Impact of Caffeine Intake Strategies on Heart Rate Variability During Post-Exercise Recovery: A Systematic Review and Meta-Analysis.

OBJECTIVES: The objective of this systematic review and meta-analysis is to evaluate the influence of caffeine (CAF) intake strategies, taking into account their form, timing, and dosage, on heart rate variability (HRV) indices in the post-exercise recovery period. METHODS: The meta-analysis adhered to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines and is registered in the PROSPERO database (CRD42023425885). A comprehensive literature search was carried out across MEDLINE, Web of Science, LILACS, and SCOPUS, concluding in May 2023. We concentrated on randomized clinical trials comparing CAF supplementation effects to placebo on HRV indices post-exercise in active adults aged 18 and above. The primary endpoint was the assessment of HRV indices, measured both prior to and following exercise. RESULTS: Of the 10 studies included, 7 were used for the meta-analysis, and all contributed to the systematic review. The research explored a variety of CAF strategies, spanning different forms (capsule, drink, gum), times (10, 45, 60 min) and doses (2.1 to 6.0 mg/kg). The outcomes revealed no substantial variations between the placebo and CAF conditions in terms of both the square root of the average of successive squared differences between adjacent RR intervals (RMSSD) (standardized mean difference (SMD) -0.03, 95% CI -0.265 to 0.197, p=0.77) and high frequency (HF) index (SMD -0.061, 95% CI -0.272 to 0.150, p=0.57). Furthermore, metaregression analysis, employing a fixed-effects model and accounting for the administered CAF doses, revealed no significant correlation between caffeine doses and HRV indices (p>0.05). CONCLUSION: In conclusion, there is moderate-certainty evidence suggesting that different CAF intake strategies, encompassing aspects such as form, time, and dose, do not have a significant impact on HRV indices recovery post-exercise (i.e., vagal modulation).

Caffeine increases performance and leads to a cardioprotective effect during intense exercise in cyclists.

The present study was designed to investigate the effects of different caffeine dietary strategies to compare the impact on athletic performance and cardiac autonomic response. The order of the supplementation was randomly assigned: placebo(4-day)-placebo(acute)/PP, placebo(4-day)-caffeine(acute)/PC and caffeine(4-day)-caffeine(acute)/CC. Fourteen male recreationally-trained cyclists ingested capsules containing either placebo or caffeine (6 mg kg-1) for 4 days. On day 5 (acute), capsules containing placebo or caffeine (6 mg kg-1) were ingested 60 min before completing a 16 km time-trial (simulated cycling). CC and PC showed improvements in time (CC vs PP, Δ - 39.3 s and PC vs PP, Δ - 43.4 s; P = 0.00; ƞ2 = 0.33) and in output power (CC vs PP, Δ 5.55 w and PC vs PP, Δ 6.17 w; P = 0.00; ƞ2 = 0.30). At the final of the time-trial, CC and PC exhibited greater parasympathetic modulation (vagal tone) when compared to the PP condition (P < 0.00; ƞ2 = 0.92). Our study provided evidence that acute caffeine intake (6 mg∙kg-1) increased performance (time-trial) and demonstrated a relevant cardioprotective effect, through increased vagal tone.

Status de peso de escolares: prevalência e combinação de excesso de peso e obesidade abdominal / Childhood weight status: prevalence and combination of overweight and abdominal obesity

Identificar a prevalência de excesso de peso e obesidade abdominal de forma isolada e combinada em escolares de 6 a 10 anos de idade. Participaram do estudo 1267 escolares do município de Macaé, RJ, Brasil. Os dados antropométricos analisados foram a massa corporal, a estatura, e a perimetria da cintura (PC). Os critérios da Organização Mundial da Saúde (OMS) foram usados para definir o sobrepeso e a obesidade. A obesidade abdominal (OA) foi estimada pela relação cintura/estatura (RCEst) ≥0,50. A prevalência de excesso de peso e obesidade nos escolares foi de 33,8% e 16,4%, respectivamente.A prevalência de OA foi de 22,7%, sendo 11,9% meninas e 10,8% meninos (p>0,05). Verificamos que 37,7 %das crianças com sobrepeso apresentam OA, sendo mais presente entre as meninas em comparação com os meninos (50% vs. 26,3%, respetivamente; p<0,05). Entre as crianças obesas, 93,7% apresentaram OA. O status de peso dos escolares esteve acompanhado pela elevada prevalência de excesso de peso e pela presença combinação de obesidade e OA, encontradas em ambos os sexos e em todas as idades.

To identify the prevalence of overweight and abdominal obesity in an isolated and combined way in schoolchildren aged 6 to 10 years old. 1267 schoolchildren from Macaé, RJ, and Brazil participated in the study. The anthropometric data analyzed were body mass, height, and waist circumference (WC). The World Health Organization (WHO) criteria were used to define overweight and obesity. Abdominal obesity (AO) was estimated by the waist / height ratio (WHtR) ≥ 0.50. The prevalence of overweight and obesity in schoolchildren was 33.8% and 16.4%, respectively. The prevalence of AO was 22.7%, 11.9% girls and 10.8% boys (p> 0.05). We found that 37.7% of overweight children have AO, being more present among girls when compared to boys (50% vs. 26.3%, respectively; p <0.05). Among obese children, 93.7% had AO. The students' weight status was accompanied by the high prevalence of overweight and the presence of a combination of obesity and AO, found in both sexes and at all ages.

Caffeine Supplementation for 4 Days Does Not Induce Tolerance to the Ergogenic Effects Promoted by Acute Intake on Physiological, Metabolic, and Performance Parameters of Cyclists: A Randomized, Double-Blind, Crossover, Placebo-Controlled Study.

The present study investigated whether the caffeine supplementation for four days would induce tolerance to the ergogenic effects promoted by acute intake on physiological, metabolic, and performance parameters of cyclists. A double-blind placebo-controlled cross-over design was employed, involving four experimental trials; placebo (4-day)-placebo (acute)/PP, placebo (4-day)-caffeine (acute)/PC, caffeine (4-day)-caffeine (acute)/CC and caffeine (4-day)-placebo (acute)/CP. Fourteen male recreationally-trained cyclists ingested capsules containing either placebo or caffeine (6 mg∙kg-1) for 4 days. On day 5 (acute), capsules containing placebo or caffeine (6 mg∙kg-1) were ingested 60 min before completing a 16 km time-trial (TT). CC and PC showed improvements in time (3.54%, ES = 0.72; 2.53%, ES = 0.51) and in output power (2.85%, ES = 0.25; 2.53%, ES = 0.20) (p < 0.05) compared to CP and PP conditions, respectively. These effects were accompanied by increased heart rate (2.63%, ES = 0.47; 1.99%, ES = 0.34), minute volume (13.11%, ES = 0.61; 16.32%, ES = 0.75), expired O2 fraction (3.29%, ES = 0.96; 2.87, ES = 0.72), lactate blood concentration (immediately after, 29.51% ES = 0.78; 28.21% ES = 0.73 recovery (10 min), 36.01% ES = 0.84; 31.22% ES = 0.81), and reduction in expired CO2 fraction (7.64%, ES = 0.64; 7.75%, ES = 0.56). In conclusion, these results indicate that caffeine, when ingested by cyclists in a dose of 6 mg∙kg-1 for 4 days, does not induce tolerance to the ergogenic effects promoted by acute intake on physiological, metabolic, and performance parameters.

Cardiopulmonary Performance During Maximal Exercise in Soccer Players with Alterations in Renal Function.

The aim of this study was to evaluate the curves of cardiorespiratory variables during cardiopulmonary exercise testing (CPET) in soccer players who had acute alterations in the glomerular filtration rate (GFR) after performing the pre-season training protocol. Sixteen male professional soccer players (25 ± 3 years; 179 ± 2 cm; and 77 ± 6 kg) were evaluated for oxygen uptake (VO2), heart rate (HR) and pulse relative oxygen (relative O2 Pulse) curves with intervals corresponding to 10% of the total duration of CPET. Athletes were grouped according to the GFR and classified as decreased GFR (dGFR; n = 8) and normal GFR (nGFR; n = 8). Athletes from the dGFR group exhibited lower VO2 values (p < 0.05) when 90% (dGFR 49.8 ± 4.0 vs. nGFR 54.4 ± 6.1 ml·kg-1·min-1) and 100% (dGFR 52.6 ± 4.1 vs. nGFR 57.4 ± 5.9 ml·kg-1·min-1) of the test was complete; HR high values (p < 0.05) when 90% (dGFR 183.7 ± 5.1 vs. nGFR 176.6 ± 4.8 bpm-1) and 100% (dGFR 188.1 ± 5.0 vs. nGFR 180.8 ± 4.8 bpm-1) of the test was complete; and lower relative O2 Pulse values (p < 0.05) when 70% (dGFR 25.6 ± 8.4 vs. nGFR 27.9 ± 9.7 ml·beat-1·kg-1), 80% (dGFR 26.6 ± 8.8 vs. nGFR 29.1 ± 10.0 ml·beat-1·kg-1), 90% (dGFR 27.1 ± 9.0 vs. nGFR 30.8 ± 10.6 ml·beat-1·kg-1) and 100% (dGFR 28 ± 9.2 vs. nGFR 31.8 ± 10.9 ml·beat-1·kg-1) of the test was complete. A correlation was found (r = -0.66, R2 = 0.44, p = 0.00) between lower VO2 peak and elevated levels of urinary protein excretion. In conclusion, soccer players with reduced kidney function after performing the pre-season training protocol also presented alterations in cardiopulmonary variables. We suggest that monitoring of renal function may be used to identify less conditioned soccer players.

Alterações dos níveis séricos de creatinina, ácido úrico, creatina kinase e da taxa de filtração glomerular em corredores de "rua" / Changes in serum creatinine, uric acid, creatine kinase and glomerular filtration in street runners

As estratégias adotadas pelos corredores de "rua", durante as provas, sofrem interferência da distância da corrida e dos níveis técnico e físico dos competidores. Assim,o objetivo deste estudo foi de examinar os efeitos bioquímicos da Creatinina (C), Ácido Úrico (AU), Creatina Kinase (CK) e da Taxa de Filtração Glomerular (TFG) provocados por uma prova de corrida de "rua" de 6 (seis) Km. Participaram n=(15) atletas masculinos (40,53±8,65 anos) separados em 3 grupos: Grupo 1 Melhores Tempos (G1MT) n=5; Grupo 2 Tempos Intermediários (G2TI) n =5; Grupo 3 Piores Tempos (G3PT) n=5. Foram coletadas amostras de sangue 30 min antes e imediatamente após a corrida. Os dados foram analisados através da ANOVA Two-Way, Wilcoxon e Mann Whitney. Consideraram-se os níveis significativos (p<0,05). Os resultados permitem concluir que ocorreram aumentos significativos intragrupos nas atividades séricas de (C) no G1MT pré: 1,18±0,04 mg.dL-¹ pós: 1,60±0,15 mg.dL-¹; G2TI pré: 1,04±0,15 mg.dL-¹ pós: 1,56 ±0,21 mg.dL-¹; G3PT pré 1,08±0,13 mg.dL-¹ pós 1,52±0,32 mg.dL-¹ e no (AU) G1MT pré: 3,80±0,75 mg.dL-¹ pós 4,56±0,94 mg.dL-¹; G2TI pré 4,36±1,62 mg.dL-¹ pós 5,0 ±1,69 mg.dL-¹; G3PT pré 4,62±1,08 mg.dL-¹ pós: 5,42±0,86 mg.dL-¹, enquanto a (CK) e a (TFG) não apresentaram diferença significativa.

The strategies adopted by corridors "street" during the evidence from interference of the race distance and levels of technical and physical competition. The objective of this study was to examine the biochemical effects of Creatinine (C), Uric Acid (AU), Creatine Kinase (CK) and Glomerular Filtration Rate (GFR) caused by a test run of "street" of 6 (six) Km participated n=(15) male athletes (40.53 ± 8.65 years) divided into three groups: Group 1 Best Times (G1MT) n = 5, Group 2 Intermediate Times (G2TI) n = 5; Group 3 Times Worst (G3PT) n = 5. Blood samples were collected 30 min before and immediately after the race. Data were analyzed by Two-Way ANOVA, Wilcoxon and Mann Whitney test. It was considered significant levels (p<0.05). The results showed that there were significant increases in serum activities of intra-group (C) in G1MT before: 1,18±0,04 mg.dL-¹ after: 1.60±0.15 mg.dL-¹; G2TI before: 1,04±0,15 mg.dL-¹ after: 1,56±0,21 mg.dL-¹; G3PT before: 1,08±0,13 mg.dL-¹ after: 1,52±0,32 mg.dL-¹ and (AU) G1MT before: 3,80±0,75 mg.dL-¹ after: 4,56±0,94 mg.dL-¹; G2TI before: 4,36±1,62 mg.dL-¹ after: 5,0±1,69 mg.dL-¹; G3PT before: 4,62±1,08 mg.dL-¹ after: 5,42±0,86 mg.dL-¹, while (CK) and (GFR) showed no significant difference.

Efeito da estimulalção cortical na variável tempo de reação e performance hábil-motriz-cognitiva em jovens atletas de futebol / Effect of the cortical stimulation in the variable reaction of time and skilled-motor-cognitive performance in young soccer athletes

O estudo verificou-se o efeito da estimulação cortical no tempo de reação e eficiência hábil-motriz-cognitiva em atletas de futebol, pré e pós-estimulação cortical A amostra de (N=20) atletas masculino de futebol da categoria infantil. Os participantes foram divididos em 2 grupos, controle e experimental, sendo o grupo experimental submetido à estimulação. Foram realizadas 10 sessões, de 20'. Os dados do teste foram tratados através de uma análise de variância paramétrica (ANOVA) two way. A média de acertos / pelo tempo de reação obteve ganho significativo para o grupo experimental quando comparada ao controlo no momento pós-teste (P<0.05). No grupo experimental obteve ganho significativo na melhora do tempo de reação quando comparado ao grupo controle (p<0.05). No intra-grupos, o grupo que recebeu o treinamento combinado, obteve melhoras significativas comparados o pré e pós-teste (p<0,05). Concluiu-se que o treinamento combinado pode-se aprimorar a aprendizagem motora em diversas áreas de conhecimento e esporte.

The study was verified the effect of the cortical stimulation in the time of reaction and skilled motor cognitive efficiency in soccer athletes, before and cortical after stimulation the sample of (N=20) athletes masculine of soccer of the infantile category. The participants were divided in 2 groups, control and experimental, being the experimental group submitted to the stimulation. 10 sessions, of 20'. The data originating from of the test were treated through a parametric variance analysis (ANOVA) two way. The average of successes / for the time of reaction obtained significant earnings for the experimental group when compared to the control in the moment after-tests (P <0.05). In the experimental group obtained significant earnings in the improvement of the time of reaction when compared to the group controls (p <0.05). In the in groups, the group that it received the combined training, obtained significant improvements compared the before and after-test (p <0,05). It was ended that the combined training the motor learning can be perfected in several knowledge areas and sport.

Estudo comparativo de variáveis bioperacionais entre atletas de desportos de diferentes demandas / Study comparative of variables bioperational among athletes of sports of different demands

Este estudo teve por função mensurar e comparar os escores de atletas de desportos de diferentes demandas, em variáveis bioperacionais. Para tanto, selecionou-se trinta (N=30) atletas do gênero masculino, com idade entre 13 e 16 anos, sendo 15 atletas de basquetebol e 15 velocistas do atletismo. As variáveis coordenação geral, percepção cinestésica e tempo de reação motriz foram mensuradas por meio de testes aplicados na seguinte ordem, teste de Burpee, teste de Salto Percepção Cinestésica e teste de Tempo de Reação Motriz. Os dados obtidos foram tratados e analisados no programa SSPS 10. Na versão descritiva utilizou-se os escores mínimos e máximos, as médias e desvios-padrão, na estatística inferencial, o teste “t” student. O teste da hipótese do estudo teve como referência o valor de alfa p≤0,05. Os resultados apontaram o tempo de reação dos atletas de basquetebol como variável que obteve significância estatística na comparação entre grupos.

This study had the task of comparing and measuring the scores of sports athletes of different demands raised here, the basketball and athletics, in varying bioperacionais. Thirty (N = 30) athletes of the masculine gender were selected, with age between 13 and 16 years, 15 basketball athletes and 15 athletes velocitys. The variables overall coordination, cinestesic perception and reaction time, were measured by means of tests that were applied in the following order, Burpee test; Jump Cinestesic Perception and test the reaction time. Data from the testing procedures were processed and analyzed in the program SSPS 10. In the version used to the descriptive means and standard deviations for the two times of testing. In statistical inference used to test the “t” student. The test of the hypothesis of the study was to reference the value of alpha p≤0.05. The basketball athletes were pointed to have a better score in this variable. The results pointed to the reaction time of driving as the variable that has obtained statistical significance between the groups.