Figure 2. Illustration of lactate shuttling during exercise (the cell‐cell lactate shuttle).

Lactate released from muscles, skin and other driver cells provides energy for working muscles (Stanley et al. 1986; Bergman et al. 1999 b), heart (Gertz et al. 1981, 1988; Bergman et al. 2009 b) and brain (Glenn et al. 2015 a). Moreover, lactate released from working muscles (Stanley et al. 1986; Bergman et al. 1999 b) and other driver cells such as adipose tissue is the major gluconeogenic precursor (Stanley et al. 1988; Bergman et al. 2000) and brain fuel, even after injury when lactate supplementation may be efficacious (Brooks & Martin, 2014). Revised from Brooks (2018).