The "coup to take" is quite simple, just do not go too fast and the movement comes naturally. more you accelerate, the more it becomes heavy and tiring.
You will surpis muscle work in minutes.
Only downside is super fragile. At the slightest fall, you distort the mechanisms and start to feel the jolts that make the high-speed device unusable (pain ...)
Concerning the different models is gadget. The neon only serves to look pretty, as to counter the aim of this unit is to operate a few minutes on each arm and each way, not to make a speed record.
So my advice for your talks, take the basic model, if it is to offer, feel free to
