Carbohydrate Supplementation and Perceived Exertion during Prolonged Running

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UTTER, A. C., J. KANG, D. C. NIEMAN, C. L. DUMKE, S. R. MCANULTY, D. M. VINCI, and L. S. MCANULTY. Carbohydrate Supplementation and Perceived Exertion during Prolonged Running. Med. Sci. Sports Exerc., Vol. 36, No. 6, pp. 1036–1041, 2004.Purpose:The purpose of this study was to investigate the relationship between carbohydrate energy substrate and hormonal regulation on the perception of exertion during prolonged running.Methods:Sixteen experienced marathoners ran on treadmills for 3 h at ~70% V̇O2max on two occasions while receiving 1 L·h−1 carbohydrate (C) or placebo (P) beverages. Blood and vastus lateralis muscle biopsy samples were collected before and after exercise.Results:The pattern of change in ratings of perceived exertion (RPE) over time was significantly different between C and P ingestion (P < 0.01) with attenuated RPE responses found in the latter part of the 3 h run. The pattern of change in the respiratory exchange ratio and carbohydrate oxidation rates were significantly greater (P < 0.01) in the C than P condition. Change in muscle glycogen content did not differ between C and P (P = 0.246). C relative to P ingestion was associated with higher plasma levels of glucose, insulin, and lactate and lower levels plasma cortisol.Conclusions:These data indicate that a lower RPE was associated with a higher carbohydrate oxidation, plasma glucose, and insulin levels, and lower plasma cortisol during prolonged running after C supplementation as compared with P feeding despite no differences in muscle glycogen content. These findings support a physiological link between RPE and carbohydrate substrate availability as well as selected hormonal regulation during prolonged running.

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