Flexing a muscle between sets diminishes the weight that can be moved for performance goals but enhances muscle growth and nerve-to-muscle isolation.

“We also talked about in between set contractions the so called selfie effect of people flexing a particular muscle, isolating a particular muscle between sets, just want to mention that would be a terrible thing to do if your goal is performance on sets. So moving a particular amount of weight. That's actually going to diminish the amount of weight that you can move. It's going to enhance muscle growth and it's going to enhance the nerve to muscle isolation of that particular pathway.”