“…Indeed, when maximally recruited, as during exercise or an intense bout of shivering, muscle can account for up to 90% of whole-body oxygen uptake, an indirect measure of heat production (Stainsby & Lambert, 1979; Zurlo et al , 1990). During muscle contraction, heat is generated by the hydrolysis of ATP from three different ATPases: myosin ATPase (Stewart et al , 2010; Cooke, 2011; Little & Seebacher, 2013), which performs the contractile work, and SERCA (Block, 1994; Dumonteil, Barre & Meissner, 1995; Simonides et al , 2001; Morrissette, Franck & Block, 2003; de Meis, Arruda & Carvalho, 2005; Arruda et al , 2007; Kjelstrup et al , 2008; Bal et al , 2012; Inesi & Tadini-Buoninsegni, 2013; Little & Seebacher, 2013; Sahoo et al , 2013) and Na + /K + ATPase (Guernsey & Morishige, 1979; Muller & Seitz, 1984; Herpin, McBride & Bayley, 1987; Kelly & McBride, 1990; Rolfe & Brown, 1997; Karbowski, 2009), which reset resting ion gradients and membrane potential. To sustain these processes, ATP generation must be increased to match demand.…”