that actually accelerate a golf club.

Your hands apply forces to the grip throughout the swing. Taken together, those forces create a resultant net force acting on the club. That net force is what accelerates the club.

And the relationship with speed is remarkably strong.

In our study, 17 experienced golfers swung an instrumented Stack under three different loading conditions: 95 g, 195 g and 280 g. Motion capture and inverse dynamics allowed us to calculate the net force applied to the club.

The 195 g condition is particularly relevant to the golf swing. Although slightly heavier than a typical driver, The Stack is only hybrid length, making the 195 g condition a useful approximation of the overall inertial demands of swinging a driver. We've validated that relationship across thousands of golfers, giving us a reliable translation between 195 g Stack speed and driver swing speed.

Across all three conditions, the relationship between net force and clubhead speed was exceptionally strong:

In simple terms: faster swings are associated with greater net force and this force peaks at impact.

Clubhead speed versus maximum in-swing net force across the three Stack loading conditions. Net force was strongly associated with clubhead speed at every load (r = 0.96–0.98), demonstrating that faster swings are associated with greater force applied to the club.

But grip pressure is something different.

Grip pressure is essentially the squeezing force applied by your hands perpendicular to the surface of the grip. Squeezing the grip harder doesn't directly accelerate the club.

Instead, grip pressure serves another important purpose:

It creates the friction necessary to keep the club in your hands.

So How Hard Do You Actually Need to Grip It?

This became the interesting question.

As the club accelerates, particularly approaching impact, a large force is effectively trying to pull the grip out through your hands.

You obviously need enough grip pressure—and therefore enough friction—to prevent that from happening.

But are golfers anywhere close to that limit?

To find out, we created a second test.

We attached TheStack to a ground-anchored force dynamometer. Golfers assumed an impact-like position and pulled as hard as they possibly could without allowing the grip to slip through their hands. Remember the peak in-swing golfer applied force happens at impact.

That gave us a measure of the maximum force they could apply at the grip.

We then compared that with the forces they were actually producing during a full-speed swing.

The result was striking.

Golfers used only about 50% of their maximum pulling capacity during the swing.

Every golfer in the study was capable of producing substantially more force than they actually produced during the golf swing.

In other words:

Their grip strength wasn't putting a speed limit on their swing.

More Squeeze Didn't Mean More Speed

We also measured grip pressure directly during the swing using an instrumented pressure-sensitive grip.

If squeezing harder were an important mechanism for producing more net force and more speed, we'd expect golfers who generated greater net forces to also demonstrate greater grip pressures during the swing.

They didn't.

The relationship between maximum in-swing grip pressure and maximum net force was essentially nonexistent (r = .02).

Maximum grip pressure showed essentially no relationship with maximum net force during swings with the 195 g Stack (r = 0.02). Golfers who squeezed harder did not apply greater net force to the club.

That's an important distinction.

Grip pressure helps you hold onto the club. It isn't what makes the club go fast.

So What Is Grip Pressure Actually Doing?

If grip pressure isn't what makes the club go fast, why do we need it?

The answer is friction.

As the club moves through the downswing, the golfer applies an increasingly large net force to the grip. The animation below shows both the net force applied to the club and the golfer's grip pressure throughout a full-speed swing.

For context, this golfer swung the 195g Stack at 108 mph. Based on the relationship we've established across thousands of Stack users, that's equivalent to approximately 118 mph of driver swing speed. So, this is a very fast golf swing with substantial forces acting at the grip.

 

 

The purple arrow represents the magnitude and direction of the net force applied by the golfer to the club, while the dashed line extends its line of action. As the club approaches impact, net force increases dramatically and reaches its maximum of ~120 lbs at impact. Late in the downswing, the majority of that force is directed along the grip. The golfer is effectively trying to pull the grip off the club. In this case, that pull force peaks at 120 lbs.

At the same time, the animation reports the golfer's grip pressure as a percentage of their maximum squeeze.

To establish that maximum, we used an instrumented grip containing 96 pressure sensors. Before swinging, the golfer squeezed the same grip as hard as possible. The pressures recorded across all 96 sensors were summed to establish that golfer's maximum grip pressure.

During the golf swing, those same 96 sensors recorded pressure continuously. At every frame, we summed their measurements and expressed that value relative to the golfer's previously measured maximum.

So, when the animation displays 40% grip pressure, for example, it means that the combined pressure measured across the entire grip at that instant is 40% of what that same golfer produced when asked to squeeze the grip as hard as possible.

This gives us a way to watch two things simultaneously:

How much force the golfer is applying to the club—and how hard they're squeezing the grip to maintain their connection to it.

The animation gives us a detailed look at the 195 g condition approaching impact, but pulling back to look at the golfer's entire swing—and at different Stack loads—reveals something else important.

The figure below shows grip pressure throughout the entire swing for the same golfer shown in the animation. Each curve is the ensemble average of three swings at a different Stack load: 95g, 195g and 280g.

Grip pressure throughout the swing for the golfer shown in the animation. Each curve is the ensemble average of three swings at the indicated Stack load, expressed as a percentage of the golfer's maximum squeeze.

The differences between the three conditions are revealing.

With the 195g Stack—the yellow curve and the same condition shown in the animation—grip pressure peaks at approximately 40% of the golfer's maximum squeeze. But this golfer was clearly capable of squeezing considerably harder. When the Stack load increased to 280g, grip pressure immediately increased, peaking at nearly 50% of maximum.

In other words, the relatively modest grip pressure in the 195g swing wasn't because the golfer couldn't squeeze harder. When the task demanded more grip pressure, they produced it.

The 95g condition provides another interesting contrast. The golfer swung the lightest Stack load the fastest, yet did so with the lowest grip pressure of the three conditions.

So, across these three conditions, we see the golfer naturally regulate grip pressure according to the demands of the task. A heavier Stack produces substantially more grip pressure. A lighter Stack can be swung faster with considerably less.

And across all three conditions, the golfer remains well below their maximum squeezing capacity.

And that's where things get particularly interesting.

From a purely frictional standpoint, you might expect grip pressure to continue increasing as impact approaches. The pull along the grip is getting larger, so squeezing harder would create more friction and provide greater protection against the club slipping through the hands.

But that's not what happens.

Grip pressure peaks before impact and then begins to fall—even as the net force applied to the club continues increasing toward its maximum.

That creates an interesting biomechanical trade-off.

The golfer needs enough grip pressure to create the friction required to securely transmit force to the club. But continuing to squeeze harder also requires greater muscular activation and can increase co-contraction through the hands and forearms, which is not helpful when you're trying to speed up the club late in the swing.

So, just as the mechanical demand for grip security is becoming greatest, the golfer appears to do something seemingly contradictory:

Grip pressure begins to ease while the force being transferred to the club continues to rise.

That observation led us to a different way of thinking about grip design.

Instead of asking:

How can we help a golfer squeeze harder?

We asked:

Can the grip itself provide more security, so the golfer doesn't have to?

That's a very different design problem.

When you're making an all-out speed swing, the forces trying to move the club through your hands are substantial. Even if you objectively possess more than enough grip strength to hold onto the club, the perception that it could slip can encourage you to squeeze harder.

That increased grip pressure can mean increased muscular activation and co-contraction through the hands and forearms—exactly the kind of unnecessary tension we don't want when the goal is to produce an unrestricted, high-speed movement.

So we changed the shape of the grip.

Introducing the Stack Speed Grip

The most obvious feature of the new Stack Speed Grip is the pronounced flare at the end.

We call it the Speed Flare.

Rather than relying entirely on friction between your hands and a conventional cylindrical grip, the Speed Flare provides a physical barrier against the grip moving through your hands.

There's an obvious mechanical benefit.

But we think the perceptual benefit may be just as important.

You can feel that the club isn't going anywhere.

That security allows the golfer to focus on swinging fast rather than holding on tight.

Designed to Let You Swing Fast

Speed training presents a unique equipment-design problem.

You're deliberately trying to swing faster than you normally would. You're training across different loads. And you're repeatedly being asked to produce maximum-intent swings.

A grip designed for that environment shouldn't simply be copied from a conventional golf club.

It should be designed specifically for speed.

That's the thinking behind the Stack Speed Grip.

The research told us golfers don't need help squeezing harder.

They need a grip that gives them every reason not to.

And that's what we designed.

Learn more about Speed Training with TheStack.