5. Pec deck (or chest fly)
Here’s the main problem with the pec deck: guys don’t need another exercise to pull their shoulders forward and twist their arms inward—we already spend too much time at our computers and target our chests often enough in the gym. Over time, this pulls our shoulders out of alignment and creates impingements in the joints.
The pec deck yanks your arms backward as you approach the end of the range of motion, and when you relax at the end of the set, which can harm your shoulder joints. Rather than use a machine, stick to free-weight exercises that move in a safe range of motion.
Use these instead:
Dumbbell Flye (shown in the picture above)