I took this one from sprinters.
If you are doing work that can be potentially taxing on the CNS (heavy lifting, explosive work, going to failure) one way of reducing excessive CNS demands is to focus on keep everything from the neck up as relaxed as possible. This will prevents an excessive CNS “jolt” that can indeed boost your performance, but also make you hit the wall really fast.
Tensing the face, clenching your jaw, having your neck look ropey CAN increase force production and is a tool that can be used when competing or maxing out. But it comes at a cost and that cost is that your nervous system will take a lot longer to recover and you might even end up suffering from “workout hangover” the next day.
If you focus on keeping everything from the neck up relaxed during training (training is not testing and it’s not competing) you will be able to recover much more easily from your workouts and will be able to train more often.