When many unbroken strength records were set
Used today in many of the best training centres around the world
Cheaper to make and easier for teens and female gym users to hold
Thicker handles stimulate much more muscle activation in the hands and forearms and in the upper arms and whole upper body. More muscle activation means much bigger muscle and strength gains.
Thick bars spread the weight over a larger area of the hand (just imagine bench pressing with a thick bar compared to a standard skinny bar). Many trainers credit this with making training safer and less likely to cause injury. They also make the forearms extensors (the muscles on the top of the forearm) and forearm flexors (the muscles on the bottom) work more evenly which can help avoids imbalances, weaknesses and injury.
Thick bars make your hands, fingers and forearms so much stronger that your body can finally stop "holding back" the strength and muscle gains in your uppers arms, back and chest.
Thick bar training automatically trains your hands, fingers and forearms at all angles. If you are bench pressing, the thick bar will train your hands and forearms in a completely different way than if you are doing chin ups with a thick pull-up bar.
Thick bars perfectly replicate the natural function of the human hand – lifting heavy, awkward objects.
Thick bars means you are training your grip the whole time and you don't even need to do any extra exercises.
Thick bars are harder to handle so you need to concentrate a lot harder. Some credit this alone with making them significantly stronger.