energy expended during exercise

["Beth Glace" <lb@nismat.org>]

I can't speak about the adequacy of the current mimimum weight 
standards, but I must disagree with Joe regarding energy expended 
when moving:
"Sorry, Bob, but your physics is off.  Energy is only expended moving 
a mass against resistance (such as gravity).  It takes more energy to
*lift* a given weight a given height, but not to move it horizontally.
All else being equal it takes no more energy to move 200 pounds one
*level* mile than to move 100 pounds one level mile."

Energy expended when walking or running is highly dependent upon body 
weight.  Although weight is not being lifted vertically  it is 
being propelled, overcoming inertia and the force of gravity.  
Measurements of movement economy [the energy cost of moving at a 
certain pace] must always therefore be expressed per Kilogram or per 
pound.  Below I give example energy expenditures for humans of 
various body weights at a walk [4 miles/hr]  and at a run [10 mph].
       100 lb person at 4 mph expends 4.1 kcals per minute
       200 lb person at 4 mph expends 7.0 kcals per minute
       100 lb person at 10 mph expends 11.4 kcals per minute
       200 lb person at 10 mph expends 22.0 kcals per minute
[*McCardle, Katch and Katch]
As you can see, energy expenditure roughly doubles as body weight 
doubles.  It isn't surprising then that most endurance athletes are 
not heavy weights.

Beth Glace, MS
Sports Nutritionist