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This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Date of Award

Spring 2013

Document Type


Degree Name

Master of Science (MS)


Department of Kinesiology


Previous studies have reported that adding protein (PRO) to a carbohydrate (CHO) solution can enhance endurance performance. This ergogenic effect may be a function of additional calories from supplemental protein/amino acids, but this thesis has not been directly examined. Additionally, L-alanine (ALA) is readily oxidized when provided during exercise; the impact that this has on metabolism and prolonged endurance performance is unknown. The purpose of this investigation was to assess performance and various cardiovascular and metabolic outcomes during prolonged cycling, to independently gauge the efficacy of whey PRO hydrolysate and ALA supplementation. Eight trained male and female cyclists (age: 22.3±2.0 years, weight: 70.0±2.8 kg, VO2max: 59.4±1.7 ml•kg-1•min-1) performed 120 min of constant-load cycling (55% of peak power, 161.9±7.4 W) followed by a 30-km time trial (TT) under placebo (PLA), PRO, and ALA conditions. TT performance was not different between treatments (PLA: 57.6±1.6 min, ALA: 58.8±1.5 min, PRO: 58.8±1.8 min). VE, VO2, heart rate, rating of perceived exertion, blood glucose, blood lactate, and gastrointestinal distress were also similar across experimental conditions. Conversely, serum interleukin-6 (IL-6) levels following 120 min of cycling were elevated above rest with PLA (pre: 0.56±0.16, post: 3.14±0.84) and ALA (pre: 1.14±0.46, post: 2.62±0.71) (p<0.05), but not with PRO intake (pre: 0.81±0.25, post: 1.55±0.32). The ingestion of PRO or ALA alone does not appear to enhance performance during prolonged cycling. Thus the ergogenic effects of CHO+PRO co-ingestion reported by others are likely not the result of additional energy from protein per se.

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