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J Appl Physiol (May 31, 2002). doi:10.1152/japplphysiol.00249.2002
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Articles in PresS, published online ahead of print May 31, 2002
J Appl Physiol, 10.1152/jap.00249.2002
Submitted on March 25, 2002
Accepted on May 24, 2002

Effect of different protocols of caffeine intake on metabolism and endurance performance

Gregory R Cox1, Ben Desbrow1, Paul G Montgomery2, Megan Anderson1, Clinton R Bruce3, Theodore A Macrides4, David T Martin1, Angela Moquin1, Alan Roberts2, John A Hawley3, and Louise M Burke1*

1 Sports Science & Sports Medicine, Australian Institute of Sport, Canberra, ACT, Australia
2 Center for Sport Studies, University of Canberra, Canberra, ACT, Australia
3 Exercise Metabolism Group, RMIT University, Melbourne, Victoria, Australia
4 Medical Laboratory Science, RMIT University, Melbourne, Victoria, Australia

* To whom correspondence should be addressed. E-mail: louise.burke{at}ausport.gov.au.

We investigated the effect of different caffeine intake protocols on prolonged cycling in 2 separate studies using a similar experimental design, involving competitive athletes who undertook 4 x 2 h steady-state (SS) cycling bouts at 70% peak O2 uptake followed by a 7 kJ/kg time-trial (TT) under conditions of 'real-life' practice: 2 h post-meal [2 g/kg carbohydrate (CHO)] and with intake of a 6% CHO drink during exercise. In Study A, 12 subjects received, in a Latin square design, either 6 mg/kg caffeine ingested 1 h pre-exercise (PRECAF), 6 x 1 mg/kg caffeine every 20 min throughout SS (DURCAF), 2 x 5 mL/kg Coca ColaTM consumed between 100-120 min SS and during TT (COKE), or placebo (PLACEBO). Compared to PLACEBO, improvements in TT were: PRECAF: 3.4% [0.2% to 6.5%, 95% C.I.], DURCAF: 3.1% [-0.1 to 6.5%] and COKE: 3.1% [-0.2 to 6.2%]. Post-exercise urinary [caffeine] were <12 ug/ml for all subjects. In Study B, 8 subjects received 3 x 5 mL/kg of 4 identically flavoured cola drinks during the last 40 min of SS and during TT: decaffeinated, 6% CHO (CONTROL); caffeinated, 6% CHO (CAFFEINE); decaffeinated, 11% CHO (extraCHO) and caffeinated, 11% CHO (COKE). Compared to CONTROL, COKE enhanced TT by 3.3% [0.8-5.9%], with all trials showing a 2.2% TT enhancement (0.5-3.8% ; P<0.05) due to the caffeine content and a 1% enhancement (-0.7-2.7%) due to the additional CHO intake. We conclude 1) intake of 6 mg/kg caffeine enhanced performance of a TT undertaken after 120 min of SS, independent of timing of intake and 2) replacing sports drink with Coca ColaTM during the latter stages of exercise was equally effective in enhancing endurance performance, primarily due to intake of small amounts of caffeine (~1.5 mg/kg).




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