Fig. 2. The effect of a cycle of normoxia, anoxia and re-oxgenation on heat output and interstitial lactate and K⁺ concentrations (means ± s.e.m.) in frog sartorius muscle at 20°C. Interstitial lactate and K⁺ levels were determined from microdialysis effluents of muscle interstitial space during continuous micro-calorimetric monitoring of heat flux. The lack of change in interstitial [K⁺] suggests that anoxia and re-oxygenation did not increase K⁺ loss from skeletal muscle. (From West and Boutilier, 1998.)