Increased prevalence of the null allele of the p.Arg577Ter variant in the ACTN3 gene in Brazilian long-distance athletes: A retrospective study.

INTRODUCTION: The phenotypic consequences of the p.Arg577Ter variant in the α-actinin-3 (ACTN3) gene are suggestive of a trade-off between performance traits for speed and endurance sports. Although there is a consistent association of the c.1729C allele (aka R allele) with strength/power traits, there is still a debate on whether the null allele (c.1729T allele; aka X allele) influences endurance performance. The present study aimed to test the association of the ACTN3 p.Arg577Ter variant with long-distance endurance athlete status, using previously published data with the Brazilian population. METHODS: Genotypic data from 203 long-distance athletes and 1724 controls were analysed in a case-control approach. RESULTS: The frequency of the X allele was significantly higher in long-distance athletes than in the control group (51.5% vs. 41.4%; p = 0.000095). The R/X and X/X genotypes were overrepresented in the athlete group. Individuals with the R/X genotype instead of the R/R genotype had a 1.6 increase in the odds of being a long-distance athlete (p = 0.012), whereas individuals with the X/X genotype instead of the R/R genotype had a 2.2 increase in the odds of being a long-distance athlete (p = 0.00017). CONCLUSION: The X allele, mainly the X/X genotype, was associated with long-distance athlete status in Brazilians.

Changes in running economy and attainable maximal oxygen consumption in response to prolonged running: The impact of training status.

During prolonged running at moderate-to-high intensity, running economy (RE) deteriorates and attainable maximal oxygen consumption (VO2max) decreases. Whether these changes appear similarly in trained and untrained runners exercising at the same relative intensity is not clear. We recruited 10 trained runners (TR) and 10 active adults (AA), and compared RE and attainable VO2max before and after 1 h of running at 70% of VO2max. Submaximal VO2 increased more (p = 0.019) in AA (0.20 ± 0.13 L min-1) than in TR (0.07 ± 0.05 L min-1). Attainable VO2max decreased in AA (-0.21 ± 0.15 L min-1, p = 0.002), but remained unchanged in TR (-0.05 ± 0.10 L min-1, p = 0.18). Relative intensity (i.e., VO2/attainable VO2max), increased more (p = 0.001) in AA (8.3 ± 4.4%) than in TR (2.6 ± 1.9%). These results demonstrate that the ability to resist changes in RE and VO2max following prolonged running is superior in trained versus untrained runners, when exercising at the same relative intensity.

The effect of a 4-week, remotely administered, post-exercise passive leg heating intervention on determinants of endurance performance.

PURPOSE: Post-exercise passive heating has been reported to augment adaptations associated with endurance training. The current study evaluated the effect of a 4-week remotely administered, post-exercise passive leg heating protocol, using an electrically heated layering ensemble, on determinants of endurance performance. METHODS: Thirty recreationally trained participants were randomly allocated to either a post-exercise passive leg heating (PAH, n = 16) or unsupervised training only control group (CON, n = 14). The PAH group wore the passive heating ensemble for 90-120 min/day, completing a total of 20 (16 post-exercise and 4 stand-alone leg heating) sessions across 4 weeks. Whole-body (peak oxygen uptake, gas exchange threshold, gross efficiency and pulmonary oxygen uptake kinetics), single-leg exercise (critical torque and NIRS-derived muscle oxygenation), resting vascular characteristics (flow-mediated dilation) and angiogenic blood measures (nitrate, vascular endothelial growth factor and hypoxia inducible factor 1-α) were recorded to characterize the endurance phenotype. All measures were assessed before (PRE), at 2 weeks (MID) and after (POST) the intervention. RESULTS: There was no effect of the intervention on test of whole-body endurance capacity, vascular function or blood markers (p > 0.05). However, oxygen kinetics were adversely affected by PAH, denoted by a slowing of the phase II time constant; τ (p = 0.02). Furthermore, critical torque-deoxygenation ratio was improved in CON relative to PAH (p = 0.03). CONCLUSION: We have demonstrated that PAH had no ergogenic benefit but instead elicited some unfavourable effects on sub-maximal exercise characteristics in recreationally trained individuals.

Caffeine ingestion compromises thermoregulation and does not improve cycling time to exhaustion in the heat amongst males.

PURPOSE: Caffeine is a commonly used ergogenic aid for endurance events; however, its efficacy and safety have been questioned in hot environmental conditions. The aim of this study was to investigate the effects of acute caffeine supplementation on cycling time to exhaustion and thermoregulation in the heat. METHODS: In a double-blind, randomised, cross-over trial, 12 healthy caffeine-habituated and unacclimatised males cycled to exhaustion in the heat (35 °C, 40% RH) at an intensity associated with the thermoneutral gas exchange threshold, on two separate occasions, 60 min after ingesting caffeine (5 mg/kg) or placebo (5 mg/kg). RESULTS: There was no effect of caffeine supplementation on cycling time to exhaustion (TTE) (caffeine; 28.5 ± 8.3 min vs. placebo; 29.9 ± 8.8 min, P = 0.251). Caffeine increased pulmonary oxygen uptake by 7.4% (P = 0.003), heat production by 7.9% (P = 0.004), whole-body sweat rate (WBSR) by 21% (P = 0.008), evaporative heat transfer by 16.5% (P = 0.006) and decreased estimated skin blood flow by 14.1% (P < 0.001) compared to placebo. Core temperature was higher by 0.6% (P = 0.013) but thermal comfort decreased by - 18.3% (P = 0.040), in the caffeine condition, with no changes in rate of perceived exertion (P > 0.05). CONCLUSION: The greater heat production and storage, as indicated by a sustained increase in core temperature, corroborate previous research showing a thermogenic effect of caffeine ingestion. When exercising at the pre-determined gas exchange threshold in the heat, 5 mg/kg of caffeine did not provide a performance benefit and increased the thermal strain of participants.

Durability in recreational runners: effects of 90-min low-intensity exercise on the running speed at the lactate threshold.

PURPOSE: Recent studies have suggested that the capability to resist deterioration of physiological characteristics could be an independent factor contributing to endurance performance. This study aimed at investigating whether prolonged low-intensity exercise induces shifts in the lactate threshold, and whether fatigue-induced changes differ between the sexes. METHODS: A total of 31 (15 females) recreational runners performed an incremental treadmill test and a 90-min low-intensity exercise (LIT90) on two separate occasions. The LIT90 was performed at 90% of the first lactate threshold speed (LT1v), derived from the incremental treadmill test. The LT1v was determined from a 5-stage (3 min) submaximal threshold test (SubmaxLT), performed before and after LIT90. The SubmaxLTs were followed by a 10/5 reactivity jump test. Respiratory gases, heart rate (HR), and HR-derived detrended fluctuation analysis alpha 1 (DFA-a1) were assessed every 15 min during the LIT90. RESULTS: A significant decrease (p < 0.01) was observed in the LT1v in females (- 5.8 ± 4.4%) and in males (- 5.3 ± 6.4%). The HR increased (p < 0.001) similarly in females (5.9 ± 3.1%) and in males (5.5 ± 3.6%) during the LIT90, while energy expenditure increased (3.1 ± 4.5%, p = 0.013) in females but remained unchanged in males (0.9 ± 3.1%). Change in DFA-a1 during the LIT90 was the only marker that correlated significantly with the relative change of LT1v (r = 0.463, p = 0.013). CONCLUSION: LIT90 induced significant decreases in the LT1v, and the changes were comparable between sexes. DFA-a1 could be a potential intra-session marker of durability.

Acute caffeine supplementation offsets the impairment in 10-km running performance following one night of partial sleep deprivation: a randomized controlled crossover trial.

INTRODUCTION: Whether acute caffeine supplementation can offset the negative effects of one-night of partial sleep deprivation (PSD) on endurance exercise performance is currently unknown. METHODS: Ten healthy recreational male runners (age: 27 ± 6 years; V ˙ O 2 max : 61 ± 9 mL/kg/min) completed 4 trials in a balanced Latin square design, which were PSD + caffeine (PSD-Caf), PSD + placebo (PSD-Pla), normal sleep (NS) + caffeine (NS-Caf) and NS + placebo (NS-Pla). 3 and 8 h sleep windows were scheduled in PSD and NS, respectively. 10-km treadmill time trial (TT) performance was assessed 45 min after caffeine (6 mg/kg/body mass)/placebo supplementation in the morning following PSD/NS. Blood glucose, lactate, free fatty acid and glycerol were measured at pre-supplementation, pre-exercise and after exercise. RESULTS: PSD resulted in compromised TT performance compared to NS in the placebo conditions by 5% (51.9 ± 7.7 vs. 49.4 ± 6.9 min, p = 0.001). Caffeine improved TT performance compared to placebo following both PSD by 7.7% (PSD-Caf: 47.9 ± 7.3 min vs. PSD-Pla: 51.9 ± 7.7 min, p = 0.007) and NS by 2.8% (NS-Caf: 48.0 ± 6.4 min vs. NS-Pla: 49.4 ± 6.9 min, p = 0.049). TT performance following PSD-Caf was not different from either NS-Pla or NS-Caf (p = 0.185 and p = 0.891, respectively). Blood glucose, lactate, and glycerol concentrations at post-exercise, as well as heart rate and the speed/RPE ratio during TT, were higher in caffeine trials compared to placebo. CONCLUSIONS: Caffeine supplementation offsets the negative effects of one-night PSD on 10-km running performance.

What if gastrointestinal complications in endurance athletes were gut injuries in response to a high consumption of ultra-processed foods? Please take care of your bugs if you want to improve endurance performance: a narrative review.

To improve performance and recovery faster, athletes are advised to eat more often than usual and consume higher doses of simple carbohydrates, during and after exercise. Sports energetic supplements contain food additives, such as artificial sweeteners, emulsifiers, acidity regulators, preservatives, and salts, which could be harmful to the gut microbiota and impair the intestinal barrier function. The intestinal barrier plays a critical function in bidirectionally regulation of the selective transfer of nutrients, water, and electrolytes, while preventing at the same time, the entrance of harmful substances (selective permeability). The gut microbiota helps to the host to regulate intestinal homeostasis through metabolic, protective, and immune functions. Globally, the gut health is essential to maintain systemic homeostasis in athletes, and to ensure proper digestion, metabolization, and substrate absorption. Gastrointestinal complaints are an important cause of underperformance and dropout during endurance events. These complications are directly related to the loss of gut equilibrium, mainly linked to microbiota dysbiosis and leaky gut. In summary, athletes must be cautious with the elevated intake of ultra-processed foods and specifically those contained on sports nutrition supplements. This review points out the specific nutritional interventions that should be implemented and/or discontinued depending on individual gut functionality.

Enhancing endurance performance with combined imagined and actual physical practice.

PURPOSE: The perception of effort exerts influence in determining task failure during endurance performance. Training interventions blending physical and cognitive tasks yielded promising results in enhancing performance. Motor imagery can decrease the perception of effort. Whether combining motor imagery and physical training improves endurance remains to be understood, and this was the aim of this study. METHODS: Participants (24 ± 3 year) were assigned to a motor imagery (n = 16) or a control (n = 17) group. Both groups engaged in physical exercises targeting the knee extensors (i.e., wall squat, 12 training sessions, 14-days), with participants from the motor imagery group also performing motor imagery. Each participant visited the laboratory Pre and Post-training, during which we assessed endurance performance through a sustained submaximal isometric knee extension contraction until task failure, at either 20% or 40% of the maximal voluntary contraction peak torque. Perceptions of effort and muscle pain were measured during the exercise. RESULTS: We reported no changes in endurance performance for the control group. Endurance performance in the motor imagery group exhibited significant improvements when the intensity of the sustained isometric exercise closely matched that used in training. These enhancements were less pronounced when considering the higher exercise intensity. No reduction in perception of effort was observed in both groups. There was a noticeable decrease in muscle pain perception within the motor imagery group Post training. CONCLUSION: Combining motor imagery and physical training may offer a promising avenue for enhancing endurance performance and managing pain in various contexts.

Acute dose-response effect of photobiomodulation therapy on 5-km running performance in trained runners: a randomized, double-blind, placebo-controlled, crossover study.

Photobiomodulation therapy (PBMT) has been advocated as a potential intervention to improve muscle performance and recovery in the health and sports context. However, the short- and long-term effects of PBMT on endurance running performance remain under-researched and controversial. The purpose of this study was to investigate the acute dose-response effect of PBMT with light-emitting diodes (LEDs) on endurance performance and rating of perceived exertion (RPE; 6-20 Borg) during a 5-km running trial in recreational runners. In a crossover design, eighteen young adult runners (28.7 ± 7.8 years) were randomized to receive 1 of 4 PBMT conditions (placebo, 300, 900, and 1260 Joules [J]) 60 min before the 5-km running trial on four occasions, separated by a 2-wk washout period. The treatments were applied to the quadriceps, hamstrings, and gastrocnemius muscles of both legs using a device containing 200 LEDs (100 red and 100 infrared). The following variables were assessed: endurance performance (i.e. total time, mean velocity, and velocity in the split distances at the initial 200 m and every 400 m lap) and RPE in the split distances at the initial 200 m and every 400 m lap. Data normality and homogeneity were tested using Shapiro-Wilk's and Levene's tests, respectively. Differences between treatment conditions were assessed using the analysis of variance tests (one- or two-way ANOVA, depending on the comparisons), complemented by the Bonferroni post hoc test. There were significant time effects for the running velocity and RPE in the split distances (p < 0.0001), with no significant treatment-by-time interaction (running velocity, p = 0.59; RPE, p = 0.95). The mean velocity (p = 0.997), total time (p = 0.998), and total mean of the RPE (p = 0.91) were similar between treatment conditions. In conclusion, acute PBMT with LEDs at doses of 300, 900, and 1260 J is not recommended for improving endurance performance and RPE in the 5-km running trial in recreational runners.

Athletes with meditation experience counteract the detrimental effect of mental fatigue on endurance performance and neurocognitive functions.

The current study examined whether meditation experience is associated with changes in endurance performance and inhibitory control-relevant neurocognitive functions caused by mental fatigue. Twenty-four athletes with meditation experience (AME) and twenty-five athletes without meditation experience (AWME) underwent a 30-min incongruent Stroop test in mental fatigue condition (MF) and a 30-min congruent Stroop test in control condition (CON) in a randomised-counterbalanced order. Inhibitory control-relevant neurocognitive functions were assessed using Flanker task and event-related potentials, followed by an endurance task using the Bruce treadmill protocol. Visual analogue scale was used to evaluate perceived mental fatigue (VAS-MF) before (T1), after Stroop test (T2) and after Flanker task (T3), and VAS for motivation (VAS-M) was used to evaluate motivation in Flanker task and endurance task. Results indicated that, compared to the CON, AWME in the MF exhibited overall lower accuracy, smaller incongruent N2 amplitude of the Flanker task (ps < .05), and shorter time to exhaustion (TTE) of the endurance task (p < .001), whereas AME did not exhibited difference in these outcomes between the conditions. Along with athletes in the MF reported lower VAS-M in endurance task. These findings suggest the benefits of meditation experience in mitigating the negative effects of mental fatigue.

Aerobic exercise training-induced alteration of gut microbiota composition affects endurance capacity.

This study aimed to clarify whether aerobic exercise training-induced alterations in the gut microbiota affect physiological adaptation with endurance exercise capacity. In study 1, ICR mice were randomly divided into three groups: vehicle intake + sedentary (V+S), vehicle intake + exercise training (V+Ex) and antibiotic intake + exercise training (AB+Ex). In the exercise training groups, treadmill running was performed for 8 weeks. During the exercise training intervention, the antibiotic-intake group freely drank water containing antibiotics. In study 2, ICR mice were randomly divided into three groups: Sham, transplantation of caecum microbiota from sedentary mice (Sed-CMT) and exercise training mice (Ex-CMT). In study 1, the treadmill running time to exhaustion, an index of maximal aerobic capacity, after aerobic exercise training in the V+Ex group was significantly longer than that in the V+S and AB+Ex groups. Gastrocnemius muscle citrate synthase (CS) activity and PGC-1α protein levels in the V+Ex group were significantly higher than in the V+S and AB+Ex groups. The bacterial Erysipelotrichaceae and Alcaligenaceae families were positively correlated with treadmill running time to exhaustion. In study 2, the treadmill running time to exhaustion after transplantation was significantly higher in the Ex-CMT group than in the Sham and Sed-CMT groups. Furthermore, CS activity and PGC-1α protein levels in the gastrocnemius muscle were significantly higher in the Ex-CMT group than in the Sham and Sed-CMT groups. Thus, gut microbiota altered by aerobic exercise training may be involved in the augmentation of endurance capacity and muscle mitochondrial energy metabolism. KEY POINTS: Aerobic exercise training changes gut microbiota composition, and the Erysipelotrichaceae and Alcaligenaceae families were among the altered gut bacteria. The gut microbiota was associated with endurance performance and metabolic regulator levels in skeletal muscle after aerobic exercise training. Continuous antibiotic treatment attenuated the increase in endurance performance, citrate synthase activity and PGC-1α levels in skeletal muscle induced by aerobic exercise training. Gut microbiota transplantation from exercise-trained mice improved endurance performance and metabolic regulator levels in recipient skeletal muscle, despite the absence of aerobic exercise training.

Hemoglobin mass and performance responses during 4 weeks of normobaric "live high-train low and high".

PURPOSE: To investigate whether 4 weeks of normobaric "live high-train low and high" (LHTLH) causes different hematological, cardiorespiratory, and sea-level performance changes compared to living and training in normoxia during a preparation season. METHODS: Nineteen (13 women, 6 men) cross-country skiers competing at the national or international level completed a 28-day period (∼18 h day-1 ) of LHTLH in normobaric hypoxia of ∼2400 m (LHTLH group) including two 1 h low-intensity training sessions per week in normobaric hypoxia of 2500 m while continuing their normal training program in normoxia. Hemoglobin mass (Hbmass ) was assessed using a carbon monoxide rebreathing method. Time to exhaustion (TTE) and maximal oxygen uptake (VO2max ) were measured using an incremental treadmill test. Measurements were completed at baseline and within 3 days after LHTLH. The control group skiers (CON) (seven women, eight men) performed the same tests while living and training in normoxia with ∼4 weeks between the tests. RESULTS: Hbmass in LHTLH increased 4.2 ± 1.7% from 772 ± 213 g (11.7 ± 1.4 g kg-1 ) to 805 ± 226 g (12.5 ± 1.6 g kg-1 ) (p < 0.001) while it was unchanged in CON (p = 0.21). TTE improved during the study regardless of the group (3.3 ± 3.4% in LHTLH; 4.3 ± 4.8% in CON, p < 0.001). VO2max did not increase in LHTLH (61.2 ± 8.7 mL kg-1 min-1 vs. 62.1 ± 7.6 mL kg-1 min-1 , p = 0.36) while a significant increase was detected in CON (61.3 ± 8.0-64.0 ± 8.1 mL kg-1 min-1 , p < 0.001). CONCLUSIONS: Four-week normobaric LHTLH was beneficial for increasing Hbmass but did not support the short-term development of maximal endurance performance and VO2max when compared to the athletes who lived and trained in normoxia.

Effects of protein-carbohydrate vs. carbohydrate alone supplementation on immune inflammation markers in endurance athletes: a randomized controlled trial.

PURPOSE: The impact of ingesting carbohydrates alone or combined with proteins to support exercise immune adaptation in endurance athletes is scarcely investigated. The present study compares the effect of ingesting a combined protein-carbohydrate supplement vs. a carbohydrate-only supplement post-workout on immune inflammation markers following a 10 week periodized endurance training program in well-trained athletes. METHODS: Twenty-five men completed the study after being randomly assigned to one of the following intervention groups: combined protein-carbohydrate (PRO-CHO n = 12, 31 ± 9 years, [Formula: see text]O2peak 61.0 ± 5.6 ml.kg-1.min-1) or non-protein isoenergetic carbohydrate (CHO, n = 13, 33 ± 8 years, [Formula: see text]O2peak 60.6 ± 6.9 ml.kg-1.min-1). Treatment consisted of ingesting 24 g of assigned supplement, mixed with 250 ml of orange juice, once a day for 10 weeks immediately post-workout (or before breakfast on non-training days). Measurements were conducted pre- and post-intervention on total leukocytes, leukocyte subsets (i.e., neutrophils, eosinophils, basophils, monocytes, and lymphocytes), and platelets. The inflammatory status was assessed by the neutrophil-to-lymphocyte ratio (NLR), the platelet-to-lymphocyte ratio (PLR), and the systemic-immune inflammation index (SII). RESULTS: Post-intervention, significant increases were observed for CHO group only for the three inflammatory markers: NLR (p = 0.050, d = 0.58), PLR (p = 0.041, d = 0.60), and SII (p = 0.004, d = 0.81) but not for PRO-CHO (p > 0.05). CONCLUSION: Ingesting a post-workout protein-carbohydrate combined beverage promoted a more favourable immune status than carbohydrate-only ingestion by attenuating cellular inflammation over a 10 week training period in endurance male athletes. TRIAL REGISTRATION: The study was registered in ClinicalTrials.gov with the following ID: NCT02954367. The study was registered by 3 November 2016.

Can we predict long-duration running power output? A matter of selecting the appropriate predicting trials and empirical model.

When facing a long-distance race, athletes and practitioners could develop an efficient pacing strategy and training paces if an accurate performance estimate of the target distance is achieved. Therefore, this study aims to determine the validity of different empirical models (i.e. critical power [CP], Power law and Peronnet) to predict long-duration power output (i.e. 60 min) when using two or three time trial configurations. In a 5-week training period, fifteen highly trained athletes performed nine-time trials (i.e. 1, 2, 3, 4, 5, 10, 20, 30, and 60 min) in a randomized order. Their power-duration curves were defined through the work-time (CPwork), power-1/time (CP1/time), two-parameter hyperbolic (CP2hyp), three-parameter hyperbolic (CP3hyp) CP models using different two- and three-time trial configurations. The undisclosed proprietary CP models of the Stryd (CPstryd) and Golden Cheetah training software (CPcheetah) were also computed as well as the non-asymptotic Power law and Peronnet models. These were extrapolated to the 60-min power output and compared to the actual performance. The shortest valid configuration (95% confidence interval < 12 W) for CPwork and CP1/time was 3-30 min (Bias: 8.3 [4.9 to 11.7] W), for CPstryd was 10-30 min (Bias: 4.2 [- 1.0 to 9.4] W), for CP2hyp, CP3hyp and CPcheetah was 3-5-30 min (Bias < 5.7 W), for Power law was 1-3-10 min (- 1.0 [- 11.9 to 9.9] W), and for Peronnet was 4-20 min (- 3.0 [- 10.2 to 4.3] W). All the empirical models provided valid estimates when the two or three predicting trial configurations selected attended each model fitting needs.

Modeling lactate threshold in young squad athletes: influence of sex, maximal oxygen uptake, and cost of running.

PURPOSE: This study aimed to investigate: 1. The influence of sex and age on the accuracy of the classical model of endurance performance, including maximal oxygen uptake ([Formula: see text]), its fraction (LT2%), and cost of running (CR), for calculating running speed at lactate threshold 2 (vLT2) in young athletes. 2. The impact of different CR determination methods on the accuracy of the model. 3. The contributions of [Formula: see text], LT2%, and CR to vLT2 in different sexes. METHODS: 45 male and 55 female young squad athletes from different sports (age: 15.4 ± 1.3 years; [Formula: see text]: 51.4 ± 6.8 [Formula: see text]) performed an incremental treadmill test to determine [Formula: see text], LT2%, CR, and vLT2. CR was assessed at a fixed running speed (2.8 [Formula: see text]), at lactate threshold 1 (LT1), and at 80% of [Formula: see text], respectively. RESULTS: Experimentally determined and modeled vLT2 were highly consistent independent of sex and age (ICC [Formula: see text] 0.959). The accuracy of vLT2 modeling was improved by reducing random variation using individualized CR at 80% [Formula: see text] (± 4%) compared to CR at LT1 (± 7%) and at a fixed speed (± 8%). 97% of the total variance of vLT2 was explained by [Formula: see text], LT2%, and CR. While [Formula: see text] and CR showed the highest unique (96.5% and 31.9% of total [Formula: see text], respectively) and common (- 31.6%) contributions to the regression model, LT2% made the smallest contribution (7.5%). CONCLUSION: Our findings indicate: 1. High accuracy of the classical model of endurance performance in calculating vLT2 in young athletes independent of age and sex. 2. The importance of work rate selection in determining CR to accurately predict vLT2. 3. The largest contribution of [Formula: see text] and CR to vLT2, the latter being more important in female athletes than in males, and the least contribution of LT2%.

The effect of tyrosine supplementation on whole-body endurance performance in physically active population: A systematic review and meta-analysis including GRADE qualification.

Although tyrosine supplementation is well recognized to improve cognitive function, its impact on endurance performance is debatable and needs to be clarified further. The purpose of this systematic review and meta-analysis was to evaluate the effects of tyrosine supplementation on whole-body endurance performance in physically active population. The search strategy follow the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA), using four databases (Cochrane Library, Web of Science, Scopus, PsycINFO, and PubMed) until 3 August 2023. The effect of tyrosine (experimental condition) was compared against placebo (control condition). The methodological quality of the included studies was evaluated using the Physiotherapy Evidence Database (PEDro) scale. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE Pro software) System was also used to assess the quality of evidence. A total of 10 interventions from 8 studies were included. The sub-group analysis revealed no significant differences between tyrosine and placebo conditions for time to exhaustion (SMD = 0.02; p = 0.94) and time trial performance (SMD = -0.04; p = 0.85). The level of evidence as qualified with GRADE was moderate. In conclusion, moderate-quality evidence suggests that tyrosine supplementation is ineffective on endurance performance in the physically active population, independently of the endurance task (TTE or ETT).

Prediction of Half-Marathon Power Target using the 9/3-Minute Running Critical Power Test.

Running power output allows for controlling variables that have been previously overlooked by relying solely on speed, such as surface, gradient and weight. The ability to measure this external load variable now enables the analysis of concepts that have predominantly been studied in cycling, such as the Critical Power (CP), in the context of running. This study aims to predict the CP target at which trained athletes run a half-marathon and determine whether races of this distance can serve as a valid alternative to update the CP record. A group of nine trained athletes performed the 9/3-minute Stryd CP test and participated in a half-marathon race in two separate testing sessions conducted in the field. The average power during a half-marathon race is a valid alternative method for determining the CP in trained athletes, as evidenced by the agreement (95% CI: -0.11 to 0.37 W/kg) and trivial systematic bias (0.13 W/kg) between methods. The linear regression model half-marathon power = 0.97 + 0.75·CP (W/kg) showed low standard error of estimate (0.29 W/kg) and significant large association between methods (r = 0.88; p = 0.002). Coaches and athletes should be aware that the CP target for a half-marathon race is 97.3% of the CP determined by the 9/3-minute Stryd CP test.

Sex-based limits to running speed in the human, horse and dog: The role of sexual dimorphisms.

Elite performing men continue to record faster record times in running events compared to women. These sex-based differences in running speed and endurance in humans are expected based on sexual dimorphisms that contribute to differences in the determinants of aerobic performance. Comparatively, the sexual dimorphisms contributing to sex-based differences in elite aerobic performance are not ubiquitous across other species that compete in running events. The purpose of this review is to offer a framework and model for ongoing discussions of the physiological determinants and ultimately limits of physical performance. The records for average running speed of champion athletes were delineated by sex for thoroughbred horses, greyhound dogs, and humans. Male and female performances within each of these species are being optimized by training, nutrition, and financial incentives, and are approaching a performance maximum. For horses and greyhounds breeding also plays a role. Analysis of athletic records shows that there is a sex-related difference of ~10% or more in elite athletic performance for humans; however, the upper limit of performance does not appear to be different between sexes for thoroughbred horses and greyhound dogs. In the context of the nil sex differences in running performance in thoroughbreds and greyhounds, we discuss the physiological role of sexual dimorphisms on sex-specific limits to running performance. We highlight that studies on both human and animal performance in athletic events stimulate critical physiological questions and drive novel research.

The effect of the protective face mask on cardiorespiratory response during aerobic exercise.

The protective face mask (PFM) has been widely used for safety purposes and, after the advent of the COVID-19 pandemic, its use is growing steadily, not only among healthcare personnel but also the general population. While the PFM is important to preserve the wearer from contaminating agents present in the airflow, they are well known to increase the subjective perception of breathing difficulty. Although some studies have demonstrated that PFM use worsens exercise tolerance, several studies state that there is no such limitation with the use of PFM. Moreover, no serious adverse effects during physical exercise have been found in the literature. Physical exercise represents a significant challenge to the human body through a series of integrated changes in function that involve most of its physiologic systems. In this respect, cardiovascular and respiratory systems provide the capacity to sustain physical tasks over extended periods. Within this scenario, both convective oxygen (O2 ) transport (product of arterial O2 content × blood flow) to the working locomotor muscles and O2 diffusive transport from muscle capillaries to mitochondria are of paramount importance to endurance performance. Interestingly, the effects of PFM on cardiorespiratory response during aerobic exercise depends on the type of mask and exercise (i.e., walking, running, or cycling), the ventilatory demands, arterial oxygen levels, maximal oxygen consumption and endurance performance. The purpose of this review is to elucidate the effect of protective face mask-wearing on (1) cardiorespiratory responses during aerobic exercise and (2) endurance performance.

Over 55 years of critical power: Fact or artifact?

This report aims to generate an evidence-based debate of the Critical Power (CP), or its analogous Critical Speed (CS), concept. Race times of top Spanish runners were utilized to calculate CS based on three (1500-m to 5000-m; CS1.5-5km ) and four (1500-m to 10000-m; CS1.5-10km ) distance performances. Male running world records from 1000 to 5000-m (CS1-5km ), 1000 to 10,000-m (CS1-10km ), 1000-m to half marathon (CS1km-half marathon ), and 1000-m to marathon (CS1km-marathon ) distance races were also utilized for CS calculations. CS1.5-5km (19.62 km h-1 ) and CS1.5-10km (18.68 km h-1 ) were different (p < 0.01), but both approached the average race speed of the longest distance chosen in the model, and were remarkably homogeneous among subjects (97% ±1% and 98% ±1%, respectively). Similar results were obtained using the world records. CS values progressively declined, until reaching a CS1km-marathon value of 20.77 km h-1 (10% lower than CS1-5km ). Each CS value approached the average speed of the longest distance chosen in the model (96.4%-99.8%). A power function better fitted the speed-time relationship compared with the standardized hyperbolic function. However, the horizontal asymptote of a power function is zero. This better approaches the classical definition of CP: the power output that can be maintained almost indefinitely without exhaustion. Beyond any sophisticated mathematical calculation, CS corresponds to 95%-99% of the average speed of the longest distance chosen as an exercise trial. CP could be considered a mathematical artifact rather than an important endurance performance marker. In such a case, the consideration of CP as a physiological "gold-standard" should be reevaluated.