A common problem with much fitness testing is that we tend to apply
mechanical definitions of work and power to the human body.
Work is defined as the counterforce moved a vertical distance. If we apply a force to the
counterforce and produce no movement, then the work is nil.
If the counterforce is 10 LBS and we move it vertically 10 inches, then the work performed
is 100 INCH LBS.
Power is the work performed per time.
Now apply this to the human body and suppose that a man holds a 100 LBS barbell in the
mid-range position of a barbell curl exercise. Suppose that he holds it perfectly
motionless. Since the barbell does not move; and according to the mechanical definition of
power which is founded on the more fundamental definition of work; the work and power
produced by the subject is zero. Therefore, by these definitions the subject is doing
nothing.
But why does the subject's face turn red? Why do his muscles weaken? Why do his pulse and
blood pressure and respiration increase? Why does his body begin to tremble? And why can't
he hold the barbell forever, since by our mechanical definitions of work and power he is
doing nothing?
Well, he is doing something. He is performing metabolic work, although he is holding the
barbell motionless and thereby defying the said mechanical definitions.
To take this further than what I heard from Arthur, pretend that we live in a fantasy
world where the metabolic chemistry can be removed from the body in such a way to
perfectly isolate and portray the metabolic work performed by the subject. Although we
accurately run the chemical reactions from beginning to end, we still have no way to
measure their work and power. We might measure the heat lost from the reactions and
quantify this as calories or BTU's, but very few energy combustions or conversions are
efficient with respect to the quantity of work performed. Even this fantasy is a hopeless
mess. If the science is imprecise, how can we expect a meaningful tool. Note that Cybex®
and other isokinetic companies have offered mechanical tests to assess metabolic power.