Purpose: Inconsistent results among studies examining the effects of caffeine on exercise performance are potentially due to interindividual variability in biological responses to caffeine ingestion. The aims, therefore, of the present study were to identify high and low caffeine responders and compare the influence of caffeine on exercise performance and biological responses between groups during a simulated soccer-game protocol on treadmill. Methods: Well-trained soccer players were distinguished as high (n = 11) and low (n = 9) caffeine responders based on resting blood pressure, plasma glycerol, nonesterified fatty acid, and epinephrine responses to caffeine. Participants underwent 2 simulated soccer-game protocols on a treadmill after caffeine (6 mg·kg−1) or placebo ingestion. Exercise performance and several biological responses were evaluated. Results: Exercise performance did not differ between the high and low responders to caffeine (P > .05). However, time to fatigue (high, caffeine: 797 [201] s vs placebo: 487 [258] s; low, caffeine: 625 [357] s vs placebo 447 [198] s) and countermovement jump (high, caffeine: 42.1 [5.5] cm vs placebo: 40.5 [5.7] cm; low, caffeine: 41.0 [3.8] cm vs placebo: 38.8 [4.6] cm) improved with caffeine relative to placebo (P < .001). Rating of perceived exertion was lower (P < .001) in high (13.4 [2.3]) than in low responders (14.3 [2.4]) with caffeine ingestion. Conclusions: Caffeine improved aerobic endurance and neuromuscular performance in well-trained soccer players regardless of their responsiveness to caffeine at rest. Since no changes in substrate utilization were found with caffeine supplementation, performance improvements could be attributed to positive effects on the central nervous system and/or neuromuscular function, although the precise mechanism remains unclear.

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Background Equivocal findings examining the influence of caffeine on performance and biological responses to exercise may be due to inter-individual variability in cardiorespiratory or neuromuscular fitness. This study examined whether the effects of caffeine ingestion on exercise performance and biological responses to prolonged intermittent exercise to exhaustion depend on cardiorespiratory or neuromuscular fitness. Methods Twenty male soccer players, separated according to either cardiorespiratory fitness (high vs medium) or neuromuscular fitness (high vs medium) underwent two trials simulating the cardiovascular demands of a soccer game to exhaustion on treadmill after ingesting either caffeine (6 mg∙kg− 1) or placebo. Physical performance, cardiorespiratory and metabolic parameters and blood metabolites were evaluated. Results Time to exhaustion (719 ± 288 vs 469 ± 228 s), jump height (42.7 ± 4.2 vs 38.6 ± 4.4 cm), heart rate (163 ± 12 vs 157 ± 13 b∙min− 1), mean arterial blood pressure (98 ± 8 vs 92 ± 10 mmHg), plasma glucose (5.6 ± 0.7 vs 5.3 ± 0.6 mmol∙l− 1) and lactate (3.3 ± 1.2 vs 2.9 ± 1.2 mmol∙l− 1) were higher, while rating of perceived exertion (12.6 ± 1.7 vs 13.3 ± 1.6) was lower with caffeine vs placebo (p < 0.01), independent of cardiorespiratory or neuromuscular fitness level. Reaction time; plasma glycerol, non-esterified fatty acids and epinephrine; carbohydrate and fat oxidation rates; and energy expenditure were not affected by caffeine (p > 0.05). Conclusions Caffeine was effective in improving endurance and neuromuscular performance in athletes with either high or medium cardiorespiratory and neuromuscular fitness. Cardiorespiratory and neuromuscular fitness do not appear to modulate the ergogenic effects of caffeine supplementation in well-trained athletes.

The purpose of the study was to investigate the effect of dry-land priming (DLP) versus swimming priming (SP) on the 50 m crawl performance of well-trained adolescent swimmers. Thirteen adolescent swimmers were randomly assigned to perform either a DLP or SP 24 h prior to a 50 m sprint crawl time-trial. Baseline measurements included a 50 m sprint crawl time-trial as a control (C) condition, the evaluation of body composition, countermovement jump (CMJ), isometric peak torque (IPT), and rate of torque development (RTD). Rating of perceived exertion (RPE) was obtained following the DLP and SP programs. Both DLP and SP significantly decreased the 50 m crawl time-trial, by −2.51 ± 2.43% and −2.59 ± 1.89% (p < 0.01), respectively, compared with the C time-trial. RPE was not different between DLP and SP (p = 0.919). CMJ performance remained unchanged after DLP and SP programs compared with the C trial (p > 0.05). The percentage decrease in the 50 m crawl after DLP was significantly correlated with the percentage decrease in the 50 m crawl following SP (r = 0.720, p = 0.006). CMJ power, lean body mass, IPT, and RTD were significantly correlated with 50 m crawl performance. These results suggest that both DLP and SP strategies, when applied 24 h prior to a 50 m crawl time-trial, may enhance performance in well-trained adolescent swimmers.