Abstract
Purpose: This study aimed to assess the requirement of protein in pre-exercise carbohydrate drinks for optimal endurance performance at high intensity and post-exercise fatigue recovery.Methods: Endurance performance at 85% peak of young men (age 20 ± 0.9 years, 2peak 49.3 ± 0.3 L/min) was measured for two consecutive days using cycling time to exhaustion and total work exerted 2 h after three isocaloric supplementations: RICE (50 g, protein: 1.8 g), n = 7; SOY + RICE (50 g, protein: 4.8 g), n = 7; and WHEY + RICE (50 g, protein: 9.2 g), n = 7.Results: Endurance performance was similar for the three supplemented conditions. Nevertheless, maximal cycling time and total exerted work from Day 1 to Day 2 were improved in the WHEY + RICE (+21%, p = 0.05) and SOY-RICE (+16%, p = 0.10) supplemented conditions, not the RICE supplemented condition. Increases in plasma interleukin-6 (IL-6) were observed 1 h after exercise regardless of supplemented conditions. Plasma creatine kinase remained unchanged after exercise for all three supplemented conditions. Increases in ferric reducing antioxidant power (FRAP) after exercise were small and similar for the three supplemented conditions.Conclusion: Adding protein into carbohydrate drinks provides no immediate benefit in endurance performance and antioxidant capacity yet enhances fatigue recovery for the next day. Soy-containing carbohydrate drink, despite 50% less protein content, shows similar fatigue recovery efficacy to the whey protein-containing carbohydrate drink. These results suggest the importance of dietary nitrogen sources in fatigue recovery after exercise.
Highlights
Protein is not the primary energy substrate supporting the highintensity exercise
The benefit of protein addition on endurance performance is abolished when antioxidants are included in the supplement (Romano-Ely et al, 2006), suggesting that free radicals originated from inflammation mediate the fatigue recovery
On Day 1, high-intensity endurance performance (Figure 2) indicated by time to exhaustion (Figure 3) 2 h following the pre-exercise beverage ingestion was similar for the rice alone (RICE), SOY + RICE, and WHEY + RICE supplemented conditions
Summary
Protein is not the primary energy substrate supporting the highintensity exercise. protein supplementation is known to accelerate healing during inflammation (Thomas, 1997). Nitrogen from protein and amino acids is essential for DNA synthesis and cell regeneration during recovery after intensive exercise (Yang et al, 2018; Tryfidou et al, 2020). The benefit of protein addition on endurance performance is abolished when antioxidants are included in the supplement (Romano-Ely et al, 2006), suggesting that free radicals originated from inflammation (phagocytosis) mediate the fatigue recovery. Soy supplementation does not seem to affect pro-inflammatory interleukin-6 (IL6) levels in randomized clinical trials (Beavers et al, 2009). It remains unknown whether adding natural soy into pre-exercise carbohydrate drinks can influence free radicals, endurance performance, and post-exercise fatigue recovery
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