Who has them? I have been lifting close to 30 years and don't. I'm not small either chest 50"+ and arms close to 19" pumped. I believe it's genetic. Just like women who have kids. Some get awful stretch mars others none. We have 5 kids with another on the way and my wife, 5'-2, 105 lbs to start doesn't have them and she gets up to 155 in 9 months which is almost a 40% weight gain and 50% gain around her belly.