Caffeine and sport.

Caffeine is a trimethylxanthine found in coffee and several other foods and beverages. Its stimulatory effects make it an interesting strategy to boost performance for athletic populations. Scientific evidence supports its efficacy to improve high-intensity endurance exercise, explosive and high-intensity efforts, resistance exercise, team sports and combat sports, though individual variation in the ergogenic response to caffeine exists. Supplementation can be taken in many forms including dissolved in water, via capsules, coffee, energy drinks and caffeinated gum; ingestion via capsules, dissolved in water or in caffeinated gum appear to be most effective. Variability in the exercise response following caffeine supplementation may be explained by genetic factors or habitual caffeine consumption. Caffeine is an excellent supplement for athletes looking to improve their exercise performance, though some consideration of side-effects and impact on sleep are warranted.

Performing moderate to severe activity is safe and tolerable for healthy youth while wearing a cloth facemask.

OBJECTIVE: To investigate if a cloth facemask could affect physiological and perceptual responses to exercise at distinct exercise intensities in healthy young individuals. METHODS: Nine participants (sex, female/male: 6/3; age: 13±1 years; VO2peak: 44.5±5.5 mL/kg/min) underwent a progressive square-wave test at four intensities: (1) 80% of ventilatory anaerobic threshold (VAT), (2) VAT, and (3) 40% between VAT and [Formula: see text] wearing a triple-layered cloth facemask or not. Participants then completed a final stage to exhaustion at a running speed equivalent to the maximum achieved during the cardio-respiratory exercise test (Peak). Physiological, metabolic, and perceptual measures were measured. RESULTS: Mask did not affect spirometry (forced vital capacity, peak expiratory flow, forced expiratory volume; all p≥0.27), respiratory (inspiratory capacity, end-expiratory volume [EELV] to functional vital capacity ratio, EELV, respiratory frequency [Rf], tidal volume [VT], Rf/VT, end-tidal carbo dioxide pressure, ventilatory equivalent to carbon dioxide ratio; all p≥0.196), hemodynamic (heart rate, systolic and diastolic blood pressure; all p>0.41), ratings of perceived exertion (p = 0.04) or metabolic measures (lactate; p = 0.78) at rest or at any exercise intensity. CONCLUSIONS: This study shows that performing moderate to severe activity is safe and tolerable for healthy youth while wearing a cloth facemask. TRIAL REGISTRATION: ClinicalTrials.gov: NCT04887714.

A Cloth Facemask Causes No Major Respiratory or Cardiovascular Perturbations During Moderate to Heavy Exercise.

PURPOSE: Investigate whether a cloth facemask could affect physiological and perceptual responses to exercise at distinct exercise intensities in untrained individuals. METHODS: Healthy participants (n = 35; 17 men, age 30 [4] y, and 18 women, age 28 [5] y) underwent a progressive square wave test at 4 intensities: (1) 80% of ventilatory anaerobic threshold; (2) ventilatory anaerobic threshold; (3) respiratory compensation point; and (4) exercise peak (Peak) to exhaustion, 5-minute stages, with or without a triple-layered cloth facemask (Mask or No-Mask). Several physiological and perceptual measures were analyzed. RESULTS: Mask reduced inspiratory capacity at all exercise intensities (P < .0001). Mask reduced respiratory frequency (P = .001) at Peak (-8.3 breaths·min-1; 95% confidence interval [CI], -5.8 to -10.8), respiratory compensation point (-6.9 breaths·min-1; 95% CI, -4.6 to -9.2), and ventilatory anaerobic threshold (-6.5 breaths·min-1; 95% CI, -4.1 to -8.8), but not at Baseline or 80% of ventilatory anaerobic threshold. Mask reduced tidal volume (P < .0001) only at respiratory compensation point (-0.5 L; 95% CI, -0.3 to -0.6) and Peak (-0.8 L; 95% CI, -0.6 to -0.9). Shallow breathing index was increased with Mask only at Peak (11.3; 95% CI, 7.5 to 15.1). Mask did not change HR, lactate, ratings of perceived exertion, blood pressure, or oxygen saturation. CONCLUSIONS: A cloth facemask reduced time to exhaustion but had no major impact on cardiorespiratory parameters and had a slight but clinically meaningless impact on respiratory variables at higher intensities. Moderate to heavy activity is safe and tolerable for healthy individuals while wearing a cloth facemask. CLINICALTRIALS: gov: NCT04887714.

Can I Have My Coffee and Drink It? A Systematic Review and Meta-analysis to Determine Whether Habitual Caffeine Consumption Affects the Ergogenic Effect of Caffeine.

OBJECTIVE: The aim was to quantify the proportion of the literature on caffeine supplementation that reports habitual caffeine consumption, and determine the influence of habitual consumption on the acute exercise response to caffeine supplementation, using a systematic review and meta-analytic approach. METHODS: Three databases were searched, and articles screened according to inclusion/exclusion criteria. Three-level meta-analyses and meta-regression models were used to investigate the influence of habitual caffeine consumption on caffeine's overall ergogenic effect and within different exercise types (endurance, power, strength), in men and women, and in trained and untrained individuals. Sub-analyses were performed according to the following: acute relative dose (< 3, 3-6, > 6 mg/kg body mass [BM]); whether the acute caffeine dose provided was lower or higher than the mean daily caffeine dose; and the caffeine withdrawal period prior to the intervention (< 24, 24-48, > 48 h). RESULTS: Sixty caffeine studies included sufficient information on habitual consumption to be included in the meta-analysis. A positive overall effect of caffeine was shown in comparison to placebo (standard mean difference [SMD] = 0.25, 95% confidence interval [CI] 0.20-0.30; p < 0.001) with no influence of relative habitual caffeine consumption (p = 0.59). Subgroup analyses showed a significant ergogenic effect when the caffeine dose was < 3 mg/kg BM (SMD = 0.26, 95% CI 0.12-0.40; p = 0.003) and 3-6 mg/kg BM (SMD = 0.26, 95% CI 0.21-0.32; p < 0.0001), but not > 6 mg/kg BM (SMD = 0.11, 95% CI - 0.07 to 0.30; p = 0.23); when the dose was both higher (SMD = 0.26, 95% CI 0.20-0.31; p < 0.001) and lower (SMD = 0.21, 95% CI 0.06-0.36; p = 0.006) than the habitual caffeine dose; and when withdrawal was < 24 h, 24-48 h, and > 48 h. Caffeine was effective for endurance, power, and strength exercise, with no influence (all p ≥ 0.23) of relative habitual caffeine consumption within exercise types. Habitual caffeine consumption did not modify the ergogenic effect of caffeine in male, female, trained or untrained individuals. CONCLUSION: Habitual caffeine consumption does not appear to influence the acute ergogenic effect of caffeine.

Nonplacebo Controls to Determine the Magnitude of Ergogenic Interventions: A Systematic Review and Meta-analysis.

INTRODUCTION: Placebos are used as a control treatment that is meant to be indistinguishable from the active intervention. However, where substantive placebo effects may occur, studies that do not include a nonplacebo control arm may underestimate the overall effect of the intervention (active plus placebo components). This study aimed to determine the relative magnitude of the placebo effect associated with nutritional supplements (caffeine and extracellular buffers) by meta-analyzing data from studies containing both placebo and nonplacebo control sessions. METHODS: Bayesian multilevel meta-analysis models were used to estimate pooled effects and express the placebo effect as a percentage of the overall intervention effect. RESULTS: Thirty-four studies were included, with the median pooled effect size (ES0.5) indicating a very small (ES0.5 = 0.09 (95% credible interval (CrI), 0.01-0.17)) improvement in the performance of placebo compared with control. There was no moderating effect of exercise type (capacity or performance), exercise duration, or training status. The comparison between active intervention and control indicated a small to medium effect (ES0.5 = 0.37 (95% CrI, 0.20-0.56)). Expressed in relative terms, the placebo effect was equivalent to 25% (75% CrI, 16%-35%) and 59% (75% CrI, 34%-94%) of the total intervention effect for buffers and caffeine. CONCLUSIONS: These results demonstrate a very small but potentially important placebo effect with nutritional supplementation studies. A substantive proportion of supplement effects may be due to placebo effects, with the relative proportion influenced by the magnitude of the overall ergogenic effect. Where feasible, intervention studies should use nonplacebo control-arm comparators to identify the proportion of the effect estimated to come from placebo effects and avoid underestimating the overall benefits that the physiological plus psychobiological aspects associated with an intervention provide in the real world.

Can the Skeletal Muscle Carnosine Response to Beta-Alanine Supplementation Be Optimized?

Carnosine is an abundant histidine-containing dipeptide in human skeletal muscle and formed by beta-alanine and L-histidine. It performs various physiological roles during exercise and has attracted strong interest in recent years with numerous investigations focused on increasing its intramuscular content to optimize its potential ergogenic benefits. Oral beta-alanine ingestion increases muscle carnosine content although large variation in response to supplementation exists and the amount of ingested beta-alanine converted into muscle carnosine appears to be low. Understanding of carnosine and beta-alanine metabolism and the factors that influence muscle carnosine synthesis with supplementation may provide insight into how beta-alanine supplementation may be optimized. Herein we discuss modifiable factors that may further enhance the increase of muscle carnosine in response to beta-alanine supplementation including, (i) dose; (ii) duration; (iii) beta-alanine formulation; (iv) dietary influences; (v) exercise; and (vi) co-supplementation with other substances. The aim of this narrative review is to outline the processes involved in muscle carnosine metabolism, discuss theoretical and mechanistic modifiable factors which may optimize the muscle carnosine response to beta-alanine supplementation and to make recommendations to guide future research.