Hello Paul Great idea to reach out to the international PT community for further insight/direction. The key to this, and similar situations in which one is attempting to ascertain 'effectiveness' from a review of the literature, is to pay particular attention to the methods ie. the parameters selected (pulse duration, amplitude, number of contractions etc, the application (electrode size, distance, location; treatment duration, treatment frequency, number of sessions). I suggest that you refer to the publication by my colleagues and I (https://www.ncbi.nlm.nih.gov/pubmed/29162949), for further understanding of these issues. It is important to recognize that a modality is not 'always effective' nor 'never effective' but rather that the combination of the 'right/appropriate modality' with the 'right/appropriate methods' be used. For example, if the pulse duration and frequency utilized is more specific to sensory nerve depolarization (e.g TENS at 60 microsec and 250 Hz) and the outcome measure used is related to muscle strength it is highly unlikely that there will be a change in muscle strength (typically requiring 350-400 microsec at approx 50 Hz). Take home message: don't just report the conclusions of the authors of the studies but instead critically evaluate the methods that were used in order to determine whether the selected outcome measures are likely to be sensitive, specific and appropriate for the desired effect e.g. pain management vs muscle strengthening. Hope this helps.