Squeeze your fist as hard as you can and hold it. Within a minute, your forearm will start burning even though your hand has barely moved.

That is part of the problem with grip strength in BJJ. Many gripping exchanges rely heavily on sustained isometric tension: your forearm is working hard while your fingers appear almost still.

And that is why your grip often dies not simply because your hands are weak, but because you are holding more tension than the position requires – for longer than necessary.