I may be looking at it with my professional physiotherapists eye, but it seems like he's having to support / stiffen his upper body much more, almost as if the handlebars are acting as a constriction. His movement is much more lower body intensive without seemingly as much propulsion.
Whilst I agree that using your upper body isn't what bike riding is about, it seems like the 16" limits any kind of motion, which in turn causes a contraction / more effort to "be there". There may also (most likely) be an issue of the seat postion (pelvis relative to legs relative to arms) or seat size? Issues especially for taller people riding long distances?
IOW - he doesn't look to be 'sitting neutral' compared to the bigger bike. Watch it in motion and tell me what you think? Something is clearly different...
BTW - never ridden one, so can't comment if that that actually what happens IRL.
Last edited by kbits; 01-10-08 at 09:51 AM.