Load the trap bar stupid heavy and just go for a walk.
Stand fully upright the whole walk. A heavy trap bar tries to round you, don't let it.
Deadlifting a loaded trap bar and simply walking makes the traps hold everything up, carrying serious weight through the shoulders for every second of the trip, while the forearms fight to keep the grip and the core and back muscles lock your torso bolt upright against a bar that wants to fold you. The frame keeps the plates balanced around you, so you can load far beyond what dumbbells allow. It earns its place as the simplest heavy carry there is, brutal, functional and nearly impossible to do wrong with an honest posture.
Load and balance. The trap bar centres the weight around your body and lets you carry loads no dumbbell rack goes up to, without the bells bashing your legs. Dumbbells challenge each hand independently, the trap bar lets you go properly heavy.
Common recipes are 20 to 40 metre trips or 30 to 60 second carries, repeated for a few sets. The set ends when your posture breaks or the bar starts pulling you into a slump, not when your grip finally opens.
Both and more. The traps and upper back work isometrically under heavy load the whole carry, the core braces continuously, and the grip gets the most obvious stimulus of all. It is one of the highest-return exercises per minute in the gym.
