HELP A POOR ORPHAN

[Thomas Paikeday]

I gave away most of my 35-year collection of dictionaries and related
reference works last year when I closed shop in Toronto, so I'd
appreciate some lexicographical help from anyone willing or able. I
would have turned to the online OED if I had it.

QUESTION: Is there a dictionary definition of MET or METS (display on
treadmills, as METS 3.5)?
I do have a few citations in the database of my current dictionary
(User's Webster, 2000) from HeartCorps, American Fitness, and EXERCISE,
but I am dying for a formal "published" dictionary definition. If I am
not mistaken, MET is from the acronym of "Maximum Energy Tolerance."

Is the following definition then acceptable? "A unit of energy
expenditure necessary to maintain various metabolic functions, one
MET/met being equal to the amount of work the heart performs when at
rest (resting metabolism)."

MORE POINTEDLY: When the display says METS 3.5, what exactly is it
telling you in plain English? Is it expenditure or tolerance? And why
the plural? Bad editing perhaps?