# Q factor of [exercise] battle ropes vs. elastic tubing?

FloatingBones
Hello. I'm providing a technical review of a new exercise device: the "inertia wave". .
The inventor knows this device is fundamentally different from battle ropes. After playing with one for a few days, I agree. I think that the simplest way to explain this to civilians is through the system's Quality Factor.

I think these elastic tubes have a Q Factor of ~5 (depending on the tension of the lines). OTOH, battle ropes essentially have no stored energy and thus a very small Q Factor -- less than 1. In other words, the attractiveness of elastic tubing over battle ropes (or chains) is the amount of stored energy in the tubes themselves. The "inertia wave" tubes are alive: you move the tubes; the tubes move you. I like it. Jumping off the ground while the tubes are oscillating gives a trippy feeling.

Would it help to provide a video of the "inertia wave" tubes to help calculate their Q Factor? I can get them oscillating, and then just stop moving. Anything else I should capture? Thanks.

Mentor
A view from the side should make it easier to capture the amplitude. Attaching them to two fixed ends eliminates the human as damping or power source.

FloatingBones
Peak to trough for me is a bit more than 5 feet. After I get good, I may get it amped up to about 6 feet.
Attaching them to two fixed ends eliminates the human as damping or power source.

It's clear the human is simultaneously driving and damping. Upper back muscles get very warm in a short workout; that's characteristic of eccentric (i.e., energy-absorbing) muscle contractions. Things are most interesting when the line gets out of phase with your hands; I suppose I'll get better at keeping everything in phase.

About 2 years ago, I noticed that mechanical impedance could be used to model our structural network. That's the main reason this toy got my attention. I never studied mechanical impedance before, but I seem to have remembered most of the material from an EECS signal processing course in the 80s.

There's a very nice article in a Springer book "Computational Dynamics" (1995) that explores the application of an impedance model to our musculoskeletal network. I put an excerpt up here. Dr. Ito's use of "impedance matching" makes huge sense. There's also "Optimal workloop energetics of muscle-actuated systems: an impedance matching view." (2010; doi: 10.1371/journal.pcbi.1000795).