It all depends where you draw the line with Plyos and Isos, and the results you achieve plus what you are working to create. There are training techniques that encompass both at the same time, it depends how much of a shock you want, its all down to the old chestnut of Feel. Do you take a Hammer or a Ruler for effect. . Punching skipping can loosely be termed Plyos, Isos I feel where the line is drawn is open to debate, well for me it is. Its a name and discription given to a form of static ressistance, which Hinders sometimes what you are trying to achieve same as Plyos. Ive got things where theres a bit of Both in fact everything. People ask what do you class that as , my answer is exercise .