Caffeine, widely recognized as an ergogenic aid, has undergone extensive research, demonstrating its effectiveness to enhance endurance performance. However, there remains a significant gap in systematically evaluating its effects on time trial (TT) performance in cyclists. This meta-analysis aimed to determine the efficacy of caffeine ingestion to increase cycling TT performance in cyclists and to evaluate the optimal dosage range for maximum effect. A search of four databases was completed on 1 December 2023. The selected studies comprised crossover, placebo-controlled investigations into the effects of caffeine ingestion on cycling TT performance. Completion time (Time) and mean power output (MPO) were used as performance measures for TT. Meta-analyses were performed using a random-effects model to assess the standardized mean differences (SMD) in individual studies. Fifteen studies met the inclusion criteria for the meta-analyses. Subgroup analysis showed that moderate doses of caffeine intake (4-6 mg/kg) significantly improved cycling performance (SMD _Time = -0.55, 95% confidence interval (CI) = -0.84 ~ -0.26, p < 0.01, I² = 35%; SMD _MPO = 0.44, 95% CI = 0.09 ~ 0.79, p < 0.05, I² = 39%), while the effects of low doses (1-3 mg/kg) of caffeine were not significant (SMD _Time = -0.34, 95% CI = -0.84 ~ 0.17, p = 0.19, I² = 0%; SMD _MPO = 0.31, 95% CI = -0.02 ~ 0.65, p = 0.07, I² = 0%). A moderate dosage (4-6 mg/kg) of caffeine, identified as the optimal dose range, can significantly improve the time trial performance of cyclists, while a low dose (1-3 mg/kg) does not yield improvement. In addition, the improvements in completion time and mean power output resulting from a moderate dose of caffeine are essentially the same in cycling time trails.

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.

Background/Objectives: The ergogenic effects of caffeine in team sports, particularly volleyball, have received significant research attention. This study sought to examine the effects of caffeine on both volleyball-specific and general performance outcomes. Methods: This systematic review comprises 11 studies, each utilizing a blinded crossover experimental design. A meta-analysis was conducted using a random-effect model to determine the standardized mean difference (SMD), estimated by Hedges’ g, with a 95% confidence interval (CI). Results: Caffeine supplementation improved volleyball-specific outcomes, including attack and serve accuracy (SMD: 0.50; 95% CI: 0.11–0.90; p = 0.01). Regarding nonspecific outcomes, caffeine increased single-jump performance (SMD: 0.23; 95% CI: 0.02–0.44; p = 0.03), repeated-jump performance (SMD: 0.51; 95% CI: 0.05–0.96; p = 0.03), and handgrip strength (SMD: 0.23; 95% CI: 0.03–0.42; p = 0.02), while decreasing agility test completion time (SMD: −0.32; 95% CI: −0.60–0.03; p = 0.03). Furthermore, caffeine increased the frequency of positive game actions during simulated volleyball matches (SMD: 0.84; 95% CI: 0.26–1.43; p < 0.01). Conclusions: Caffeine supplementation enhances physical performance and volleyball-specific actions during competition, supporting its role as an effective ergogenic aid for volleyball players.

Background/Objectives: This study aims to investigate the effects of caffeinated chewing gum on maximal strength, muscular power, and neural drive to the prime movers during bench press and back squat in resistance-trained men. Methods: Sixteen resistance-trained males participated in a double-blind, randomized trial, chewing either caffeinated gum (4 mg/kg) or placebo gum on two separate occasions, seven days apart. After chewing for 5 min, participants performed a maximal strength test followed by muscular power assessments at 25%, 50%, 75%, and 90% of their one-repetition maximum (1RM), completing with 3, 2, 1, and 1 repetition (s), respectively, for bench press and back squat. Surface electromyography data were recorded for each repetition. Results: Caffeinated gum did not significantly improve one-repetition maximum (1RM) for bench press (p > 0.05), but increased mean frequency (MF) and median frequency (MDF) in anterior deltoid, pectoralis major, and biceps brachii (all p < 0.05) compared to placebo. For back squat, 1RM increased with caffeinated gum, along with higher MF and MDF in vastus medialis (all p < 0.05). Caffeinated gum also improved mean and peak velocities, and mean and peak power outputs at 25–75% 1RM during the bench press (all p < 0.05), along with elevated MDF in pectoralis major and biceps brachii (all p < 0.05). Similar improvements were seen in mean and peak velocities during the back squat at 25–90% 1RM (all p < 0.05), along with higher MF and MDF in vastus medialis and increased normalized root mean square activity in gluteus maximus (all p < 0.05). Conclusions: Caffeinated chewing gum (4 mg/kg) enhanced muscular power (25–75% 1RM) in the bench press and improved maximal strength and muscular power (25–90% 1RM) in the back squat by increasing muscle recruitment in resistance-trained men.

The creativity of fitness coaches is crucial for maintaining the competitiveness of fitness enterprises. This study aimed to explore the factors, mechanisms, and moderating effects influencing the creativity of fitness coaches (n = 732) in Chinese fitness businesses, using partial least squares structural equation modeling (PLS-SEM) analysis. The results indicate that curiosity and sport commitment have a positive impact on knowledge-sharing and flow experience. In addition, knowledge-sharing and flow experience positively influence creativity. Importantly, the curiosity and sport commitment of fitness coaches affect creativity through knowledge-sharing and flow experience. Finally, social media usage positively moderates the relationship between knowledge-sharing and creativity. The findings of this study provide meaningful information and decision-making references for professionals in the fitness industry and academic researchers. Future efforts should emphasize the protection of fitness coaches’ creative achievements, with policymakers encouraged to establish relevant legal frameworks to safeguard innovation within the industry.

Understanding the psychological mechanism underlying physical activity (PA) participation in individuals with physical disabilities is crucial. In the current study, a conceptual model derived from extant literature was utilized to examine how perceived barriers, attitude, subjective norm, and self-efficacy are associated with intention and action of PA for people with disabilities. We recruited 371 adults (male = 215; female = 154; unidentified = 1; M _age = 53.20 ± 11.52 yr) with various physical disabilities. Structural equation modeling indicated that subjective norm, attitude, personal efficacy, environmental efficacy, and intention were positively associated with health actions, whereas internal, interpersonal, and environmental barriers showed negative associations. Internal and interpersonal barriers showed associations with lower motivation through self-efficacy and subjective norm, while environmental barriers were associated with diminished volitional processes through environmental efficacy. PA participation among individuals with disabilities appears to be shaped by different types of barriers and social cognitive variables across various stages of behavioral engagement. Limitations, practical implications, and future directions are also discussed.