To examine the role of both endurance exercise and nutrient supplementation on the activation of mRNA translation signaling pathways post-exercise, rats were subjected to a three-hour swimming protocol. Immediately following exercise, the rats were provided with a solution containing either 23.7%w/v carbohydrates (CHO), 7.9%w/v protein (PRO), 31.6%w/v (23.7%w/v CHO + 7.9%w/v PRO) carbohydrates and protein (CP), or a placebo (EX). The rats were then sacrificed at 0, 30, and 90 minutes post-exercise, and phosphorylation states of mammalian target of rapamycin (mTOR), ribosomal S6 kinase (p70^S6K), ribosomal protein S6 (rpS6), and 4E-binding protein 1 (4E-BP1), were analyzed by immunoblot analysis in the red (RQ) and white (WQ) quadriceps muscle. Results demonstrated that rat groups provided with any of the three nutritional supplements (CHO, PRO, CP) transiently increased the phosphorylation states of mTOR, 4E-BP1, rpS6, and p70^S6K compared to EX rats. Although CHO, PRO, and CP supplements phosphorylated mTOR and p70^S6K after exercise, only CP elevated the phosphorylation of rpS6 above all other supplements 30 min post-exercise and 4E-BP1 30 and 90 min post-exercise. Furthermore, the phosphorylation states of 4E-BP1 (r²=0.7942) and rpS6 (r²=0.760) were highly correlated to insulin concentrations in each group. These results suggest that CP supplementation may be most effective in activating the mTOR-dependent signaling pathway in the postprandial state post exercise, and that there is a strong relationship between the insulin concentration and the activation of enzymes critical for mRNA translation.