Unfortunately, yes, due to us having no idea how hard people actually push during studies, failure is gonna have a lot of conflicting evidence. I don’t envy you having to write that article but look forward to it greatly!

A study on trained athletes with a lab assistant screaming at them to do more 1 arm machine curls…probably real failure.

A study on total beginners taking squats to failure with no verbal cuing or feedback…could be a 10 RIR and they’re racking it. 15–20 RIR, even (feels weird to type 15–20RIR, that’s like getting out of bed.

It’s also entirely possible that it’ll be different for different muscle groups, and different for different individuals. A study can give us suggestions, and starting points, but a lot of it is individual trial and error.

Glycogen is just logic…interested to hear your feedback actually. If you store about 300g of skeletal muscle glycogen without training, and increase this to 500g with training, and maybe 600g with carb loading as well (due to appetite increases that often occur with higher rep training), that’s 300g extra weight. It’s also ~1–1.5kg of water that comes along with it. This will show up identically to muscle in basically every way, dexa, bodpod, tape measure, whatever. It’ll *feel* different, in my experience, though.

So, 8–12 might be the same as 20–25. It’s entirely possible that they are stimulating similar pathways, and the “under 6 rep range” is stimulating growth through a totally different pathway due to higher tension. I mean…many Olympic lifters ONLY lift in that range and are developed, so it clearly does something.

It may be ideal to do a mix of 1–6, 7–12, 13–20 and 21–40…which sort of takes us back to the bodyweight thing, where it’s hard to do 1–6 for many body parts.

Recruitment will be a wash, as long as failure is close, but there may still be some physiological differences in how growth is triggered, likely via mTOR.