Fig. 7. Power-cycle frequency relationships (means ± s.e.m.) at 4°C for sartorius and external oblique muscles taken from (4°C) air-access control frogs, normoxic cold-submerged frogs (12–16 weeks in air equilibrated water) and hypoxic cold-submerged frogs (12–16 weeks in 60 mmHg O₂). A general linear model was used to test for changes in power with cycle frequency and treatment, considering power as the dependent variable and frequency and treatment as independent variables. Power was significantly affected by cycle frequency but there was no significant effect of treatment (Frequency F_6,40=7.208, P<0.001; Treatment F_2,40=1.381, P=0.265). (G. N. Askew and R. G. Boutilier, unpublished observations.)