they would be using their back to pull against that 40-lb resistance...which is not that big a deal if you're in shape.
40 lb resistance is not a lot of weight but putting all that pressure onto a coin-sized ring that could only be pulled with one gloved finger? That seems really odd to me.
Think of the last time you carried groceries nowhere near 40 lb and the bags cut into your hand, even though you were using all four fingers. Increase the weight to 40lb, then quadruple it by putting it on one finger. That's a lot of force required.