
The one arm dumbbell fly is a unilateral variation of the dumbbell fly. It is used by those who would like to focus on one side of their chest working at a time.
When performing the one arm dumbbell fly, it is important to start off with the weaker side of your chest. While the pec you’re not working will be recovering while performing the one arm dumbbell fly, it makes sense from a conditioning standpoint to work the weaker side first.