Comment on CrossTalk 43: Exercise training intensity is/is not more important than volume to promote increases in human skeletal muscle mitochondrial content.doi:10.1152/physiol.00038.2018 Each side of this CrossTalk debate (Bishop et al. 2019; MacInnis et al. 2019) have properly defended their views. Another way to shed light on the importance of trainingintensityorvolumemaycomefrom studies on exercise in hypoxia through the interdependence of environmental oxygen availability and mitochondrial oxidative phosphorylation.