Evidence for magic number "70% of 1RM"

[djsilvera]

I certainly feel a difference working at weights that are a substantial percentage of my projected 1RM. And I've heard coaches mentioning that the adaptation we're looking for happens when you stress the body using weights (roughly) at or above this threshold. Can anyone point to literature discussing the relative stress and adaptive process that happens above that threshold versus working to exhaustion below that threshold?

[djsilvera]

I should add that I currently tell people that it's probably a hormonal thing, without having evidence for it. Above 70% I "imagine" that I produce more growth hormone/testosterone/happy juices than if I work lighter for high reps until exhaustion.

[John Hanley]

I should add that I currently tell people that it's probably a hormonal thing, without having evidence for it. Above 70% I "imagine" that I produce more growth hormone/testosterone/happy juices than if I work lighter for high reps until exhaustion.

Mechano growth factor production - for one - is sensitive to load vice metabolic stress alone.

Edit: But I don't have pub access.

[Eric K]

Mechano growth factor production - for one - is sensitive to load vice metabolic stress alone.

Edit: But I don't have pub access.

This is why I perpetually underestimate my 1RM. I'm squatting 150% for 3x5. Genius.

[Cody]

Motor unit recruitment threshold. Pretty simple if ya ask me.

[Meshuggah]

70% is too light.

[John Hanley]

The interesting question is "why 70%"? I'm dealing with a lot of empirical-fit models right now at work, and while immensely useful, "why" these things work would be enlightening (in some cases groundbreaking) for dummies like me. I suspect this 70% threshold for strength gains is similar. Sure, it seems implicit from a power law type of function, but describing the mechanisms (well and mathematically) seems to be lacking.

Yeah, I don't know if ex phys wünderkinds are hoarding all sorts of wonderful models, but what reaches us curious genpop peasants is really crappy.

[Cody]

The interesting question is "why 70%"? I'm dealing with a lot of empirical-fit models right now at work, and while immensely useful, "why" these things work would be enlightening (in some cases groundbreaking) for dummies like me. I suspect this 70% threshold for strength gains is similar. Sure, it seems implicit from a power law type of function, but describing the mechanisms (well and mathematically) seems to be lacking.

I'm fairly certain it was mentioned in a short segment of Brooks and Fahey, but it's been a while since I've turned those hallowed pages. Might try to find it tonight for you.

[John Hanley]

I'm fairly certain it was mentioned in a short segment of Brooks and Fahey, but it's been a while since I've turned those hallowed pages. Might try to find it tonight for you.

I've brain-dumped most of Zatsiorsky, but I vaguely recall that the explanation in his opus is totally dated

[John Hanley]

I'm thinking the explanation to this is several ODEs/PDEs, integrals, etc. to get to a numeric solution that approximates the mean (here 70%). i.e. Lots of hard as fuck math to explain the biophysics involved.

Your mathy shit always sails over my head.

I get most of the penis jokes.