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

Date of Award

Spring 2010

Document Type


Degree Name

Master of Science (MS)


Department of Kinesiology


Nicholas D. Luden

Michael J. Saunders

Christopher Joseph Womack


Purpose: The purpose of this study was to determine the independent and combined effects of carbohydrate and caffeine ingestion on performance and physiological parameters during high-intensity aerobic cycling (~60 minutes). Methods: Ten cyclists (28 ± 3 yr, 73.2 ± 1.9 kg) performed 20 minutes of steady-state cycling (60% Wmax) followed by a simulated 20-km time trial (TT) under the following four treatment conditions: placebo (PLA), carbohydrate (CHO), caffeine (CAF), and a combination of CHO and CAF (CHO-CAF). One hour prior to exercise subjects ingested a placebo/caffeine capsule. Beverages (250 ml) were consumed immediately prior to the 20-min steady-state, immediately prior to the 20-km TT, and at the 20-min mark during the time trial. Subjects completed the treatment trials in a semi-randomized, double-blind, placebo fashion and trials were separated by ≥ 5 days. Results: CHO-CAF improved 20-km TT performance by 3.4% (93 sec) compared to PLA (p ≤ 0.05), whereas no differences were detected among CHO, CAF, and PLA. Similarly, CHO-CAF improved mean power output by 5% during the 20-km TT compared to the PLA trial. RER was elevated under all treatment conditions compared to PLA. Further, blood glucose was elevated in CHO-CAF compared to PLA post steady-state and post TT. Treatment conditions did not differentially impact VE, VO2, pre-exercise MVC, post-exercise MVC, RPE, and blood lactate. Conclusions: CAF and CHO improve 20-km time trial performance when taken together but not when taken independently. This appears to be possibly facilitated by peripheral (MVC) and metabolic modifications (RER + blood glucose). Regardless of the mechanism, these data suggest that cyclists should ingest CHO and CAF together to improve high-intensity time trial performance, while in the fed state.

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