(a) transducing human fibroblast progenitor cells or human adipose stem cell progenitor cells with a viral vector comprising polynucleotides encoding reprogramming markers Oct4, Sox2, Klf4 and cMyc on day 1, which markers are expressed in the cells;

(b) culturing a subpopulation of cells within the population of transduced human fibroblast progenitor cells or human adipose stem cell progenitor cells which comprises cells having at least 2-fold increased expression of endogenous estrogen related receptor alpha (ERRα) and an increased level of at least one analyte selected from peroxisome proliferator-activated receptor gamma co-activator 1 alpha (PGC-1α), peroxisome proliferator-activated receptor gamma co-activator 1 beta (PGC-1β), or isocitrate dehydrogenase 3 (IDH3) by at least day 3 to day 5 following step (a) when compared to non-transduced human fibroblast progenitor cells or non-transduced human adipose stem cell progenitor cells; wherein the cells further display an increased metabolic rate defined by an increase in one or both of extracellular acidification rate and oxygen consumption rate and enhanced glycolysis, relative to cells which do not express the reprogramming marker ERRα, and, optionally,

(c) isolating a cell from the cultured subpopulation of cells following step (b), thereby generating a human induced pluripotent stem cell progenitor or human induced pluripotent stem cell in vitro.