Curling strippers while drinking Guinness
Seriously though... The biggest mistake people make is working the arms too much. Chest & Shoulder exercises work the Triceps while Back exercises work the Biceps. If you overwork your arm muscles, you will not see gains elsewhere. A lot of people split their routine into Back+Bi's and Chest+Tri's. This has worked for decades. Do each at most 2 times per week for great results.
