The horsepower has to do with what you're pushing and whether it rolls or you have to lift things, but there are other value added things, like making you pay to get yourself to the job, not feeding you, and that you know where to put things. In the US there's also a lot of tax and job creation schemes that ensure corporations get the full value of the energy they use, but not for the worker to do so. Let's call it "an emerging science" ;)
If a corporation was a farm using horses, about 1/3 of the land is just feeding the horses. That's a very poor ratio of EROEI (energy returned on energy invested). Not knowing the value/price of the things you push around makes it difficult to determine your fit.
On level ground with a wheeled cart, the majority of your work is going to be just moving yourself around. They don't pay for that but it relates to the lifting and organizing functions.