In my experience, no matter how you slice it, Goju is grounded in strength. Tight, extended contraction of your muscles will give your muscles endurance and strength. Bigger muscles are also denser; and makes it easier to absorb impacts. Additionally, it teaches proper breathing, and at least for me, having mental control to keep all my muscles tense has made it easier for me to do things like block out pain. Just my personal experience. It is a complicated kata. It's been 3 years since I've learned the kata, and by no means is it anywhere close to being what I would consider "decent".