If an initial muscle contraction is brief and is followed by a period (30-120sec) of rest, a secondary contraction will almost always be greater. The following findings by Enoka relating to this mechanism, Post-Tetanic Potentiation (PTP), reflect this naturally occurring mechanism of contractibility. The duration of the initial contraction, the period of rest, and the contractile history of the muscle can all influence the degree of increased contractibility (Nogueira, 2013.) These findings create reason to be skeptical of perspectives, techniques, modalities and practices that rely soley on the result of “muscle testing” for evidence of their perspective. Currently, this mechanism makes it impossible to determine the influence of these modalities.