Using a wheelbarrow to carry loads of heavy earth, car parts, cinder blocks, and whatever else you can throw into it can be a big help when having to move this stuff from point A to point B. But a better way, and much easier on the muscles, back and joints, is a motorized wheelbarrow that can handle heavy loads while going up steep hills or over rugged terrain. Simply steer the wheelbarrow and let it do the heavy lifting on its own.
Motorized wheelbarrow pictured: Troy-Bilt Pack Horse 500-Pound Capacity 6 Cubic Foot 190cc Briggs & Stratton 650 Series Gas Powered Wheelbarrow
Of course these are far more expensive than regular wheelbarrows, put the price is justified considering how much it can speed up your work, and how it can save you from painful muscles.