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Failure of Protein to Improve Time Trial Performance when Added to a Sports Drink


Medicine & Science in Sports & Exercise: August 2006 - Volume 38 - Issue 8 - p 1476-1483
doi: 10.1249/01.mss.0000228958.82968.0a
APPLIED SCIENCES: Physical Fitness and Performance

Introduction: Recent studies have reported that adding approximately 2% protein to a carbohydrate sports drink increased cycle endurance capacity compared with carbohydrate alone. Howver, the practical implications of these studies work are hampered by the following limitations: (a) the rate of carbohydrate ingestion was less than what is considered optimal for endurance performance, and (b) the performance test (exercise time to fatigue) did not mimic the way in which athletes typically compete (i.e., a race in which a fixed distance or set amount of work is performed as quickly as possible).

Purpose: We tested the hypothesis that adding 2% protein to a 6% carbohydrate drink (CHO-PRO) would improve 80-km cycling time trial performance, as compared with a 6% carbohydrate drink (CHO) and a nonenergetic sweetened placebo (PLAC).

Methods: Ten trained male cyclists (24 ± 2 yr; V̇O2peak = 63 ± 2 mL·kg−1·min−1; mean ± SE) performed an 80-km laboratory time trial (TT) on three occasions separated by 7 d. In a double-blind crossover manner, subjects ingested CHO-PRO, CHO, or PLAC at a rate of 250 mL every 15 min with no temporal, verbal, or physiological feedback.

Results: Time to complete the TT was 4.4% lower (P < 0.002) during CHO (135 ± 9 min) and CHO-PRO (135 ± 9) compared with PLAC (141 ± 10), with no difference between CHO and CHO-PRO (P = 0.92).

Conclusion: Ingesting 6% carbohydrate at a rate of 1 L·h−1 (60 g·h−1) improved an 80-km TT performance in trained male cyclists. However, adding 2% protein to a 6% carbohydrate drink provided no additional performance benefit during a task that closely simulated the manner in which athletes typically compete.

Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, Ontario, CANADA

Address for correspondence: Martin J. Gibala, Ph.D., Department of Kinesiology IWC AB122, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1; E-mail:

Submitted for publication November 2005.

Accepted for publication March 2006.

©2006The American College of Sports Medicine