Tension feels like effort. It's actually brakes. Bolt's face is loose, his hands soft. The man grinding beside him — jaw clenched, fists tight — is losing.
Your muscles work in opposing pairs. Clench both and they fight each other. You burn enormous energy pulling against yourself and go slower. Grip a fist while sprinting and your time drops.
Elite athletes remove interference. Peak performance isn't maximum effort. It's maximum output with minimum resistance.
The tightest person in the room is rarely the most effective. Clenched jaws, white knuckles, gritted teeth — that's not intensity, it's friction. The people who move fastest through hard things have learned to stay loose inside the effort.