McCleave, EL, Ferguson-Stegall, L, Ding, Z, Doerner, PG III, Wang, B, Kammer, LM, and Ivy, JL. A low carbohydrate-protein supplement improves endurance performance in female athletes. J Strength Cond Res 25(4): 879-888, 2011-The purpose of this study was to investigate if a low mixed carbohydrate (CHO) plus moderate protein (PRO) supplement, provided during endurance exercise, would improve time to exhaustion (TTE) in comparison to a traditional 6% CHO supplement. Fourteen (n = 14) trained female cyclists and triathletes cycled on 2 separate occasions for 3 hours at intensities varying between 45 and 70% V̇O2max, followed by a ride to exhaustion at an intensity approximating the individual's ventilatory threshold average 75.06% V̇O2max. Supplements (275 mL) were provided every 20 minutes during exercise and were composed of a CHO mixture (1% each of dextrose, fructose, and maltodextrin) + 1.2% PRO (CHO + PRO) or 6% dextrose only (CHO). The TTE was significantly greater with CHO + PRO in comparison to with CHO (49.94 ± 7.01 vs. 42.36 ± 6.21 minutes, respectively, p < 0.05). Blood glucose was significantly lower during the CHO + PRO trial (4.07 ± 0.12 mmol·L−1) compared to during the CHO trial (4.47 ± 0.12 mmol·L−1), with treatment × time interactions occurring from 118 minutes of exercise until exhaustion (p < 0.05). Results from the present study suggest that the addition of a moderate amount of PRO to a low mixed CHO supplement improves endurance performance in women above that of a traditional 6% CHO supplement. Improvement in performance occurred despite CHO + PRO containing a lower CHO and caloric content. It is likely that the greater performance seen with CHO + PRO was a result of the CHO-PRO combination and the use of a mixture of CHO sources.
Exercise Physiology and Metabolism Laboratory, Department of Kinesiology and Health Education, The University of Texas at Austin, Austin, Texas
Address correspondence to Dr. John L. Ivy, email@example.com.