muscular thrust, throwing, swinging
http://www.youtube.com/watch?v=-oZmH03cmMw
i think this concept is very applicable to tennis, so players don't get tied up in stuff like yanking left, or hitting 3 balls in a row is obsolete, or the arm has to be entirely passive etc etc.
all 3 sources of power are legit.... major muscle thrust in tsonga's fh, or wawrinka's serve, all legit shots... not to mention lots of 'throwers' in both ATP and WTA who focus more on thru the ball than yanking left.
every player uses all 3 power sources, but there is a degree of difference, in which one is the dominant.