Effect of carbohydrate consumption on the plasma FFA and human growth hormone ( hGH ) concentrations during prolonged exercise

Journal of Exercise Nutrition & Biochemistry 1999;3(2):25-36.

Abstract

The purpose of the present study was to determine whether carbohydrate consumption in untrained subjects could maintain a plasma glucose concentration during 1-h cycling exercise. In addition, it would be investigated whether this CHO supplementation could affect the plasma FFA and hGH levels. The six college male students volunteered for this study (age, 24.2±3.42 years; weight, 77.1±129 ㎏; height, 179.4±4.92 ㎝; VO_2max, 39.82±9.74 ㎖/㎏/min). The exercise regimen consisted of cycling for 60 min at 60% of VO_2max. Each subjects completed two randomly assigned treatments which were a water consumption(CON) and 6% carbohydrate solution(CHO). Each subject consumed 500 ㎖ CON or CHO 15 min prior to exercise. Either 150 ㎖ CON or CHO was consumed at 0, 15, 30, 45 and 60 min of exercise. Plasma was analyzed for glucose, lactate, FFA, insulin, and hGH concentrations. The rates of carbohydrate and fat oxidation were determined from the expired gas analysis. The plasma glucose levels in CON were significantly decreased during exercise but, in CHO, were maintained during exercise. FFA levels were significantly increased during exercise, but this increments were significantly attenuated by carbohydrate consumption. During exercise, hGH in CON was significantly greater than that in CHO. Thus, CHO, donsumption significantly affected the release of hGH during exercise. Therefore, we concluded that, at moderate intensity exercise, the maintenance of plasma glucose level during exercise significantly prevented the increase to the plasma FFA level ahd hGH concentration.