Which arm move works your biceps more: slow Tai Chi or fast fly?

Changing how you perform resistance exercises, such as squats or bench presses, changes the amount of mechanical stress applied to the muscles being worked.

When healthy young men perform an elastic band reverse fly versus a Tai Chi-style elastic band movement, the reverse fly generates more force at the shoulder and activates the back of the shoulder muscle more strongly, because it involves wider arm movements and faster motion.

When healthy young men perform a Tai Chi movement with an elastic band, their shoulder joints move more slowly and steadily than when they perform a reverse fly motion with the same band.

When healthy young men perform a specific Tai Chi exercise with an elastic band, it activates the infraspinatus and coracobrachialis muscles more than another elastic band exercise called the reverse fly, which activates the anterior deltoid and subscapularis muscles more.

When healthy young men perform a specific Tai Chi movement with an elastic band, they generate more force at the elbow and activate more muscle fibers in several arm muscles compared to performing a reverse fly movement with the same band, because of differences in how the joints move, the speed of motion, and hand placement.