Jin Huang

Background: While caffeine may lower ratings of perceived exertion (RPE) or increase power output at a given RPE, whether caffeinated gum produces these effects during perceptually regulated exercise remains unclear. Aim: This study examined whether caffeinated gum increases self-selected cycling output at regulated-RPE in well-trained male athletes. Methods: Twelve well-trained male athletes (age: 21 ± 2 years; body mass: 77.3 ± 6.0 kg; VO_2peak: 47 ± 4 mL/kg/min) completed randomized, double-blind, placebo-controlled crossover trials separated by 7 days. Athletes chewed caffeinated gum (6 mg/kg) or placebo for 15 min before two 10 min cycling stages at RPE 4 and 7 (0–10 OMNI Scale). Cadence, power output, oxygen uptake, heart rate, and blood lactate concentration were measured. Results: Caffeinated gum significantly increased cadence (RPE 4: 72 ± 7 vs. 66 ± 10 rpm, p = 0.02; RPE 7: 77 ± 9 vs. 71 ± 11 rpm, p = 0.04), total work (53 ± 10 vs. 48 ± 10 kJ, p < 0.01; 87 ± 12 vs. 77 ± 14 kJ, p < 0.01), mean power output (88 ± 16 vs. 79 ± 16 W, p < 0.01; 146 ± 20 vs. 129 ± 24 W, p < 0.01) and peak power output (97 ± 18 vs. 88 ± 17 W, p < 0.01; 166 ± 27 vs. 147 ± 29 W, p = 0.01). Oxygen uptake was also higher in the caffeine condition at both RPE 4 (1.58 ± 0.12 vs. 1.42 ± 0.16 L/min, p = 0.005) and RPE 7 (2.17 ± 0.25 vs. 2.01 ± 0.22 L/min, p = 0.045), whereas heart rate and blood lactate concentration did not differ significantly between conditions (p > 0.05). Conclusion: Caffeinated gum (6 mg/kg) enhances self-selected cycling work at prescribed RPEs, indicating that it alters perceptually regulated exercise intensity in well-trained males.

Background/Objectives: Caffeine is a well-established ergogenic aid for endurance performance. However, the optimal intake strategy, specifically the administration method and dosage, remains uncertain. This systematic review and network meta-analysis compared the effectiveness of different caffeine administration methods and dosages on time-trial performance. Methods: A systematic review and network meta-analysis were conducted following PRISMA guidelines. A systematic search of PubMed, Embase, Web of Science, Scopus, and SPORTDiscus was conducted up to July 2025. Eligible studies were independently screened and quality-assessed by two reviewers. Pairwise and network meta-analyses were conducted to examine the effects of caffeine administration methods (e.g., capsules/tablets, gum, mouth rinse) and dosages (low: ≤3 mg/kg; moderate: 4–6 mg/kg) on time-trial performance. Results: Forty-eight studies with 612 participants were included. Low-dose capsules most effectively reduced completion time (standardized mean differences [SMD] = −0.34; 95% confidence interval [CI] −0.62, −0.06), followed by moderate-dose capsules (SMD = −0.31; 95% CI: −0.45, −0.17) and moderate-dose gum (SMD = −0.30; 95% CI: −0.57, −0.02). Low-dose capsules also had the highest probability of improving mean power output (SMD = 0.38; 95% CI: 0.09, 0.67), with moderate-dose capsules ranking second (SMD = 0.30; 95% CI: 0.12, 0.48). Conclusions: This systematic review and network meta-analysis identified low-dose caffeine capsules (≈3 mg/kg) as the most effective strategy for improving time-trial performance, with moderate-dose capsules and gum serving as viable alternatives. While these findings provide robust, actionable evidence for practitioners, meaningful inter-individual variability persists. Accordingly, future studies should integrate deeper mechanistic profiling (e.g., genetics and body composition) to advance personalized, evidence-based caffeine supplementation for athletes.