This looks so innocent- an ab roller, right? HA! I held a plank for about 30 seconds, then pulled up into a pike a few times, then "walked" with it attached to my feet, adding a pushup each time I moved an arm for about 12 "steps". It's 5 days later, and I still hurt DEEP inside.
Darn- it worked last night! Their site search isn't working at all now. I'll have to try to fix it later today. If it does start to work, type "wheel" into the search box if a wheel thing doesn't come up automatically.