Low–dose caffeine administered in chewing gum does not enhance cycling to exhaustion
 
 
Journal Title (Medline/Pubmed accepted abbreviation):  J. Strength Cond. Res
Year: 2012
Volume: 26
Number: 3
Page numbers: 844-850

Summary of background and research design:

Background: Caffeine has been shown to increase performance, especially with moderate to high doses of about 3 or 4 to 13 mg/kg body weight (about 250-1000 mg/serving). However, it is unknown if a low dose of caffeine (200 mg or 2–3 mg/kg body weight) will have similar positive effects when administered in chewing gum form.

Hypothesis:Chewing gum that includes 200 mg caffeine per serving will increase cycling performance.

Subjects: 8 active males, age 26 ± 4 y. Some were moderate caffeine users.

Experimental Design: randomized, placebo–controlled, double–blinded, cross–over

Treatments: Caffeine administered as 2 pieces of Stay Alert chewing gum (200 mg total) either A) 35 min before cycling, B) during the warm–up (5 min before the trial), or C) 15 min into the start of the trial. One trial (trial D) there was no caffeine administered via the gum. It is estimated that, for the active treatment, 170 mg of caffeine was absorbed into the blood stream.
ST150– Fish oil supplementation for the 60 days before the strength training routine, then also during the 90 day strength training (150 days total)

Protocol:The participants were first familiarized with the stationary bike and assessed for VO2max. They then reported to the laboratory 4 times, one for each treatment, 1 week apart. They arrived in the morning (between 6:00–9:00am) after not eating for at least 4 hrs. Participants chewed gum 35 min before the trial, during the warm up, and 15 min after the start of the trial every session, the gum either containing caffeine or not, depending on the trial. The trial consisted of cycling at 85% of their maximum workload until they could not keep up the intensity (time to exhaustion). Blood samples were acquired 40 and 10 min before exercise and at completion. Blood was analyzed for hematocrit and concentrations of hemoglobin, free fatty acids, epinephrine, and norepinephrine. During exercise, respiratory gases were analyzed, heart rate was monitored, and blood glucose and lactate concentrations were assessed using finger prick blood samples.


Summary of research findings:
  • The time to exhaustion was about 33 ± 10 min for all trials, with no statistical differences between any trials.
  • There were no differences found between any trials for any of the biological parameters that were measured.
  • Norepinephrine, oxygen consumption, respiratory exchange ratio (RER), heart rate, lactic acid production, rating of perceived exertion, and leg pain escalated as the trial progressed, as expected, to reach a maximum around 20 min.
  • Blood glucose and serum free fatty acid concentrations did not change over the course of the study.

Key practice applications: About 170 mg of caffeine, as administered in chewing gum, did not improve performance on a time–to–exhaustion trial. This was unexpected, as other similar trials have shown positive effects. It is likely that caffeine–containing chewing gum may work for some, but not all, athletes (see limitations of this study).

Limitations

  • –  Most races are not time to exhaustion. It would have been interesting if the researchers instead assessed average speed and time it takes to complete a given distance.
  • –  Blood caffeine levels were not measured and, therefore, the amount of caffeine that was absorbed from the chewing gum matrix could only be estimated from previous studies.
  • –  The day–to–day caffeine usage of the participants was not accounted for. There are large individual differences in caffeine sensitivity and tolerance.
  • –  Because these trials were completed in the morning after not having eaten for at least 4 hrs, most of these participants had fasted overnight before the trial. This is not the typical state for exercise.
  • –  There was a large variability in trial times, and time to exhaustion protocols are known to have unreliable reproducibility.

 

Key search terms for this article (5-7 terms):caffeine, chewing gum, gum, cycling, endurance

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