Can’t figure out how he was able to hold/maul so many fighters during his career, some of which looked bigger/stronger than himself. Did he just have exceptional upper body strength or what?
I think it was moreso him being used to this style of fight - while a lot of his opponents were not. He was more comfortable with it and probably developed a bit different, more wrestling-type strength. Andre Ward and even Floyd Mayweather were always looking strong in the clinches - even though I very much doubt it would translate into weight room. Ruiz was likely similar case. Then a lot of it was his conditioning also. You need to be in shape to fight like that.