A bout of prolonged aerobic exercise can enhance the sensitivity of muscle glucose uptake to insulin, and this may be mediated by activation of 5′-adenosine monophosphate-activated protein kinase (AMPK). The aim of this study was to examine whether high-intensity short-term exercise resulting in a significantly greater increase in the activation of AMPK is more effective in enhancing muscle insulin sensitivity compared with low-intensity prolonged aerobic exercise. We measured insulin sensitivity after high-intensity intermittent swimming (HIS) or low-intensity continuous swimming (LIS) exercise in rat epitrochlearis muscle. During HIS, the rats underwent eight 20-second bouts of swimming with a weight equal to 18% of body weight. The LIS rats swam with no load for 3 hours. High-intensity intermittent swimming increased (P < .05) 2-deoxyglucose uptake ∼8-fold, whereas LIS increased it (P < .05) ∼2-fold immediately after exercise compared with rested muscle. This response was associated with an increase (P < .05) in phosphorylation of AMPK Thr¹⁷² and its downstream target acetyl-coenzyme A carboxylase (ACC) Ser⁷⁹ in HIS (13- and 6-fold, respectively) and LIS (2.8- and 2-fold, respectively) immediately after exercise. In contrast, submaximal (30 μU/mL) insulin-stimulated 2-deoxyglucose uptake measured 4 hours after exercise was 73% and 46% higher (P < .05) in LIS and HIS, respectively, compared with rest. The HIS exercise resulted in a greater activation of AMPK compared with LIS, but insulin sensitivity was higher after LIS compared with HIS. The results suggest that HIS is not more effective in enhancing insulin sensitivity than LIS. Thus, AMPK activation immediately after exercise may not be the only factor that determines the magnitude of the exercise-induced increase in insulin sensitivity in rat epitrochlearis muscle.