I’ve heard the research cited several times but have never bothered to locate the precise source.
Resources
It amount to hearsay; inadequately information with no support. It may or may not be true.
In situations like that you need to drill down and find research and/or empirical data from various sources.
I don’t agree that an experienced coach’s guesstimate is useful in any scientific way.
What You Can See/Feel
A good coach that has been around knows Power when they see it.
Car Example
The majority of people know the different between a car going 30 mph and 50 mph when they see it without using a radar gun.
The feel of going 30 mph is different than going 50 mph.
Power Factor
I have an inexpensive devise that measures Power Output. It amount to having some cheap scales. The cheap scales will give you and idea of you body weight that is within a few pounds of a good set of medial scales.
In performing Speed Jump Squat years ago, I experimented with the various Speed Training Percentages; research has demonstrated that 10- 40% of 1 Repetition Max, with 30% being the "Sweet Spot" for Speed.
What I found was my speed was optimizes with 27% of 1 Repetition. There is a plus/minus factor. However, I was in the ball park.
Ironically, all it did was reaffirm what I felt. As the Speed Training Percentage research stated, I felt that my speed was maximized with a load of around 30% of 1 Repetition Max.
Competition Deadlift
The amount of Power you see a Powerlifter pull a Deadlift on his second attempt provide you with a good idea of what his/her final attempt should be.
I am sure you can "Read The Signs" on a second attempt for someone and determine about how much more they can pull on their final attempt.
...you are making concrete suggestions about basing training weights on kettlebell swing percentages of max
1 Repetition Max
The foundation of Strength Training is built on the Training Percentage "Guidelines" that provide you with information on how to optimize the various type of Strength Training: Limit Strength, Acceleration Strength, Explosive Strength, Hypertrophy...
To reiterate, there no practical way for a lifter to measure or know there 1 Repetition Max Kettlebell Swing.
With that said, anecdotal data obtained by watching others as well as performing Kettlebell Swings with various loads provides the observant lifter/coach with great feed back on which loads (Training Percentages) elicit that greatest amount of Power Output.
Cross Reference
In my previous post, I provide some of my resources on Power Output Training Percentages for Traditional Exercises (Squats, Bench, Deadlft, etc) and for Explosive Movements For those interested, I can provide the research articles on that.
I provide Dr Bret Contreras' research on the load that produce the greatest Power Output with the Kettlebell Swing.
To fully comprehend how to evoke and develop Power Output with the Kettlebell Swing, you need to examines the data on Explosive Training and determine the prime root linchpin which they all share.
I have presented some research information and can provide more for those who might want more.
Kenny Croxdale