GEARS Pro Data: Lead and Trail Knee Extension (A1 to A4)

[iacas]

I have 61 swings (29 drivers, 32 irons (two of which are wedges) with full club and body data of men and women Tour players (or former Tour players) in my GEARS system. I've put them all in a spreadsheet and with that, I can plot a number of things against each other. I'm open to soliciting and creating charts that show you any of the data.

In each of these topics, I'll present the data in a chart of some kind and share the data in the quartiles (min, 25th, average, 75th, max) as well as the standard deviation.

Here's one such chart showing the lead and trail knee extension from address (A1) to the top of the backswing (A4) for drivers and irons:

The plot above shows the lead knee extension (x-axis) for each player against the trail knee extension (y-axis) for each player. Irons are in purple, drivers in blue.

In both cases, "knee extension" is measured as the difference in the bend angle from the starting point (address, A1) to the change of direction of the club shaft (top of the backswing, A4). Positive numbers indicate extension, negative numbers indicate flexion.

The charts below show the independent min, max, quartiles, etc. In other words, the low lead knee extension may not be the same player with the low trail knee extension.

Irons	Lead Knee	Trail Knee
Low	-21.45°	-4.89°
25th Percentile	-16.22°	2.56°
Average	-13.80°	4.82°
75th Percentile	-11.68°	8.17°
High	-0.23°	12.31°
Range	21.22°	17.20°
Std. Deviation	4.14°	4.42°

and

Drivers	Lead Knee	Trail Knee
Low	-26.14°	-10.85°
25th Percentile	-18.26°	0.92°
Average	-15.70°	3.87°
75th Percentile	-12.81°	8.78°
High	-7.03°	11.69°
Range	19.11°	22.54°
Std. Deviation	4.66°	5.82°

If you'd like to request some processed GEARS data, please send me a DM.

P.S. Of the 11 swings where players added flex to the trail knee from A1 to A4… five are irons. Three of those five are women and one of the two men is Mike Weir (and the other is Rory McIlroy). Of the six driver swings, two are women, Mike Weir and Rory are again among the men, along with Jon Rahm and Dustin Johnson. Rory McIlroy, I'll note, squats a bit during the late backswing, and so these numbers are not measured by maximum extension but by what the knee flex is at A1 and A4 only. Women are currently only nine of the 61 swings from pros in the list.

[Phil McGleno]

I am a little surprised at the numbers who increase flex in the trail knee.-Do you have Rory at the max extension in the backswing as I think his squat is skewing the number for him.

[iacas]

1 hour ago, Phil McGleno said:

Do you have Rory at the max extension in the backswing as I think his squat is skewing the number for him.

Yeah…

17.24° at setup, 13.97° pretty close to A2, 18.53° at the top.