Certified professional ergonomist Blake McGowan summarizes the comprehensive review of literature on the maximum acceptable forces of pushing and pulling carts in this installment of The Bottom Line. Check it out.
Garg A, Waters T, Kapellusch J, Karwowski W. (2014). Psychophysical basis for maximum pushing and pulling forces: A review and recommendations. Int J Ind Ergon. Mar;44(2):281-291.
Read the full study for the regression equations.