Strength is the first thing to increase for a few reasons, most of these having nothing to do with increasing actual strength, but rather your ability to access your strength. (davedreas.com)
In addition, these progressions can be measured only in terms of difficulty and not in terms of actual strength gained. (ashotofadrenaline.net)
In the studies done on a group of NCAA football players, the ZMA group showed 250 % more muscle strength gain than the placebo group, but in actual strength gains, the ZMA group showed 11.6 % compared to 4.6 % for the placebo group. (bodybuildingforyou.com)