Effect of different protocols of caffeine intake on metabolism and endurance performance.
Competitive athletes completed two studies of 2-h steady-state (SS) cycling at 70% peak O(2) uptake followed by 7 kJ/kg time trial (TT) with carbohydrate (CHO) intake before (2 g/kg) and during (6% CHO drink) exercise. In Study A, 12 subjects received either 6 mg/kg caffeine 1 h preexercise (Precaf), 6 x 1 mg/kg caffeine every 20 min throughout SS (Durcaf), 2 x 5 ml/kg Coca-Cola between 100 and 120 min SS and during TT (Coke), or placebo. Improvements in TT were as follows: Precaf, 3.4% (0.2-6.5%, 95% confidence interval); Durcaf, 3.1% (-0.1-6.5%); and Coke, 3.1% (-0.2-6.2%). In Study B, eight subjects received 3 x 5 ml/kg of different cola drinks during the last 40 min of SS and TT: decaffeinated, 6% CHO (control); caffeinated, 6% CHO; decaffeinated, 11% CHO; and caffeinated, 11% CHO (Coke). Coke enhanced TT by 3.3% (0.8-5.9%), with all trials showing 2.2% TT enhancement (0.5-3.8%; P < 0.05) due to caffeine. Overall, 1) 6 mg/kg caffeine enhanced TT performance independent of timing of intake and 2) replacing sports drink with Coca-Cola during the latter stages of exercise was equally effective in enhancing endurance performance, primarily due to low intake of caffeine (approximately 1.5 mg/kg).
Cox
Gregory R
GR
Sports Science and Sports Medicine, Australian Institute of Sport, Belconnen, Australian Capital Territory 2616, Australia.
Desbrow
Ben
B
Montgomery
Paul G
PG
Anderson
Megan E
ME
Bruce
Clinton R
CR
Macrides
Theodore A
TA
Martin
David T
DT
Moquin
Angela
A
Roberts
Alan
A
Hawley
John A
JA
Burke
Louise M
LM
D000328:Adult; D001628:Beverages; D001642:Bicycling / Q000502:physiology; D001769:Blood / Q000378:metabolism; D002110:Caffeine / Q000008:administration & dosage* / Q000097:blood / Q000494:pharmacology / Q000652:urine; D050260:Carbohydrate Metabolism; D000697:Central Nervous System Stimulants / Q000008:administration & dosage* / Q000097:blood / Q000494:pharmacology / Q000652:urine; D004311:Double-Blind Method; D004326:Drinking; D006801:Humans; D008297:Male; D010807:Physical Endurance / Q000187:drug effects*; D005082:Physical Exertion; D011659:Pulmonary Gas Exchange / Q000187:drug effects; D012119:Respiration / Q000187:drug effects; D012649:Self Concept
D000697:Central Nervous System Stimulants; D002110:Caffeine