This is a presentation which I have delivered at a few events in different versions which deals with the potential macro level consequences of th collection of exercise data through digital self-tracking. I suggested that the large-scale observation and analysis of human behaviour may be reconfiguring exercise activity as labour. I draw on theories of "digital labour" to discuss the ways in which work is being transformed in contemporary advanced capitalism. Building on this analysis, it will be proposed that a thermodynamic model of the exploitation of potential energy underlies the interest that corporations have shown in self-tracking.