Chronic ingestion of a low dose of caffeine induces tolerance to the performance benefits of caffeine
journal contributionposted on 16.12.2016 by Ross Beaumont, Philip Cordery, Mark P. Funnell, Stephen Mears, Lewis James, Phillip Watson
Any type of content formally published in an academic journal, usually following a peer-review process.
This study examined effects of 4 weeks of caffeine supplementation on endurance performance. Eighteen low-habitual caffeine consumers (<75 mg · day−1) were randomly assigned to ingest caffeine (1.5–3.0 mg · kg−1day−1; titrated) or placebo for 28 days. Groups were matched for age, body mass, V̇O2peak and Wmax (P > 0.05). Before supplementation, all participants completed one V̇O2peak test, one practice trial and 2 experimental trials (acute 3 mg · kg−1 caffeine [precaf] and placebo [testpla]). During the supplementation period a second V̇O2peak test was completed on day 21 before a final, acute 3 mg · kg−1 caffeine trial (postcaf) on day 29. Trials consisted of 60 min cycle exercise at 60% V̇O2peak followed by a 30 min performance task. All participants produced more external work during the precaf trial than testpla, with increases in the caffeine (383.3 ± 75 kJ vs. 344.9 ± 80.3 kJ; Cohen’s d effect size [ES] = 0.49; P = 0.001) and placebo (354.5 ± 55.2 kJ vs. 333.1 ± 56.4 kJ; ES = 0.38; P = 0.004) supplementation group, respectively. This performance benefit was no longer apparent after 4 weeks of caffeine supplementation (precaf: 383.3 ± 75.0 kJ vs. postcaf: 358.0 ± 89.8 kJ; ES = 0.31; P = 0.025), but was retained in the placebo group (precaf: 354.5 ± 55.2 kJ vs. postcaf: 351.8 ± 49.4 kJ; ES = 0.05; P > 0.05). Circulating caffeine, hormonal concentrations and substrate oxidation did not differ between groups (all P > 0.05). Chronic ingestion of a low dose of caffeine develops tolerance in low-caffeine consumers. Therefore, individuals with low-habitual intakes should refrain from chronic caffeine supplementation to maximise performance benefits from acute caffeine ingestion.
- Sport, Exercise and Health Sciences