Coinciding exercise with peak serum caffeine does not improve cycling performance.
OBJECTIVE
To investigate whether coinciding peak serum caffeine concentration with the onset of exercise enhances subsequent endurance performance.


METHODS
Randomised, double-blind, crossover.


METHODS
In this randomised, placebo-controlled, double-blind crossover study, 14 male trained cyclists and triathletes (age 31±5year, body mass 75.4±5.7 kg, VO₂max 69.5±6.1 mL kg⁻¹ min⁻¹ and peak power output 417±35W, mean±SD) consumed 6 mg kg(-1) caffeine or a placebo either 1h (C(1h)) prior to completing a 40 km time trial or when the start of exercise coincided with individual peak serum caffeine concentrations (C(peak)). C(peak) was determined from a separate 'caffeine profiling' session that involved monitoring caffeine concentrations in the blood every 30 min over a 4h period.


RESULTS
Following caffeine ingestion, peak serum caffeine occurred 120 min in 12 participants and 150 min in 2 participants. Time to complete the 40 km time trial was significantly faster (2.0%; p=0.002) in C(1h) compared to placebo. No statistically significant improvement in performance was noted in the C(peak) trial versus placebo (1.1%; p=0.240). Whilst no differences in metabolic markers were found between C(peak) and placebo conditions, plasma concentrations of glucose (p=0.005), norepinephrine and epinephrine (p≤0.002) were higher in the C(1h) trial 6 min post-exercise versus placebo.


CONCLUSIONS
In contrast to coinciding peak serum caffeine concentration with exercise onset, caffeine consumed 60 min prior to exercise resulted in significant improvements in 40 km time trial performance. The ergogenic effect of caffeine was not found to be related to peak caffeine concentration in the blood at the onset of endurance exercise.
The University of Queensland, School of Human Movement Studies, Australia. tskinner@hms.uq.edu.au
Tina L
TL
Skinner
David G
DG
Jenkins
Dennis R
DR
Taaffe
Michael D
MD
Leveritt
Jeff S
JS
Coombes
D000328:Adult; D054874:Athletic Performance / Q000502:physiology*; D001642:Bicycling / Q000502:physiology*; D001786:Blood Glucose / Q000378:metabolism; D002110:Caffeine / Q000097:blood*; D000697:Central Nervous System Stimulants / Q000097:blood*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004837:Epinephrine / Q000097:blood; D006801:Humans; D008297:Male; D009638:Norepinephrine / Q000097:blood; D058573:Performance-Enhancing Substances / Q000097:blood; D010807:Physical Endurance; D013997:Time Factors
D001786:Blood Glucose; D000697:Central Nervous System Stimulants; D058573:Performance-Enhancing Substances; D002110:Caffeine; D009638:Norepinephrine; D004837:Epinephrine