Resistance bands strengths

Question

Not sure if this would actually be the correct place to ask this (perhaps math or physics?).

Say I have some resistance bands (to help doing pull ups).

Green band is marked as being able to assist with 50-100 lbs Purple band is marked as being able to assist with 30-70 lbs

If you were to overlay or “combine” these two bands and use them as one, would it be fair to assume that the strength assistance is just “adding” the two together to get an assist of 80-170 lbs? Or how does that math work, perhaps way more complicated than that?

Answer 1

Yes, you can simply add the resistances of bands when you overlay them, which is using them in parallel. Things get a little more complicated when you combine them in series, i.e. joined end-to-end.

https://en.wikipedia.org/wiki/Series_and_parallel_springs

Also, the actual meanings of the nominal band resistances will vary from manufacturer to manufacturer, however, as you don't know at what amounts of stretch those 50 and 100lbs resistances were measured. But it's quite safe to assume that if you overlay a 50-100lbs band and a 30-70lbs band from the same manufacturer, the result will be equivalent to an 80-170lbs band.