You failed to read the “Method for estimating maximum permissible load weight for Japanese native horses using accelerometer-based gait analysis” abstract on the National Center for Biotechnology Information website?? (It’s on our NickerNews Links page)
In fact, one of the BestHorsePractices goals is to read that stuff, pull relevant information from it, and translate it to normalspeak.
The study confirmed what we’ve already learned about the impact of Rider Weight but made another point, too. It’s a point well-articulated by Nikaline Iacono and others in the comments of that article.
All other things being equal, balanced and able riders tax horses less than unstable, un-agile riders.
Here’s the complete Japanese study, with some fun and interesting historical notes, study in pdf form. (And, really, it’s not too tough to get through.)