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.

Physical activity could improve the muscle fitness of youth, but the systematic analysis of physical activity elements and muscle fitness was limited. This systematic review and meta-analysis aim to explore the influence of physical activity elements on muscle fitness in children and adolescents. We analyzed literature in Embase, EBSCO, Web of Science, and PubMed databases from January 2000 to September 2020. Only randomized controlled studies with an active control group, which examined at least 1 muscle fitness evaluation index in individuals aged 5–18 years were included. Articles were evaluated using the Jaded scale. Weighted-mean standardized mean differences (SMDs) were calculated using random-effects models. Twenty-one studies and 2267 subjects were included. Physical activity had moderate effects on improving muscle fitness (SMD: 0.58–0.96, p < 0.05). Physical activity element subgroup analysis showed that high-intensity (SMD 0.68–0.99, p < 0.05) physical activity <3 times/week (SMD 0.68–0.99, p < 0.05), and <60 min/session (SMD 0.66–0.76, p < 0.01) effectively improved muscle fitness. Resistance training of ≥3 sets/session (SMD 0.93–2.90, p < 0.01) and <10 repetitions/set (SMD 0.93–1.29, p < 0.05) significantly improved muscle fitness. Low-frequency, high-intensity, and short-duration physical activity more effectively improves muscle fitness in children and adolescents. The major limitation of this meta-analysis was the low quality of included studies. The study was registered in PROSPERO with the registration number CRD42020206963 and was funded mainly by the Ministry of Education of Humanities and Social Science project, China.

It is well known that uncompensable heat stress greatly impairs endurance and team sport-related performance because an increase in the core temperature directly induces a greater magnitude of the central fatigue in the heat than in thermal neutral environments. Numerous studies have been conducted in an attempt to discover reliable cooling strategies for improving endurance performance and repeated sprint ability while exercising in the heat. Whole-body pre-cooling has been shown to improve endurance performance in both dry and humid heat. Despite this, the reduction in thermal perceptions associated with pre-cooling gradually narrows during intense exercise. Hence, effective per-cooling strategies to improve athletic performance in the heat are required. Unfortunately, due to practical issues, adopting pre-cooling approaches as a per-cooling (cooling during exercise) modality to improve athletic performance is impractical. Thus, we sought to examine the impact of head, neck and face cooling on athletic performance in heat. According to current evidence, cooling the head, neck and face reduced local skin temperature in the areas where cooling was applied, resulting in improved local perceptual sensations. In the heat, neck cooling during exercise improves athletic performance in both endurance and team sports athletes. Furthermore, from a practical standpoint, neck cooling is preferred over head, face and combined head/face and neck cooling for both endurance and team sport athletes in the heat. Nonetheless, for all athletes who have access to water, face cooling is a recommended cooling strategy. There is a lack of research on the systematic selection of per-cooling modalities to improve athletic performance based on environmental conditions and the nature of sports. In addition, powerful but portable head, neck and face cooling systems are urgently needed to assist athletes in improving their performance in hot conditions.

Introduction: Caffeinated chewing gum, known for its rapid absorption, has not been previously studied for its effects on maximal strength and muscular endurance in resistance exercise. The aim of this study was to determine the efficacy of caffeinated chewing gum on maximal strength and muscular endurance during bench press and back squat exercises.Methods: In a randomized, double-blind design, 16 resistance-trained males (age: 21.6 ± 2.0 years, height: 176.8 ± 6.1 cm, mass: 79.6 ± 8.8 kg) chewed either caffeinated gum (3 mg/kg) or a placebo gum on two occasions, 1 week apart. After a standardized warm-up, participants chewed the gum for 5 min before performing maximal strength test (one-repetition maximum [1RM]) and muscular endurance test (60% 1RM repetitions to failure) for bench press and back squat exercises. 1RM, number of repetitions, ratings of perceived exertion and pain perception were assessed.Results: Caffeinated chewing gum significantly improved 1RM in both bench press (105.3 ± 14.5 vs. 100.3 ± 13.4 kg, +5.0% [95% confidence interval (CI): 3.7–6.3%], p < 0.01) and back squat (172.3 ± 20.2 vs. 161.9 ± 22.3 kg, +6.8% [95%CI: 4.1–9.5%], p < 0.01) exercises with small effect size (Cohen’s d: 0.36 [95%CI: 0.09–0.63] and 0.49 [95%CI: 0.22–0.76], respectively), despite similar levels of pain perception and RPE (p > 0.05). It also increased the number of repetitions in both bench press (20 ± 5 vs. 17 ± 4, +18.8% [95%CI: 11.5–26.1%], p < 0.01) and back squat (37 ± 11 vs. 28 ± 8, +33.3% [95%CI: 23.1–43.4%], p < 0.01) exercises with moderate-to-large effect size (Cohen’s d: 0.76 [95%CI: 0.48–1.03] and 0.89 [95%CI: 0.60–1.16], respectively), despite similar levels of pain perception and RPE (p > 0.05).Discussion: Caffeinated chewing gum (3 mg/kg) improved both maximal strength and muscular endurance during bench press and back squat exercises in resistance-trained men. This approach offers a practical and time-efficient method to improve training performance while minimizing the risk of side effects.

Background: This study examined the effects of caffeine on movement velocity and power output during resistance exercises and explored moderating factors influencing these effects.Methods: A systematic search of five databases was conducted through June 2025. A random-effects model was used to assess the effect of caffeine on muscular power-related variables, such as bar velocity and power output, during resistance exercises with a fixed number of repetitions. Subgroup analyses were performed based on sex, caffeine dose, habitual caffeine consumption, muscle group, and load.Results: Twelve studies comprising 230 participants were included. Caffeine significantly improved mean velocity (SMD = 0.42, 95% CI: 0.19–0.65, p < 0.05, I² = 85%) and mean power output (SMD = 0.21, 95% CI: 0.12–0.30, p < 0.05, I² = 14%) during resistance exercises. Greater improvements in mean velocity were observed in males (SMD: 0.56 vs. 0.22), and habitual caffeine consumption < 3 mg/kg/day (SMD: 0.87 vs. 0.21) (all p < 0.01 for subgroup comparisons). Furthermore, although caffeine increased mean velocity at all caffeine doses (SMD: 0.31–0.78), muscle groups (SMD: 0.32–0.54) and loads (SMD: 0.37–0.49) (all p < 0.01), no significant differences were observed between subgroups (all p > 0.01 for subgroup comparison).Conclusion: Caffeine ingestion enhances movement velocity and power output during resistance exercises, regardless of load. These benefits were more pronounced in males, at higher caffeine doses, among low habitual caffeine consumers, and during lower-body exercises.Systematic review registration: https://www.crd.york.ac.uk/PROSPERO/view/CRD42024616920.

Purpose: This study systematically reviewed the literature on elite rowers’ training-intensity distribution (TID), volume, periodization, physiological determinants, and performance characteristics. Methods: Three electronic databases (Scopus, PubMed, and Web of Science) were searched using relevant terms. Studies investigating and detailing training load (TID, volume, and periodization) and reporting data of physiological determinants or performance in elite rowers were included. Results: Nine studies (N = 82 participants) met the inclusion criteria. Training volume varied between 10 and 31 h·wk^–1, typically being between 14 and 20 h·wk^–1. The pyramidal TID pattern, which involves a progressive reduction in training volume from zone 1 (intensity at or below lactate threshold [LT1]) to zone 2 (intensity between LT1 and LT2, corresponding to blood lactate levels between 2 and 4 mmol·L⁻¹) and zone 3 (intensity above LT2) was most commonly used by elite rowers. Flexible seasonal TIDs were observed, whereby the combined training in zones 2 and 3 approached or exceeded 20%, and zone 1 training comprised more than 50%. Flexible TIDs were associated with greater improvements in physiological determinants and performance. Elite rowers typically employed a traditional periodization model, progressively transitioning from pyramidal toward a polarized TID model as they moved from preparation to competition phases. Conclusions: Elite rowers most commonly adopted a seasonal pyramidal model with variable volume. No evidence suggests that a particular TID or periodization model has a significant advantage. Conversely, TID models do not seem to differentiate training adaptations in rowing training, but specific TID percentages might.