Well, if you're sitting up straight you don't have to use your core muscles, since all you have to do is balance your butt on the seat.
When you lean forward and use the bar, you have to engage your abs to maintain a neutral spine (unlike the chickie on the bike at the top frame of the forum - her spine ain't neutral and it's driving me NUTS!!!)
Just a pet peeve of mine.... Be Kind To Your Spine!!!
Last edited by KnottedYet; 02-02-2007 at 06:31 AM.
"If Americans want to live the American Dream, they should go to Denmark." - Richard Wilkinson