J. N. Kubes, A. Hall, K. Belton-Sharp, N. Nelson, W. M. Silvers

Whitworth University, Spokane, WA

Much research has demonstrated that the use of carbohydrate (CHO) supplements can improve endurance exercise performance. Some supplement manufacturers recommend CHO dosages smaller than those shown to elicit an ergogenic effect. In addition, some manufacturers suggest ingestion of their products 15 min prior to exercise, though more research has demonstrated CHO supplement ingestion 30 min prior to exercise enhances endurance performance. PURPOSE: The purpose of this study was to investigate the effects of manufacturer-suggested dosages of CHO ingestion 15 and 30 min pre-exercise on subsequent short-duration endurance performance. METHODS: Fourteen healthy, college-aged, recreationally active males and females (nm = 2, nf = 12, height: 170 ± 10 cm, weight: 67.6 ± 10.1 kg; age: 18-22 yrs) completed a total of three sessions: one session without CHO supplementation (CON) and two sessions that implemented CHO supplementation 15 min (CHO15) and 30 min (CHO30) prior to exercise, respectively. A repeated measures analysis of variance was utilized to determine significant differences between experimental conditions for the following dependent variables: 2 mile running time trial (TT), heart rate (HR), and respiratory exchange ratio (RER). RESULTS: There was no significant difference in TT (CON: 18.56 ± 3.25 min, CHO15: 18.39 ± 3.31 min, CHO30: 18.31 ± 3.28 min; p = 0.758) between the three ingestion conditions. Similarly, there were no significant differences in HR (CON: 180.5 ± 10.7 bpm, CHO15: 174.8 ± 12.4 bpm, CHO30: 175.7 ± 15.7 bpm; p = 0.336) and RER (CON: 0.91 ± 0.02, CHO15: 0.92 ± 0.02, CHO30: 0.92 ± 0.03; p = 0.259) between the three conditions. CONCLUSIONS: Under these research conditions, CHO ingestion 30 min prior to exercise did not improve TT performance. The primary explanations for the observed results were attributed to the short-duration TT and the standardized CHO dosage used. It is probable that the TT was not long enough to observe the notable effects of CHO supplementation. Also, the amount of CHO dosage was not scaled for body weight in-line with previous research. Rather, the dosage was based upon manufacturer recommendations, which was probably too low to observe an ergogenic effect. Future research is needed to investigate the ergogenic effects of CHO ingestion based on manufacturer recommendations in other time conditions and performance situations.

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