Effect of Carbohydrate-Protein Supplementation on Endurance Training Adaptations: Post-exercise protein ingestion and endurance training

Purpose: To examine the influence of post-exercise protein feeding upon the adaptive response to endurance exercise training. Methods: In a randomised parallel group design, 25 healthy men and women completed 6 weeks of endurance exercise training by running on a treadmill for 30–60 min at 70–75% maximal oxygen uptake (VO _2max) 4 times/week. Participants ingested 1.6 g per kilogram of body mass (g kg BM ⁻¹) of carbohydrate (CHO) or an isocaloric carbohydrate–protein solution (CHO-P; 0.8 g carbohydrate kg BM ⁻¹ + 0.8 g protein kg BM ⁻¹) immediately and 1 h post-exercise. Expired gas, blood and muscle biopsy samples were taken at baseline and follow-up. Results: Exercise training improved VO _2max in both groups (p ≤ 0.001), but this increment was not different between groups either in absolute terms or relative to body mass (0.2 ± 0.2 L min ⁻¹ and 3.0 ± 2 mL kg ⁻¹ min ⁻¹, respectively). No change occurred in plasma albumin concentration from baseline to follow-up with CHO-P (4.18 ± 0.18 to 4.23 ± 0.17 g dL ⁻¹) or CHO (4.17 ± 0.17 to 4.12 ± 0.22 g dL ⁻¹; interaction: p > 0.05). Mechanistic target of rapamycin (mTOR) gene expression was up-regulated in CHO-P (+ 46%; p = 0.025) relative to CHO (+ 4%) following exercise training. Conclusion: Post-exercise protein supplementation up-regulated the expression of mTOR in skeletal muscle over 6 weeks of endurance exercise training. However, the magnitude of improvement in VO _2max was similar between groups.