Training can improve insulin sensitivity in individuals with type 2 diabetes (Dela et al., 1995; Holten et al., 2004; Krotkiewski et al., 1985), but some patients who engage in exercise may fail to achieve the anticipated improvements in glycaemic control (Bouchard et al., 2012; Stephens & Sparks, 2015). This evidence concerns the gene INS and type 2 diabetes mellitus.