Muscle soreness after a heavy workout is actually not caused by the buildup of lactic acid, completely debunking a pervasive fitness myth that has been aggressively repeated by gym enthusiasts for decades.

A closer look

Muscle soreness after a heavy workout is actually not caused by the buildup of lactic acid, completely debunking a pervasive fitness myth that has been aggressively repeated by gym enthusiasts for decades. Lactic acid is actually a crucial temporary fuel source that your body flushes out within an hour after exercise, meaning that the agonizing stiffness you feel two days later is entirely due to microscopic tears in your muscle fibers causing delayed onset muscle soreness. Your body is deliberately flooding those tiny internal lacerations with inflammatory cells to rebuild them thicker and stronger, which is a brutally painful process that makes sitting on the toilet physically impossible. It is pretty hilarious that millions of people foam-roll their quads into oblivion trying to squeeze out a non-existent acid, when in reality, their muscles are just violently punishing them for randomly deciding to do squats after six months of inactivity!