What factors influence a player's maximum swing speed?

Is there sufficient data to explain what enables a player to swing a club 95 mph vs. 105 mph vs. 115 mph? (assuming proper swing fundamentals taught by GSA are applied as a control)

Are there measurable differences in:
- How much more ground force a 105 mph swing generates vs. a 95 mph swing?
- How much the height of the golfer (and thus width of the swing arc) matters?
- How much faster the body (or hips) are rotating, comparatively?

Or is it as straightforward as clubhead speed correlating to the TPI medicine ball assessment?

Hope I'm asking the question in a coherent way...

Ed,
This may not be the answer you are looking for but here are my thoughts. Speed can be generated in three areas; lower body; core; shoulders/arms.
Golfers who hit the ball farther tend to use all areas well.

Example would be Jamie Sadlowski who is 5'10" ish and 170 lbs. He can generate club head speed of 150mph +.
He uses all 3 areas to his maximum ability.

TPI tests can show you areas where you may be good and areas you need to work on. Or where you have a physical limitation.
Not necessarily where technique may be poor.

I would recommend to any individual to focus on which areas they may need to improve on and pick drills/videos to help.If they are not sure
they could always post a swing for feedback. Hope this helps.

There are a couple different ways you can look at this. But, as a general rule.

Distance comes from ball speed
Ball speed comes from club head speed in the plane of the swing
Club head speed in the plane of the swing has a strong correlation to ground force in the lead foot at left arm parallel to the ground.

Many golfers improve their distance significantly without changing speed - https://golfsmartacademy.com/golf-instruction/case-study-gaining-distance-quickly/

To answer some of your questions:
While height helps, there isn't a strong enough correlation to have a formula.
I don't have a force plate, so I don't know the numbers myself. One thing I've seen is that getting the club face and path under control frequently frees up better movements that create power.

The TPI tests are decent at predicting speed if you're aware of them. But again, you can have a dramatically different distance for given club head speeds.

Chris, Tyler,

Thanks for sharing those insights!

Interesting questions. I've been doing some training with superspeed clubs. One of the drills they have is basically the Hogan two-step as mentioned in the videos here. When I do this I find it jacks up my swing speed on the radar. I feel a greater stiffness as I plant my lead foot (the second step) towards the target. I imagine this is the force into the ground at left arm parallel to the ground that Tyler talks about. I think this stronger bracing forces more energy out of the body and into the clubhead at impact. I tried priming myself at the range with the two step and my drives were suddenly going much further. The pressure shifts into the back foot on step 1, then the weight transfers forward, but the lead break provides a super stiff break that's similar to slamming on the breaks in the car. If you really wanted your head to snap forward in the car, you'd break about as hard as you could, thus imparting maximum force which transfers up to the head. The same is true for the golf club head.

But I also feel more speed when I can rotate my back shoulder further using my trapezius, thus rotating the shoulders past 90 degrees. Simultaneously then starting the downswing, even as the club is still traveling back. In this manner I can use more torque through my thoracic spine, thus storing more energy for delayed release.

Joel, stepping drills are a great way to add speed. Many amateurs have an idea in their head that they have to use their legs hard like doing a vertical jump, but the amount of force is much lower (about the same force as jogging). The key is the timing of the leg press and the connection of the leg press to the arm movements. Seems like you found that connection with the two-step drill :)

That's interesting Tyler. I guess part of my impression that tremendous jumping force is needed comes from watching guys like Bubba Watson, who seems as though he's stomping so hard into his lead heal that his toes come up and his foot rotates drastically towards the target. Are you saying that's not necessary?

Yes, I think it's easy to get that perspective. But the data shows about 1.5 to up to 2x bodyweight. Think about it, if they were jumping as hard as they can, they would probably get higher than a couple of inches ;) In my perspective, the amount can be trained, but the timing is the more important part.