Ran across this - a German track cyclist who’s nickname is ‘Quadzilla’. He regularly squats 280kg (617lbs) and can sustain 70kmh (~44mph) on a bike. He’s old now (39) but in peak shape his thighs measured 34”, bigger than my waist.
There's a world class arm wrestler who has a genetic condition where he has extra muscles in his arms. Not just bigger, but more tendon insertions in the bone. I think he has more fingers than normal too.