You don't have to be a farmer for this one, or even know the words to Old McDonald. Grab yourself a heavy object and get walking. As simple as that. The heavier the load, the shorter the distance, and vice versa.
Will work your core and grip like nothing else, and depending on the carry position will nail your traps, shoulders, back and legs too.
The Results Room track is the perfect spot for these. You can go up and down as many lengths as you need. Just remember to lift and put down your weights with a strong neutral spine, and to keep your spine tall and core tight while carrying. Your body will naturally want to be in a good carry position to make this as efficient as possible.