No Effects of Carbohydrate Ingestion on Muscle Metabolism or Performance During Short-Duration High-Intensity Intermittent Exercise.

Carbohydrates are critical for high-intensity exercise performance. However, the effects of carbohydrate supplementation on muscle metabolism and performance during short-duration high-intensity intermittent exercise remain inadequately explored. Our aim was to address this aspect in a randomized, counterbalanced, double-blinded crossover design. Eleven moderately-to-well-trained males performed high-intensity intermittent cycling receiving carbohydrate (CHO, ~55 g/h) or placebo (PLA) fluid supplementation. Three exercise periods (EX1-EX3) were completed comprising 10 × 45 s at ~105% Wmax interspersed with 135 s rest between bouts and ~20 min between periods. Repeated sprint ability (5 × 6 s sprints with 24 s recovery) was assessed at baseline and after each period. Thigh muscle biopsies were obtained at baseline and before and after EX3 to determine whole-muscle and fiber-type-specific glycogen depletion. No differences were found in muscle glycogen degradation at the whole-muscle (p = 0.683) or fiber-type-specific level (p = 0.763-0.854) with similar post-exercise whole-muscle glycogen concentrations (146 ± 20 and 122 ± 15 mmol·kg-1 dw in CHO and PLA, respectively). Repeated sprint ability declined by ~9% after EX3 with no between-condition differences (p = 0.971) and no overall differences in ratings of perceived exertion (p = 0.550). This was despite distinctions in blood glucose concentrations throughout exercise, reaching post-exercise levels of 5.3 ± 0.2 and 4.1 ± 0.2 mmol·L-1 (p < 0.001) in CHO and PLA, respectively, accompanied by fivefold higher plasma insulin levels in CHO (p < 0.001). In conclusion, we observed no effects of carbohydrate ingestion on net muscle glycogen breakdown or sprint performance during short-duration high-intensity intermittent exercise despite elevated blood glucose and insulin levels. These results therefore question the efficacy of carbohydrate supplementation strategies in high-intensity intermittent sports.

No additive effect of creatine, caffeine, and sodium bicarbonate on intense exercise performance in endurance-trained individuals.

BACKGROUND: Athletes commonly use creatine, caffeine, and sodium bicarbonate for performance enhancement. While their isolated effects are well-described, less is known about their potential additive effects. METHODS: Following a baseline trial, we randomized 12 endurance-trained males (age: 25 ± 5 years, VO2max: 56.7 ± 4.6 mL kg-1 min-1; mean ± SD) and 11 females (age: 25 ± 3 years, VO2max: 50.2 ± 3.4 mL kg-1 min-1) to 5 days of creatine monohydrate (0.3 g kg-1 per day) or placebo loading, followed by a daily maintenance dose (0.04 g kg-1) throughout the study. After the loading period, subjects completed four trials in randomized order where they ingested caffeine (3 mg kg-1), sodium bicarbonate (0.3 g kg-1), placebo, or both caffeine and sodium bicarbonate before a maximal voluntary contraction (MVC), 15-s sprint, and 6-min time trial. RESULTS: Compared to placebo, mean power output during 15-s sprint was higher following loading with creatine than placebo (+34 W, 95% CI: 10 to 58, p = 0.008), but with no additional effect of caffeine (+10 W, 95% CI: -7 to 24, p = 0.156) or sodium bicarbonate (+5 W, 95% CI: -4 to 13, p = 0.397). Mean power output during 6-min time trial was higher with caffeine (+12 W, 95% CI: 5 to 18, p = 0.001) and caffeine + sodium bicarbonate (+8 W, 95% CI: 0 to 15, p = 0.038), whereas sodium bicarbonate (-1 W, 95% CI: -7 to 6, p = 0.851) and creatine (-6 W, 95% CI: -15 to 4, p = 0.250) had no effects. CONCLUSION: While creatine and caffeine can enhance sprint- and time trial performance, respectively, these effects do not seem additive. Therefore, supplementing with either creatine or caffeine appears sufficient to enhance sprint or short intense exercise performance.

Dose-response effects of caffeine during repeated cycling sprints in normobaric hypoxia to exhaustion.

PURPOSE: With limited studies exploring the dose-response of caffeine consumption on repeated sprint ability in hypoxia, this study aimed to determine the optimal caffeine dose (low, moderate or high) during repeated sprints in hypoxia to exhaustion. METHODS: On separate visits, twelve active males randomly performed four experimental trials in normobaric hypoxia (inspired oxygen fraction: 16.5 ± 0.2%). Participants ingested placebo (PLA) or caffeine capsules (3, 6 or 9 mg/kg or LOW, MOD and HIGH, respectively) 1 h before exercise and then underwent a repeated cycling sprint test (10 s sprint/20 s active recovery) to exhaustion. Total sprint number and work done, peak and mean power output, blood lactate concentration, cardiorespiratory and perceptual responses were recorded. RESULTS: Total sprint number was greater in MOD and HIGH compared to PLA (20 ± 7 and 18 ± 8 vs. 13 ± 4; all P < 0.05), with MOD also higher than LOW (15 ± 6; P = 0.02). Total work done was greater in MOD (111 ± 40 kJ) and HIGH (100 ± 35 kJ) compared to LOW (83 ± 29 kJ) and PLA (76 ± 25 kJ) (all P < 0.05). However, there were no significant differences in total sprint number or total work done between MOD and HIGH (all P > 0.05). Blood lactate concentration was higher in both MOD and HIGH compared to PLA (all P < 0.05). However, peak and mean power outputs, fatigue index, and ratings of perceived exertion did not differ across different caffeine dosages (all P > 0.05). CONCLUSION: A moderate dose of caffeine (6 mg/kg) is the optimal amount for enhancing repeated cycling sprint ability when compared to low and high doses in moderate normobaric hypoxia.

Effects of acute and multi-day low-dose sodium bicarbonate intake on high-intensity endurance exercise performance in male recreational cyclists.

PURPOSE: This study aimed to compare the effects of acute and multi-day low-dose sodium bicarbonate (SB) intake on high-intensity endurance exercise performance. METHODS: In a randomized, double-blind, cross-over design, twelve recreational male cyclists (age: 31.17 ± 4.91 years; V ˙ O2peak: 47.98 ± 7.68 ml·kg-1·min-1) completed three endurance performance tests following acute SB (ASB, 0.2 g·kg-1 SB), multi-day SB (MSB, 0.2 g·kg-1·day-1 SB for four days), and placebo (PLA) intake. The high-intensity endurance performance was assessed with a cycling exercise test, wherein participants cycled on a bicycle ergometer at 95% of the predetermined anaerobic threshold for 30 min, followed by a time-to-exhaustion test at 110% of the anaerobic threshold. Data were analyzed using one-way and two-way repeated-measures ANOVA. RESULTS: Significant main effects of supplementation protocol were evident in pre-exercise bicarbonate concentrations (F = 27.93; p < 0.01; partial eta squared (η2) = 0.72; false discovery rate (FDR)-adjusted p value = 0.001). Prior to performance test, blood bicarbonate concentrations were significantly higher in MSB (25.78 ± 1.63 mmol·L-1 [95% CI 26.55-28.44] (p < 0.001; FDR-adjusted p value = 0.001)) and ASB (27.49 ± 1.49 mmol·L-1 [95% CI 24.75-26.81] (p < 0.001; FDR-adjusted p value = 0.007)) compared to PLA (23.75 ± 1.40 mmol·L-1 [95% CI 22.86 to 24.64]). Time-to-exhaustion increased in MSB (54.27 ± 9.20 min [95% CI 48.43-60.12]) compared to PLA (49.75 ± 10.80 min [95% CI 42.89-56.62]) (p = 0.048); however, this increase in MSB did not reach the significance threshold of 1% FDR (FDR-adjusted p value = 0.040). No significant difference was noted in exhaustion times between ASB (51.15 ± 8.39 min [95% CI 45.82-56.48]) and PLA (p > 0.05). CONCLUSION: Both acute and multi-day administration of low-dose SB improves buffering system in cyclists; nevertheless, neither intervention demonstrates sufficient efficacy in enhancing high-intensity endurance performance.

Acute effects of caffeine or quercetin ingestion on motor unit firing pattern before and after resistance exercise.

The aim of the present study was to investigate the acute effect of caffeine or quercetin ingestion on motor unit firing patterns and muscle contractile properties before and after resistance exercise. High-density surface electromyography (HDs-EMG) during submaximal contractions and electrically elicited torque in knee extensor muscles were measured before (PRE) and 60 min after (POST1) ingestion of caffeine, quercetin glycosides, or placebo, and after resistance exercise (POST2) in ten young males. The Convolution Kernel Compensation technique was used to identify individual motor units of the vastus lateralis muscle for the recorded HDs-EMG. Ingestion of caffeine or quercetin induced significantly greater decreases in recruitment thresholds (RTs) from PRE to POST1 compared with placebo (placebo: 94.8 ± 9.7%, caffeine: 84.5 ± 16.2%, quercetin: 91.9 ± 36.7%), and there were significant negative correlations between the change in RTs (POST1-PRE) and RT at PRE for caffeine (rs = - 0.448, p < 0.001) and quercetin (rs = - 0.415, p = 0.003), but not placebo (rs = - 0.109, p = 0.440). Significant positive correlations between the change in firing rates (POST2-POST1) and RT at PRE were noted with placebo (rs = 0.380, p = 0.005) and quercetin (rs = 0.382, p = 0.007), but not caffeine (rs = 0.069, p = 0.606). No significant differences were observed in electrically elicited torque among the three conditions. These results suggest that caffeine or quercetin ingestion alters motor unit firing patterns after resistance exercise in different threshold-dependent manners in males.

No Combined Effect of Caffeinated Chewing Gum and Priming Exercise on Oxygen Uptake and Muscle Near-Infrared Spectroscopy-Derived Kinetics: A Double-Blind Randomized Crossover Placebo-Controlled Trial in Cyclists.

This study aimed to investigate the effects of caffeine ingestion by chewing gum (GUMCAF) combined with priming exercise on pulmonary oxygen uptake (V˙O2) and near-infrared spectroscopy-derived muscle oxygen extraction (HHb + Mb) kinetics during cycling performed in a severe-intensity domain. Fifteen trained cyclists completed four visits: two under a placebo gum (GUMPLA) and two under GUMCAF ingestion. Each visit consisted of two square-wave cycling bouts at Δ70 intensity (70% of difference between the V˙O2 at first ventilatory threshold and V˙O2max) with duration of 6 min each and 5 min of passive rest between the bouts. The GUMPLA or GUMCAF (400 mg) was chewed for 5 min, 12 min before the first Δ70 bout in a randomized double-blind procedure. The fundamental phase and slow component of HHb + Mb and V˙O2 kinetics were evaluated. For HHb + Mb kinetics, regardless of ingested gum, priming exercise effects occurred on the time constant (GUMCAF 16.0 ± 4.0 vs. 13.9 ± 2.9 s; GUMPLA 15.7 ± 6.1 vs. 13.2 ± 2.5 s), amplitude, slow component, time delay, and mean response time parameters (p ≤ .032). For V˙O2 kinetics, there were significant effects of bouts on the amplitude, slow component, end V˙O2, and the gain kinetics parameters (p < .017). Baseline V˙O2 was higher during GUMCAF than GUMPLA (p = .020). No significant effects occurred for the interaction between gum and bout in any parameter of V˙O2 or HHb + Mb kinetics. Therefore, unlike the priming exercise in severe-intensity exercise, GUMCAF is not an effective strategy for improving V˙O2 or HHb + Mb kinetics acceleration.

Oral but Not Topical Sodium Bicarbonate Improves Repeated Sprint Performance During Simulated Soccer Match Play Exercise in Collegiate Athletes.

This study investigated the effect of oral and topical sodium bicarbonate (SB) on soccer-specific performance during simulated soccer exercise. In a block randomized, double-blind, crossover design, 10 collegiate male soccer players (stature: 181.7 ± 3.2 cm, body mass: 81.7 ± 10.5 kg) performed soccer-specific performance tests (countermovement jumps, Illinois agility, 8 × 25 m repeated sprints) throughout a 90-min soccer-specific aerobic field test (SAFT90) following 0.3 g/kg body mass SB in capsules (SB-ORAL), 0.9036 g/kg body mass PR Lotion (SB-LOTION), or placebo capsules and lotion (PLA). Soccer-specific performance tests were conducted pre-SAFT90, during half-time and post-SAFT90. Blood samples were analyzed for acid-base balance (pH; bicarbonate, HCO3-) and strong ions (sodium, Na+; potassium, K+). Average sprint times were quicker for SB-ORAL than PLA during half-time (3.7%; p = .049; g = .57) and post-SAFT90 (4.9%; p = .041; g = .66). SB-ORAL increased pH and HCO3- prewarm-up and during half-time (p < .05), and lowered K+ during half-time (p = .035) compared with PLA. SB-LOTION increased pH (p = .019) and lowered K+ (p = .012) during half-time compared with PLA. SB-LOTION increased Na+ postexercise compared with PLA (p = .008). Repeated sprint times during simulated soccer exercise improved for SB-ORAL, which might have been mechanistically underpinned by elevated blood buffering capacity and greater regulation of strong ion concentration. Consuming SB in capsules is a more effective strategy than topical SB application for improving blood buffering capacity and repeated sprint performance throughout competitive soccer matches.

Contaminants in Dietary Supplements: Toxicity, Doping Risk, and Current Regulation.

Athletes, both amateur and professional, often resort to the consumption of nutritional supplements without professional supervision and without being aware of the risks they may entail. We conducted an exhaustive literature search to determine the most common substances found as contaminants in dietary supplements. For each substance, we analyzed its mechanism of action, clinical indication, health risk, and putative use as doping agent. In addition, we evaluated the current regulation of these supplements. Contamination of nutritional supplements (accidental or intentional), especially with steroids and stimulants, is a hazardous situation. The prolonged consumption of these products without being aware of their composition can cause serious health risks and, in the case of professional athletes, a possible sanction for doping.

Caffeine Does Not Alter Performance, Perceptual Responses, and Oxidative Stress After Short Sprint Interval Training.

Despite the abundance of research investigating the efficacy of caffeine supplementation on exercise performance, the physiological and biochemical responses to caffeine supplementation during intermittent activities are less evident. This study investigated the acute effects of caffeine supplementation on measures of exercise performance, ratings of perceived exertion, and biomarkers of oxidative stress induced by an acute bout of sprint interval training. In a randomized crossover design, 12 healthy males (age: 26 ± 4 years, height: 177.5 ± 6 cm, body mass: 80.7 ± 7.6 kg) ingested 6 mg/kg of caffeine or placebo 60 min prior to performing sprint interval training (12 × 6 s "all-out sprints" interspersed by 60 s of rest). Performance scores and ratings of perceived exertion were assessed after every sprint. Blood samples were collected before supplementation, prior to and following each sprint, and 5 and 60 min after the last sprint. Caffeine had no effect on any performance measures, ratings of perceived exertion, or biomarkers of oxidative stress (p > .05). In conclusion, caffeine supplementation does not improve performance or decrease oxidative stress after an acute bout of sprint interval training.

Sodium bicarbonate and beta-alanine supplementation: Is combining both better than either alone? A systematic review and meta-analysis.

This systematic review and meta-analysis aimed to determine the effect of combined beta-alanine (BA) and sodium bicarbonate (SB) supplementation on exercise capacity and performance. Four databases (PubMed, SPORTDiscus, Web Of Science and MEDLINE) were searched using relevant terms for studies involving healthy (e.g. no chronic diseases or conditions) male or female adults of any training status (athletes, physically active and non-athletes) and that investigated BA and SB in isolation and combination at any dose on an exercise outcome. Ten studies, totalling 243 individuals, met the criteria with 12 outcomes for each nutritional supplement. No ergogenic effect was detected in this meta-analysis for BA (SMD = 0.18, 95% CI: -0.06; 0.43, p = 0.13, tau2 = 0, tau = 0, I2 = 0.0%) or SB (SMD = 0.17, 95% CI: -0.08; 0.41, p = 0.16, tau2 = 0, tau = 0, I2 = 0.0%) in isolation. However, there was a beneficial effect for the combination of BA and SB (SMD = 0.32, 95% CI: 0.07; 0.57, p = 0.02, tau2 = 0, tau = 0, I2 = 0.0%). Meta-regression identified no differences between supplementing with BA or SB separately (F = 0.58; p = 0.57). Combining BA and SB improved exercise performance, however, there was no benefit in taking these supplements individually.

A Single Dose of Beetroot Juice not Enhance Performance during Intervallic Swimming Efforts.

Despite the numerous scientific evidence on the topic, there is no clear and consistent answer that clarifies the true effects of beetroot juice (BJ) supplementation on different types of physical performance. This study examined whether an acute intake of BJ improves swimming performance, physiological variables of anaerobic metabolism, or subjective measures during high-intensity interval exercise with incomplete rest in competitive swimmers. Eighteen competitive swimmers (nine females and nine males) participated in this cross-over randomized, placebo-controlled, double-blind and counterbalanced study. In two trials, swimmers ingested BJ (70 mL, 6.4 mmol/400 mg NO3-) or placebo (PLA) (70 mL, 0.04 mmol/3 mg NO3-) three hours before a 2×6×100 m maximal effort with 40 seconds rest between repetitions and three minutes between blocks. The 100 m times showed no differences between groups (p > 0.05), but there was an interaction between block×repetition×condition (F5 = 3.10; p = 0.046; ηp2 = 0.54), indicating that the BJ group decreased the time of the sixth repetition of block2 compared to block1 (p = 0.01). Lactate concentration showed no differences between conditions (p > 0.05), but there was a main effect of block (ηp2 = 0.60) and a block×repetition interaction (ηp2 = 0.70), indicating higher values in block2 and increasing values between repetitions in block1. The subjective scales, perception of exertion (RPE) and Total Quality Recovery (TQR), showed no effects of condition (p > 0.05), but BJ swimmers had a greater TQR in the last repetitions of each block. In conclusion, a single dose of BJ did not enhance intermittent swimming performance or modified the physiological (lactate and heart rate) or subjective (RPE and TQR) variables; although there was a possible positive effect on the exercise tolerance at the end of effort.

Is caffeine mouth rinsing an effective strategy to improve physical and cognitive performance? A systematic review.

The aim of this study was to perform a systematic review on the effects of caffeine mouth rinsing on physical and cognitive performance. Following a search through 4 databases, 18 studies were found meeting the inclusion criteria (15 for physical performance and 3 for cognitive performance). All selected studies found an improvement in cognitive performance with caffeine mouth rinse. Four studies found positive effects of caffeine mouthwash on physical performance when repeated during exercise, while one study detected a positive effect with a single mouthwash before exercise, but only in a fasted state. Among these studies that showed positive effects, however, three (2 for physical performance and 1 for cognitive performance) presented fair methodological quality. There was also a variety of methodological approaches in the studies that showed no improvement in physical performance with caffeine mouth rinse, which may have influenced the potential to detect the ergogenic effect of caffeine mouth rinse. Thus, the effects of caffeine mouth rinse on physical performance are mixed, but a potential ergogenic effect might be present in a fasted state and when mouthwash is repeated during exercise. Concerning cognitive performance, caffeine mouth rinse seems to be a beneficial strategy.

Effects of creatine and caffeine ingestion in combination on exercise performance: A systematic review.

Creatine (CRE) and caffeine (CAF) have been used as ergogenic aids to improve exercise performance. The present study reviewed the current evidence supporting the additional use of CAF intake during or after the CRE loading on exercise performance. The search was carried out in eight databases, with the methodological quality of the studies assessed via the QualSyst tool. From ten studies that met the criteria for inclusion, six had strong, three moderate, and one weak methodological quality. CAF was ingested ∼1 h before the performance trial (5-7 mg.kg-1) after a CRE loading period (5-6 days with 0.3 g.kg-1.d-1) in five studies, with the combination CAF + CRE providing additional ergogenic effect compared to CRE alone in three of these studies. Furthermore, CAF was ingested daily during the CRE loading protocol in five studies, with CAF showing additive benefits compared to CRE alone only in one study (3 g.d-1 of CRE during 3 days + 6 mg.kg-1 of CAF for 3 days). The combination CAF + CRE seems to provide additional benefits to exercise performance when CAF is acutely ingested after a CRE loading. There is, however, no apparent benefit in ingesting CAF during a CRE loading period.Supplemental data for this article is available online at https://doi.org/10.1080/10408398.2021.2007470.

Load and muscle group size influence the ergogenic effect of acute caffeine intake in muscular strength, power and endurance.

INTRODUCTION: Although acute caffeine intake seems to improve muscular strength-power-endurance performance, there is scarce evidence evaluating upper vs lower-body exercises at different loads. Thus, this study aimed to examine the effects of acute caffeine intake on upper and lower-body muscular strength, power and endurance performance at different loads. METHODS: Twenty resistance-trained athletes (male/female: 10/10; age: 23 ± 4 years; body mass: 70.6 ± 15.1) participated in a double-blind, placebo-controlled, cross-over and randomized study. Participants were provided with either 3 mg/kg of body mass of caffeine or maltodextrin (placebo). Sixty minutes after ingestion, they performed muscular strength and power assessment for bench press and back squat exercise at 25%, 50%, 75% and 90% 1-repetition-maximum (1RM), performing 3, 2, 1 and 1 repetitions respectively, followed by muscular endurance assessment for both exercises at 65% and 85% 1RM performing until task failure. Isometric handgrip, isometric mid-thigh pull and vertical jump tests were also performed. RESULTS: In muscular strength and power, compared to placebo, caffeine improved mean velocity (P = 0.045; pη2 = 0.101), mean power (P = 0.049; pη2 = 0.189) and rate of force development (RFD, P = 0.032; pη2 = 0.216), particularly in back squat exercise at 75% and 90% 1RM where mean velocity increased by 5-7% (P = 0.48-0.038; g = 0.348-1.413), mean power by 6-8% (P = 0.050-0.032; g = 0.547-0.818) and RFD by 17-97% (P = 0.042-0.046; g = 1.436-1.196). No differences were found in bench press exercise. In muscular endurance, caffeine improved the number of repetitions in all exercises and loads (P = 0.003; pη2 = 0.206), but only in back squat exercise at 85% 1RM, caffeine increased mean and peak velocity (8-9%, P = 0.006-0.004; g = 2.029-2.075), mean and peak power (10-13%, P = 0.006-0.003; g = 0.888-1.151) and force peak (3%, P = 0.009; g = 0.247). CONCLUSIONS: Acute caffeine intake (3 mg/kg) improved muscular strength, power and endurance performance, revealing a more pronounced effect at high-loads (≥ 75% 1RM) and in lower-body (back squat) than in upper-body exercise (bench press) according to muscle group size.

Are Dietary Supplements a Gateway to Doping? A Retrospective Survey of Athletes' Substance Use.

Background: It is proposed that the use of dietary supplements might lead to the use of doping substances. This has been termed the gateway hypothesis. However, within an athletic sample, no research has examined the order in which these substances are consumed and what may explain the progression from dietary supplement use to doping. Objective: To identify whether dietary supplement use precedes doping and examine what moderates the dietary supplement-doping relationship. Methods: Competitive athletes (N=1,081, 42.0% female; Age=29.3±10.8 years) completed an online survey measuring dietary supplement use, doping use, doping subjective norms and age of using a supplement and/or doping substance. Results: Dietary supplement users were 11 times more likely to dope than non-users (OR=11.28, 95% CI = 2.72 to 46.77). Age for first use of a dietary supplement was younger than use of a doping substance (mean difference=-4.5±5.1 years old, p<0.001, d=0.90). Over three-quarters of doping users reported using a dietary supplement first (77.1%), whereas a small proportion of athletes started using dietary supplements and doping at the same time (12.5%) and some used doping substances before using dietary supplements (10.4%). Moderation analysis revealed that dietary supplement users may be more likely to dope because of a more favourable social acceptance of using prohibited substances than non-users. Conclusions: Data suggest that dietary supplement use is more likely to precede doping. However, not all doping users begin with using dietary supplements, which highlights the importance of measuring the temporal order of dietary supplement and doping use in future research.

Acute effects of two caffeine doses on bar velocity during the bench press exercise among women habituated to caffeine: a randomized, crossover, double-blind study involving control and placebo conditions.

PURPOSE: The main goal of this study was to evaluate the effectiveness of two different doses of caffeine (3 and 6 mg/kg) to enhance bar velocity during the bench press in women habituated to caffeine. METHODS: Twelve recreationally trained women (age: 23.3 ± 0.8 years, body mass: 60.7 ± 5.7 kg, bench press one-repetition maximum (1RM): 44.3 ± 7.8 kg, daily caffeine ingestion: 5.7 ± 2.0 mg/kg/day) participated in a randomized double-blind experimental design. Each participant performed four different experimental sessions: after no supplementation (control, CON), after ingesting 3 and 6 mg/kg of caffeine (CAF-3 and CAF-6, respectively), or after ingesting a placebo (PLAC). In each experimental session, the participants performed 3 sets of 3 repetitions of the bench press exercise at 50% 1RM. RESULTS: A two-way repeated-measures ANOVA with subsequent post hoc analyses indicated significant increases in peak velocity (p < 0.01; ES = 0.91) and mean velocity (p < 0.01; ES = 0.78) after the intake of CAF-6 compared to CON. The study did not show significant differences in bar velocity between CAF-6 and PLAC and between CAF-3 and PLAC. No significant differences in bar velocity were observed between CAF-3 and CAF-6 conditions. CONCLUSION: These results suggest that 6 mg/kg of caffeine can be an effective dose to improve power-specific training outcomes in women habituated to caffeine. However, the ergogenic effect of 6 mg/kg of caffeine may be derived from a combination of biological effects and expectancy, as this dose was only superior to the control condition with no differences over the placebo.

Effects of caffeine on rate of force development: A meta-analysis.

This review aimed to conduct a meta-analysis of studies examining the effects of caffeine on rate of force development (RFD). Ten databases were searched to find relevant studies. Risk of bias (RoB) of the included studies was evaluated. Data were analyzed in a random-effects meta-analysis. Eleven studies with "some concerns" regarding RoB were included. In the main meta-analysis, there was a significant ergogenic effect of caffeine ingestion on RFD (Hedges' g = 0.37; 95% confidence interval [CI]: 0.21, 0.52; p < 0.0001). An ergogenic effect of caffeine was also found on RFD during resistance exercises (Hedges' g = 0.49; 95% CI: 0.30, 0.67; p < 0.0001), but not during the countermovement jump test (Hedges' g = 0.18; 95% CI: -0.02, 0.39; p = 0.08), with a significant difference between the subgroups (p = 0.03). Small-to-moderate (3-5 mg/kg; Hedges' g = 0.25; 95% CI: 0.09, 0.41; p = 0.002) and moderate-to-high caffeine doses (6-10 mg/kg) enhanced RFD (Hedges' g = 0.57; 95% CI: 0.30, 0.85; p < 0.0001), even though the effects were larger with higher caffeine doses (p = 0.04). Overall, caffeine ingestion increases RFD, which is relevant given that RFD is commonly associated with sport-specific tasks. From a practical perspective: (1) individuals interested in the acute enhancement of RFD in resistance exercise may consider supplementing with caffeine; and (2) given that evaluation of RFD is most commonly used for testing purposes, caffeine ingestion (3-10 mg/kg 60 min before exercise) should be standardized before RFD assessments.

Moral values and moral identity moderate the indirect relationship between sport supplement use and doping use via sport supplement beliefs.

The Incremental Model of Doping Behaviour suggests doping grows out of the habitual use of performance-enhancing methods (e.g., sport supplements) and belief that they are necessary for performance. Importantly, in this model, doping is viewed as functional rather than moral choice. In two studies, we examined whether sport supplement use was indirectly related to doping use via sport supplement beliefs, and whether personal morality moderated this relationship. Competitive athletes (Study 1, N = 366; Study 2, N = 200) completed measures of supplement use, beliefs, and doping use. They also completed measures of moral values (Study 1) and moral identity (Study 2). In both studies, supplement use was indirectly related to doping use via beliefs. Moreover, this indirect relationship was moderated by moral values (Study 1) and moral identity (Study 2). That is, the relationship between supplement use and doping use via beliefs was negated when moral values and moral identity were high but not when they were low or moderate. Taken together, our findings suggest that sport supplement users, who believe they are necessary, are more likely to dope if they have low moral values and believe that being a moral person is unimportant to their self-image.

Evening Caffeine Did Not Improve 100-m Swimming Time Trials Performed 60 Min Post-Ingestion or the Next Morning After Sleep.

The potential ergogenic benefits of caffeine (CAF) are well known within the athletic community, often leading to its use in adolescent swimming cohorts to enhance their performance. However, it has previously been reported that CAF has sleep-disturbing effects, which could be detrimental to performance over consecutive days in multiday competitions. Moreover, the effects that evening CAF ingestion has on sleep, side effects, and next-day performances are yet to be researched in trained adolescents. In a double-blind, randomized, crossover design, eight national-level swimmers (age: 18 ± 1 years, height: 1.76 ± 0.06 cm, body mass [BM]: 69.4 ± 6.4 kg) ingested a capsule containing 3 mg/kg BM CAF or a placebo 60 min before an evening 100-m swimming time trial. The next morning, sleep was analyzed (Core Consensus Sleep Diary) and 100-m time trials were repeated. Side effects were analyzed via visual analog scales throughout the study. No differences were found for swimming performance (p = .911) in the evening (CAF: 59.5 ± 7.8 s, placebo: 59.9 ± 7.9 s, g = 0.06) or morning (CAF: 59.7 ± 7.7 s, placebo: 60.2 ± 7.9 s, g = 0.07). In addition, no group differences were found for any subjective side effects (e.g., anxiety: p = .468, tachycardia: p = .859, alertness: p = .959) or sleep parameters (e.g., sleep latency: p = .395, total sleep time: p = .574). These results question the use of a standardized 3 mg/kg BM CAF ingestion strategy for 100-m swimming time trials in trained adolescents, although objective measures may be needed to confirm that CAF does not affect sleep within this cohort.

Interaction Between Caffeine and Creatine When Used as Concurrent Ergogenic Supplements: A Systematic Review.

There is some controversy regarding the interactions between creatine (CRE) and caffeine (CAF) supplements. The aim of this systematic review was to study whether such ergogenic interaction occurs and to analyze the protocol to optimize their synchronous use. The PubMed, Web of Science, MEDLINE, CINAHL, and SPORTDiscus databases were searched until November 2021 following the PRISMA guidelines. Ten studies were included. Three studies observed that CRE loading before an acute dose of CAF before exercise did not interfere in the beneficial effect of CAF, whereas one study reported that only an acute supplementation (SUP) of CAF was beneficial but not the acute SUP of both. When chronic SUP with CRE + CAF was used, two studies reported that CAF interfered in the beneficial effect of CRE, whereas three studies did not report interaction between concurrent SUP, and one study reported synergy. Possible mechanisms of interaction are opposite effects on relaxation time and gastrointestinal distress derived from concurrent SUP. CRE loading does not seem to interfere in the acute effect of CAF. However, chronic SUP of CAF during CRE loading could interfere in the beneficial effect of CRE.