Hi Drew. If I understand the question correctly, % 1 RM, well, most programs base it on your ability to do a maximum lift at a certain percentage. Ryan gave excerpts that are extremely credible as to compensations, but most programs don't take that into consideration. For example, ,pst periodized programs will base recommendations on a 1 RM for the lifts. An advanced person can "guestimate", others should actually take a week or so and find their max in the lifts involved. 80% 1 RM means (in most cases) 80% in weight for what you can do for 1 rep. Then you start out at 60% for 4 X 10 or whatever, and progress up to 9's at a higher percentage, then 5's, etc. Yep, it's flawed, but it does gurantee a progression.
I don't doubt that it does give progression, but now you've got my mind thinking... :D
For a 200 pound person squatting a 1 RM of 300 pounds, 85% (using Ryan's values -- thank you, btw) of his body weight, or 170 pounds, would be included in the squat weight making the total 1 RM squat 300 + 170 = 470 pounds.
So a periodization scheme that starts at 80% (based on iron and not body weight) would start you off at 300 * 80% = 240 pounds. When added to the body weight of 170, this makes the 80% 1 RM weight 240 + 170 = 410 pounds. And 410 pounds is 87% of the total 1 RM of 470 pounds.
In the case of 60% of 1 RM, the actual (including body weight ) is 74%. The lower the amount of weight you lift relative to your own body weight, the more skewed the numbers become.
I'm not suggesting the way weightlifters are doing this is wrong since the programs used have been optimized through years of experience, which is vastly more important. And as long as percentages of the 1 RM are consistently based on iron lifted without regard to body weight, I'll go that route as well at some point. I was merely curious to see how the numbers actually stacked up.