Polyspheric explained it well. It's a little more than linear. At 68 yrs old I can appreciate his words. Am working on my core muscles issue right now. It's an uphill battle but it is working. As you get older and you try to lift or carry heavy things like we always USED to, we start to compensate with other muscles and the body mechanics are wrong. Then comes stiffness and PAIN. Use it or lose it is so true. Just use it correctly. Exercise and eat well. I backslid and am paying for it now. Working on it as we speak, I just had to own up to not having an 8hr workday anymore. Make 2022 a different year! Good health to y'all!!! Bill