Carbohydrate Effects on Post-Exercise Performance in Prepubescent Girls

Abstract

Carbohydrate (CHO) consumption is a common practice during variable-intensity exercise (VIE) such as team sports. The effects of CHO on performance during VIE have been studied in adults; however, the effects are less defined in children and apparently not at all in prepubescent girls. PURPOSE: To investigate the effects of a 6% CHO drink on a one-minute performance test following 30-minutes of VIE in prepubescent girls. METHODS: Ten girls (10.4±0.7 yrs.) participated in this study. During the initial visit, maximal aerobic power was determined followed by a familiarization of the protocol used during the next two visits in which the child consumed either a CHO drink or an electrolyte-matched placebo (PL). The experimental protocol involved two 15-minute bouts of VIE (20, 55, 95% maximal aerobic power and 6-second maximal sprint); beverages were consumed prior to exercise and after each 15-minute segment. A one-minute performance trial was then completed at maximal effort. Measurements during VIE included heart rate (HR), rating of perceived exertion (RPE), sprint mean power (MP) and sprint peak power (PP). During the one-minute performance bout, HR, RPE, PP, total work (TW), and fatigue index (FI) were assessed. Data were analyzed using a 2-way ANOVA and paired t-tests. RESULTS: VO2max was 39.7±5.5 mL∙kg-1∙min-1 and HRmax was 196±11 bpm. During VIE, there were no interaction effects, no trial effects (p>0.05) for HR, %HRmax, RPE, sprint MP, sprint PP and no time effects (p>0.05) for HR, %HRmax, or MP. However, there were time effects (p<0.05) for RPE (VIE1<VIE2) and PP (VIE1>VIE2). No differences were found between trials (CHO vs. PL) for one-minute performance for HR (190±9 vs. 189±9 bpm), %HRmax (97.0±3.2 vs. 96.6±3.0 %), RPE (7.8±2.3 vs. 8.1±1.9), PP (238±70 vs. 235±60 W), FI (54.7±10.0 vs. 55.9±12.8 %), and TW (9.37±2.6 vs. 9.37±2.1 kJ). CONCLUSION: A 6% CHO drink is ineffective at improving one-minute performance following 30-minutes of VIE in pre-pubertal girls. Based upon the current findings, CHO supplementation does not appear to be beneficial with respect to improving performance for prepubescent children completing VIE activity lasting 30-minutes.