Originally Posted by
urbanknight
Incorrect. You still have to expend the energy to move yourself as well as the bag. If you take the bag away altogether, the second guy is still moving 40 more lb than the first.
An oversimplification perhaps, but I intentionally neglected the
dynamic mass of the rider since the rider's skill and ability to conserve momentum plays a much more significant part in mtb than in your asphalt reality. Certainly you'd agree that in either discipline dropping 1 lb of body weight is less beneficial to performance than 1 lb of bike weight.