Unlike our teenage years, we don't have unlimited time to work out. Most of us have to get in and get out of the gym in usually under an hour so we need to be efficient if we still want to make gains.
We know that the hard reps are the ones that are most responsible for making you progress, so getting more of them is generally a good thing. Myo Reps allow you to get more hard reps per set, speeding up progress and decreasing workout time.
Coach Winston covers maximizing the workout stimulus with this simple but challenging technique.