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Mike Whittle
11-04-1994, 06:00 AM
Dear Biomch-l readers:

John Scholz's recent posting on strength distal to proximal (which I can't
answer) prompted me to ask a related question.

I have been teaching my students that muscle strength (in terms of force
production) depends on the cross sectional area, which increases with growth
as the square of linear dimensions. In contrast, weight increases as the
cube of linear dimensions, so people get relatively weaker as they get bigger.
This is the "party line", as I understand it. However, one of my students
pointed out that the lever arms presumably increase linearly with growth, so
that torque, being the product of force and distance, should increase in
proportion to body weight! I said I didn't know, and changed the subject!

Has anyone any opinions on this? The relative loss of strength is given as
a reason for children with walking problems to "go off their feet" (i.e. go
into a wheelchair) at around the age of 11 - but is this really true?

Michael W. Whittle, M.D., Ph.D.
Cline Chair of Rehabilitation Technology
The University of Tennessee at Chattanooga