Journal Title (Medline/Pubmed accepted abbreviation): J Strength Cond Res
Page numbers: 1225-1228
Summary of background and research design
Caffeine is widely consumed among non-athletes and athletes alike. Primary effects include a release of catecholamines and glucocorticoids into the central nervous system, which elevates circulation and blood pressure. Caffeine has been shown to increase running and cycling time to exhaustion, typically in endurance exercise modalities, however research on higher intensity, short duration exercise is equivocal. Caffeine appears to stimulate beta-endorphin release into the circulation, providing an analgesic (pain-diminishing) effect. The authors hypothesized that this caffeine-induced analgesic effect would enhance performance on an exhaustive upper-body task.
Ten healthy young college students (5 male, 5 female) were randomized to consume either placebo or caffeine gum in a crossover design (participant completes trials for both). The gum delivers 85% of the effective 100-mg dose within 5 minutes of chewing due to high vascularization of the mouth. Habitual caffeine use has no adaptive effect on analgesic response so participants were not screened for habitual caffeine use. Following 5 minutes of chewing caffeine gum or placebo, participants grasped a metal block attached to standard Olympic weight plates set to 30% of hand grip strength max (measured at baseline by hand grip dynamometer), with arm held to the side. Time to exhaustion was measured, and pain (Numeric Pain Rating Scale) and perceived exertion (Borg RPE) were verbally assessed at 15 second intervals until failure.
Summary of research findings
Time to exhaustion was numerically greater in caffeine group, but was not statistically significant, apparently due to large variance between participants. Participants had a significantly lower mean response on the pain scale with caffeine gum, although mean response on perceived exertion did not differ.
Interpretation of findings/Key practice applications
The caffeine gum provided an analgesic effect by reducing pain during the trial, although performance was not improved. It would have been of interest for the authors to depict inter-individual differences in time to exhaustion, as the high variance suggests that some participants responded to the caffeine more favorably than others. Perceived exertion was similar, therefore the primary effect of a small caffeine dose was reduced discomfort associated with fatigue while gripping an object. Such pain relief may be of use during strength and condition activities that require prolonged grasping of an object such as an Olympic weightlifting bar or kettlebell.