@swimgym_com: Are you making this butterfly mistake? When swimming butterfly, you challenge your core muscles to keep your body stable as your arms and legs move simultaneously. You also work your arm, chest and upper back muscles to raise both of your arms up out of the water and over your head. Your body’s position during the butterfly also helps improve overall flexibility. That’s why you should swim the butterfly stroke. #Swimming #swimgym #swimlife #swimrun #swimbikerun #openwaterswimming #swimmeme #swimmemes #swimcoach #swimtraining