Way back (1992 ish) I worked as a chemical technician. Part of my responsibilities was to move large amounts of chemicals in boxes (4 gallons per box), and drums (55 gallon drums). Needless to say, I probably was in the best physical condition of my life during that 9 months or so.
But there was an upside. Since I worked off shift, I would need to drive the forklift to get my job done. So I went through the training (possibly the only person in history with a physics degree to be certified to drive a forklift), got certified, and moved a lot of product with that forklift.
I will admit, it was fun. One thing that if you are a normal person seems confusing, but for a physicist, it seemed logical was the fact that a forklift is least stable when it is not carrying anything. They tip over quite easily, and can be very hazardous to the operator and the folks nearby. However, as you approach the maximum load limit, the dynamics change, and it become the most stable it can be.
That meant when I was carrying a pallet of Freon dissolved in methanol (about 750# per 55 gallon drum), the machine was at its best performance.