Contraindicated with Mad Dogg (Johnny G) is any sort of stretching ON the bike -- some methods teach for example a hip flexor stretch by sitting in the saddle and putting your leg up on the bars. Other contraindicated moves are push-ups on the bike -- some teach standing out ot the saddle and doing push-ups on the bars or figure 8s with your upper body while pedaling. Or there is the sort of "squat" while you are out of the saddle -- talk about a horrific thing to do to one's knees. Johnny G supports none of these moves.

I think with jumps it depends on how you do them and preserving the integrity of your form. Same with running on the bike. If you are bouncing wildly, your have lost form...your form should resemble as closely as possible to when you are on the road. I really watch my students closely when we do jumps or running because those are the most common times they start to lose form.

Actually Fredrick, spinning most closely resembles road riding in form, etc. than mountain biking I think, but certainly the cardio piece transcends both. And if you goal is to really get better on your road bike, you would be most advantaged to train on an indoor trainer with your bike. BUT that is usually toooo boring!!!! So alas, that's why spinning is such a hit!