I found this video by Extracycles which explains very eloquently what it means. And how if feels to ride one. For those who have a spare MTB lying around. This is the best option. For those who dont have MTB, u can get a Surly Dummy, which is built around the extracycle concept. Now, this will not win u any races, but if u are a parent who looking for more family time with ur wife and children... and ride together.. this might be worth considering. I will be getting one in about 4 weeks and will update once I put in some miles into it. Enjoy!