Asp, Sven, Allan Watkinson, Nicholas D. Oakes, and Edward W. Kraegen. Prior eccentric contractions impair maximal insulin action on muscle glucose uptake in the conscious rat. J. Appl. Physiol. 82(4): 1327-1332, 1997.Our aim was to examine the effect of prior eccentric contractions on insulin action locally in muscle in the intact conscious rat. Anesthetized rats performed one-leg eccentric contractions through the use of calf muscle electrical stimulation followed by stretch of the active muscles. Two days later, basal and euglycemic clamp studies were conducted with the rats in the awake fasted state. Muscle glucose metabolism was estimated from 2-[¹⁴C(U)]deoxy-D-glucose and D-[3-³H] glucose administration, and comparisons were made between the eccentrically stimulated and nonstimulated (control) calf muscles. At midphysiological insulin levels, effects of prior eccentric exercise on muscle glucose uptake were not statistically significant. Maximal insulin stimulation revealed reduced incremental glucose uptake above basal (P < 0.05 in the red gastrocnemius; P < 0.1 in the white gastrocnemius and soleus) and impaired net glycogen synthesis in all eccentrically stimulated muscles (P < 0.05). We conclude that prior eccentric contractions impair maximal insulin action (responsiveness) on local muscle glucose uptake and glycogen synthesis in the conscious rat.