The arch exerciser is not very challenging so in order to make it harder I did something. When you receive it, I'll send you a video of how i do it to make it more challenging...it's hard to describe.
Get the blue archexerciser: https://www.amazon.com/Elgin-Archxerciser-Pro-Resistance-Blue/dp/B00ACMJV9C/ref=sr_1_8?ie=UTF8&qid=1472481256&sr=8-8&keywords=arch+exerciser