Good neural control, specifically the ability to independently contract and isolate a muscle to the point of mild cramping, is a predictor of potential for increasing that muscle's strength and size.

“And this what I call the Cavaliere test, which is at least if I could paraphrase, so for instance, if I can, it's always the bicep, isn't it? Let's use the calf or the bicep. If you can flex your bicep to the point where it hurts a little bit, like it almost feels like a cramp or a cramp, where you can flex your calf to the point where it really cramps up a little bit, almost feels like it's nodding up, that's a pretty good indication that you're going to be able to stimulate that muscle well under load if you're doing the movement properly.”

“if you can contract a muscle very hard to the point where it almost feels like it's cramping, if you can do that even when there's no weight in your hand or there's no resistance against it, so you're just using your mind muscle connection to contract that muscle hard and isolate it, chances are you'll be able to generate hypertrophy and strength gains pretty easily in that muscle compared to muscles that you have a harder time activating.”

“If you can contract a muscle very hard to the point where it almost feels like it's cramping if you can do that, even when there's no weight in your hand or there's no resistance against it so you're just using your mind muscle connection to contract that muscle hard and isolate it, chances are you'll be able to generate hypertrophy and strength gains pretty easily in that muscle compared to muscles that you have a harder time activating.”