All my exercise equipment is used, but low-mileage. Cleaning out a closet, I found a spring set...you know...handle on each end with coiled springs in-between, and you can put like up to five springs in-between the handles.
I left this unit around the house and started pushing/pulling on the unit. I cannot believe how much stronger I have gotten in just three weeks.
Then, again, maybe, I am not getting stronger, but my springs are getting weaker. Should have thought about that, before starting the post; now it's done:) Later.