Signal magnitude area I'm confused by the SMA. I'm reading a paper which states that "SMA is the square root of the summation of the filtered acceleration signal". So I understand that it's $sma = \sqrt{\sum{samples}}$

I check the referenced paper, which says that "SMA is calculated after dividing area under the acceleration curve with the time interval". So $sma = {1 \over T} \sum samples$, which is some kind of average, which looks like what is on this StackOverflow question.

And the Wikipedia article is so new I'm not sure it's reliable.

In the end, what is exactly SMA as I couldn't find a proper definition online?
I've found a proper definition thanks to the following article:
http://www.rehab.research.va.gov/jour/2013/509/jrrd-2012-12-0233.html

This is what I've edited Wikipedia with:
$$f_{sma}= {1 \over {T}} {\int_{0}^{T} |x(t)-a_x|+|y(t)-a_y|+|z(t)-a_z| dt}$$

(It wasn't because of text-search but images-search. Algorithms are sometimes surprising)