I know Fatman
Despite me yesterday achieving a couple of PR's with springs, when I pulled the two oranges out, they still felt pretty much as hard at full stretch. The most important measurements ( apart from the double-length Lifelines 32" ) were the full-span tensions and I paid a lot of attention to the measurements, so there's only two things I can think of.
One I've already mentioned, is the soft handle Lifeline grip biting into the base of my thumbs. Apart from the discomfort, I'm wondering if some energy lines in the hand are being blocked and sort of weakening the arms and shoulders. I've done quite a bit of Chi Kung in the past and I can attest to sudden surges of otherwise unexplained strength which does not seem to be purely driven by muscle effort. I snapped the handle of my 5" good quality side-cutters on the job cutting through telephone cable in one "bite" with some six months Chi Kung training. No grip training. Some Chi Kung movements I performed became very powerful in their own right, with the proper concentration. Now I'm performing similar movements under tension and it could be the constriction on the hands that's making the two oranges seem so hard. They seem easier until I'm about 2/3 through the movement and that's when the tension on the soft handles really comes in.
( I will write a post soon on the Chi Kung training and my opinion on its relevance to this strand-pulling forum. )
The other thing that has just come to me is that with all the full-stretch measurements, the pause at full tension was very brief. The scale took a few dummy go's to get the hang of and would 'beep' right after the expander ( springs or cable ) was held steady, much less than a second. The measurements are otherwise reliable because I did a lot that I didn't write down or average out, in order to make sure I was using the scale properly.
However, when exercising and pulling out to full span, I pause significantly longer than the scale took to make a measurement. I'm wondering if the Lifeline rubber, having been brought to a stop, and for an instant, actually sort of keeps going for a split second and self-increases in tension, "settling in" and making my full stretch seem as hard as the springs. Funny things happen with compounds like rubber, I am told, and that would go with the "live feeling" that trainers report when they use cables.
At the last, it could be a combination of the soft handles and the rubber "settling" into a slightly higher tension after a half second or so, past the scale's measurement time. Tomorrow I will do the FCP's and OHPD's with no pause and see if there is any difference in the perceived tension. Then I will get back to you on it. The problem may finally resolve itself when I obtain the triple grip handles.
This is of course purely speculation. If I was able to obtain a spring scale, which is really what I wanted, all that would have been measurable. Unfortunately I was only able to buy a digital scale, which goes to show that the latest tech is not always the best, although it was prompt and precise with what I was able to use it for.
I certainly still have an open mind on your "sticking point" theory. If you do end up buying some springs, I wouldn't recommend the York, because I think that the 20lbs springs like my Chinese set are more reliably measurable. Hell, just hauling out three Yorks equals 90lbs+. They don't leave enough room for feeling out the tension. Also, at lower measurements, they proved quite erratic so trying to "feel out sticking points" would probably be near impossible. Do I make sense with any of this ?