Right ventricular remodeling induced by prolonged excessive endurance exercise is mediated by upregulating Wnt/ß-catenin signaling in rats.

BACKGROUND: The aim of this study was to develop an animal model to investigate whether prolonged intensive endurance exercise induces RV remodeling, taking into account the involvement of Wnt/ß-catenin signaling. METHODS: Four-week-old male Wistar rats (100 to 125 g) were assigned to four groups (n = 8/group): 1) sixteen weeks of intensive (36 m/min) exercise (INT), 2) twelve weeks of the intensive exercise followed by four weeks of moderate intensity (18 m/min) exercise (INT + MOD), 3) twelve weeks of the intensive exercise followed by four weeks of detraining (INT + DT), and 4) sedentary rats (SED). The exercise protocols were performed five days a week for one h/day. Echocardiography, real-time PCR, western blotting, and histological staining were performed at the end of week sixteen. RESULTS: INT rats developed concentric hypertrophy without diastolic dysfunction compared to SED (p = 0.006) and INT + DT (p = 0.035). Wnt1, ß-catenin and CyclinD1 proteins in the training groups were significantly higher than SED rats (p < 0.001). Interestingly, INT rats had higher protein levels than INT + DT and INT + MOD (p < 0.001), with higher gene expression compared to SED rats (p < 0.05). There was also a significant increase in collagen deposition in INT rats compared to SED (p = 0.046) and INT + DT (p = 0.034). Furthermore, INT + MOD and INT + DT rats did not show any adverse structural, functional, or histological changes. CONCLUSIONS: Long-term intensive endurance training seems to be associated with increased collagen deposition and wall thickness in the RV through Wnt/ß-catenin signaling (which is concentration dependent), without changes in diastolic function. CLINICAL PERSPECTIVE: Over the past decades, there has been an ongoing debate about whether the structural and functional adaptations of the cardiovascular system in trained endurance athletes are benign physiological responses to training or potentially pathological changes related to disease. While the adaptations of the left heart are well-documented, the remodeling of the right heart remains a subject of discussion. To gain insights into the ability of sustained high-intensity exercise to cause adverse right ventricular (RV) remodeling, we conducted an experimental study in which male rats were trained to run vigorously for 1 h daily over a 16-week period and compared them to a parallel group of sedentary control rats. Our findings revealed that intense long-term exercise induced morphological changes along with fibrosis affecting the RV. These fibrotic changes were a result of the 16-week vigorous exercise training regimen. If these results are confirmed in humans, they suggest that prolonged high-intensity endurance exercise training may lead to adverse cardiac remodeling. Our findings have important potential implications for the assessment of cardiac remodeling in individuals engaged in high-level exercise training.

Polarized running training adapted to versus contrary to the menstrual cycle phases has similar effects on endurance performance and cardiovascular parameters.

PURPOSE: This study compared the effects of polarized running training adapted to the menstrual cycle (MC) phases versus polarized training adapted contrary to the MC on endurance performance and cardiovascular parameters. METHODS: Thirty-three naturally menstruating, moderately trained females (age: 26 ± 4 years; BMI: 22.3 ± 3.2 kg/m2; V ˙ O2max/rel: 40.35 ± 4.61 ml/min/kg) were randomly assigned to a control (CON) and intervention (INT) group. Both groups participated in a load-matched eight-week running training intervention. In the INT, high-intensity sessions were aligned with the mid and late follicular phase, low-intensity sessions with the early and mid-luteal phase, and recovery with the late luteal and early follicular phase. In the CON, high-intensity sessions were matched to the late luteal and early follicular phase, and recovery to the mid and late follicular phase. Endurance performance and cardiovascular parameters were assessed at baseline and after the intervention. RESULTS: Twenty-six females completed the intervention. A repeated measures ANOVA determined no time × group interaction effect for any parameter. A significant time effect was found for maximal oxygen uptake (F(1,12) = 18.753, p = 0.005, ηp2 = 0.630), the velocity at the ventilatory threshold one (F(1,12) = 10.704, p = 0.007, ηp2 = 0.493) and two (F(1,12) = 7.746, p = .018, ηp2 = .413). CONCLUSION: The training intervention improved endurance performance in both groups, with no further benefit observed from the MC-adapted polarized training in a group-based analysis. Replications with an extended intervention period, a larger sample size, and a more reliable MC determination are warranted.

Effect of Cardiovascular Endurance Training on the Exercise Capacity and Endurance in Children With Cerebral Palsy.

BACKGROUND: Cerebral palsy (CP) is non-progressive brain damage that occurs before, during, or shortly after birth. CP is associated with poor physical fitness, which is linked to health problems and the development of secondary illnesses like obesity, cardiovascular disease, and diabetes. Compared to healthy peers without CP, children with CP have considerably lower VO2 peaks, which reduces their performance and aerobic capacity. OBJECTIVE: This study aimed to evaluate changes in exercise capacity and endurance among children with CP, as well as fatigue levels among their parents and caregivers, after participation in cardiovascular endurance training. METHODOLOGY: This study included 16 children aged 7-12 years with CP (Gross Motor Function Classification System levels I, II, or III). Participants completed a 12-week cardiovascular endurance program consisting of 60-minute sessions three times weekly designed to achieve 64-95% of their heart rate maximum,based on the American College of Sports Medicine guidelines. Pre- and post-intervention measurements were recorded for the following: distance covered in a six-minute walk, maximal oxygen consumption (VO2 max) level, Early Activity Scale for Endurance rating, and Patient-Reported Outcomes Measurement Information System (PROMIS) Pediatric Fatigue Scale score and PROMIS Parent Proxy Scale and Fatigue Scale scores.  Result: Upon completing the cardiovascular endurance training, the distance covered during a six-minute walk improved by 20.95 points, resting heart rate by 5.19 points, VO2 max by 0.06 points, Early Activity Scale for Endurance by 4.06 points, PROMIS Pediatric Fatigue Scale by 7.29 points, PROMIS Parent Proxy Scale by 6.81 points, and PROMIS Fatigue Scale by 5.07 points. The maximum heart rate also showed a slight improvement of 0.33 points (p<0.01). CONCLUSION: A structured exercise protocol aimed at improving cardiovascular endurance can benefit children with CP by improving their exercise capacity and endurance, which in turn can help decrease fatigue levels among their parents and caregivers.

Treadmill running and mechanical overloading improved the strength of the plantaris muscle in the dystrophin-desmin double knockout (DKO) mouse.

Limited knowledge exists regarding the chronic effect of muscular exercise on muscle function in a murine model of severe Duchenne muscular dystrophy (DMD). Here we determined the effects of 1 month of voluntary wheel running (WR), 1 month of enforced treadmill running (TR) and 1 month of mechanical overloading resulting from the removal of the synergic muscles (OVL) in mice lacking both dystrophin and desmin (DKO). Additionally, we examined the effect of activin receptor administration (AR). DKO mice, displaying severe muscle weakness, atrophy and greater susceptibility to contraction-induced functional loss, were exercised or treated with AR at 1 month of age and in situ force production of lower leg muscle was measured at the age of 2 months. We found that TR and OVL increased absolute maximal force and the rate of force development of the plantaris muscle in DKO mice. In contrast, those of the tibialis anterior (TA) muscle remained unaffected by TR and WR. Furthermore, the effects of TR and OVL on plantaris muscle function in DKO mice closely resembled those in mdx mice, a less severe murine DMD model. AR also improved absolute maximal force and the rate of force development of the TA muscle in DKO mice. In conclusion, exercise training improved plantaris muscle weakness in severely affected dystrophic mice. Consequently, these preclinical results may contribute to fostering further investigations aimed at assessing the potential benefits of exercise for DMD patients, particularly resistance training involving a low number of intense muscle contractions. KEY POINTS: Very little is known about the effects of exercise training in a murine model of severe Duchenne muscular dystrophy (DMD). One reason is that it is feared that chronic muscular exercise, particularly that involving intense muscle contractions, could exacerbate the disease. In DKO mice lacking both dystrophin and desmin, characterized by severe lower leg muscle weakness, atrophy and fragility in comparison to the less severe DMD mdx model, we found that enforced treadmill running improved absolute maximal force of the plantaris muscle, while that of tibialis anterior muscle remained unaffected by both enforced treadmill and voluntary wheel running. Furthermore, mechanical overloading, a non-physiological model of chronic resistance exercise, reversed plantaris muscle weakness. Consequently, our findings may have the potential to alleviate concerns and pave the way for exploring the prescription of endurance and resistance training as a viable therapeutic approach for the treatment of dystrophic patients. Additionally, such interventions may serve in mitigating the pathophysiological mechanisms induced by physical inactivity.

Textured insoles may improve some gross motor balance measures but not endurance measures in children with motor coordination issues. A randomised controlled feasibility trial.

BACKGROUND: Motor coordination concerns are estimated to affect 5%-6% of school-aged children. Motor coordination concerns have variable impact on children's lives, with gait and balance often affected. Textured insoles have demonstrated positive impact on balance and gait in adults with motor coordination disorders related to disease or the ageing process. The efficacy of textured insoles in children is unknown. Our primary aim was to identify the feasibility of conducting a randomised controlled trial involving children with motor control issues. The secondary aim was to identify the limited efficacy of textured insoles on gross motor assessment balance domains and endurance in children with movement difficulties. METHODS: An assessor-blinded, randomised feasibility study. We advertised for children between the ages of 5-12 years, with an existing diagnosis or developmental coordination disorder or gross motor skill levels assessed as 15th percentile or below on a norm-referenced, reliable and validated scale across two cities within Australia. We randomly allocated children to shoes only or shoes and textured insoles. We collected data across six feasibility domains; demand (recruitment), acceptability (via interview) implementation (adherence), practicality (via interview and adverse events), adaptation (via interview) and limited efficacy testing (6-min walk test and balance domain of Movement ABC-2 at baseline and 4 weeks). RESULTS: There were 15 children randomised into two groups (eight received shoes alone, seven received shoes and textured insoles). We experienced moderate demand, with 46 potential participants. The insoles were acceptable, however, some parents reported footwear fixture issues requiring modification. The 6-min walk test was described as problematic for children, despite all but one child completing. Social factors impacted adherence and footwear wear time in both groups. Families reported appointment locations and parking impacting practicality. Underpowered, non-significant small to moderate effect sizes were observed for different outcome measures. Improvement in balance measures favoured the shoe and insole group, while gait velocity increase favoured the shoe only group. CONCLUSION: Our research indicates that this trial design is feasible with modifications such as recruiting with a larger multi-disciplinary organisation, providing velcro shoe fixtures and using a shorter timed walk test. Furthermore, progressing to a larger well-powered randomised control trial is justified considering our preliminary, albeit underpowered, efficacy findings. TRIAL REGISTRATION: This trial was retrospectively registered with the Australian and New Zealand Clinical Trial Registration: ACTRN12624000160538.

A training goal-oriented categorization model of high-intensity interval training.

There are various categorization models of high-intensity interval training (HIIT) in the literature that need to be more consistent in definition, terminology, and concept completeness. In this review, we present a training goal-oriented categorization model of HIIT, aiming to find the best possible consensus among the various defined types of HIIT. This categorization concludes with six different types of HIIT derived from the literature, based on the interaction of interval duration, interval intensity and interval:recovery ratio. We discuss the science behind the defined types of HIIT and shed light on the possible effects of the various types of HIIT on aerobic, anaerobic, and neuromuscular systems and possible transfer effects into competition performance. We highlight various research gaps, discrepancies in findings and not yet proved know-how based on a lack of randomized controlled training studies, especially in well-trained to elite athlete cohorts. Our HIIT "toolbox" approach is designed to guide goal-oriented training. It is intended to lay the groundwork for future systematic reviews and serves as foundation for meta-analyses.

High-intensity interval training using electrical stimulation ameliorates muscle fatigue in chronic kidney disease-related cachexia by restoring mitochondrial respiratory dysfunction.

Background: Exercise, especially high-intensity interval training (HIIT), can increase mitochondrial respiratory capacity and enhance muscular endurance, but its systemic burden makes it difficult to safely and continuously prescribe for patients with chronic kidney disease (CKD)-related cachexia who are in poor general condition. In this study, we examined whether HIIT using electrical stimulation (ES), which does not require whole-body exercise, improves muscle endurance in the skeletal muscle of 5/6 nephrectomized rats, a widely used animal model for CKD-related cachexia. Methods: Male Wistar rats (10 weeks old) were randomly assigned to a group of sham-operated (Sham) rats and a group of 5/6 nephrectomy (Nx) rats. HIIT was performed on plantar flexor muscles in vivo with supramaximal ES every other day for 4 weeks to assess muscle endurance, myosin heavy-chain isoforms, and mitochondrial respiratory function in Nx rats. A single session was also performed to identify upstream signaling pathways altered by HIIT using ES. Results: In the non-trained plantar flexor muscles from Nx rats, the muscle endurance was significantly lower than that in plantar flexor muscles from Sham rats. The proportion of myosin heavy chain IIa/x, mitochondrial content, mitochondrial respiratory capacity, and formation of mitochondrial respiratory supercomplexes in the plantaris muscle were also significantly decreased in the non-trained plantar flexor muscles from Nx rats than compared to those in plantar flexor muscles from Sham rats. Treatment with HIIT using ES for Nx rats significantly improved these molecular and functional changes to the same degrees as those in Sham rats. Furthermore, a single session of HIIT with ES significantly increased the phosphorylation levels of AMP-activated protein kinase (AMPK) and p38 mitogen-activated protein kinase (MAPK), pathways that are essential for mitochondrial activation signaling by exercise, in the plantar muscles of both Nx and Sham rats. Conclusion: The findings suggest that HIIT using ES ameliorates muscle fatigue in Nx rats via restoration of mitochondrial respiratory dysfunction with activation of AMPK and p38 MAPK signaling. Our ES-based HIIT protocol can be performed without placing a burden on the whole body and be a promising intervention that is implemented even in conditions of reduced general performance status such as CKD-related cachexia.

Tangeretin Enhances Muscle Endurance and Aerobic Metabolism in Mice via Targeting AdipoR1 to Increase Oxidative Myofibers.

Slow oxidative myofibers play an important role in improving muscle endurance performance and maintaining body energy homeostasis. However, the targets and means to regulate slow oxidative myofibers proportion remain unknown. Here, we show that tangeretin (TG), a natural polymethoxylated flavone, significantly activates slow oxidative myofibers-related gene expression and increases type I myofibers proportion, resulting in improved endurance performance and aerobic metabolism in mice. Proteomics, molecular dynamics, cellular thermal shift assay (CETSA) and drug affinity responsive target stability (DARTS) investigations revealed that TG can directly bind to adiponectin receptor 1 (AdipoR1). Using AdipoR1-knockdown C2C12 cells and muscle-specific AdipoR1-knockout mice, we found that the positive effect of TG on regulating slow oxidative myofiber related markers expression is mediated by AdipoR1 and its downstream AMPK/PGC-1α pathway. Together, our data uncover TG as a natural compound that regulates the identity of slow oxidative myofibers via targeting the AdipoR1 signaling pathway. These findings further unveil the new function of TG in increasing the proportion of slow oxidative myofibers and enhancing skeletal muscle performance.

Ultrasound detection of non-atherosclerotic intima-medial abnormalities of lower limbs arteries in amateur endurance runners.

BACKGROUND: Structural changes in the lower limb's arterial wall in amateur endurance runners are a rare incidental finding, represented just by several case reports. AIM: Study the incidence of non-atherosclerotic lower limb artery wall changes in defined group of amateur endurance runners and identify relationship with the training parameters and the relevant biochemical markers. METHODS: Amateur male athletes engaged in endurance running for more than 5 years were enrolled. Tibial and anterior popliteal arteries on each side were examined by ultrasound with focus on non-atherosclerotic structural wall changes: intima-medial border blurring, presence and character of non-atherosclerotic noduli. Subsequently the descriptive and correlation analysis were performed. RESULTS: The study enrolled 20 amateur male endurance runners from Black Swan Triathlon Club Slovakia. The low atherosclerotic risk was represented by normal lipid levels, BMI under 30 kg/m2 and non-smokers in all participants. At least one type of structural artery wall abnormality (noduli or intima-medial border blurring) was present in 19 of 20 participants (95%). The most present was the intima-medial blurring. (80% of participants). The noduli were present in 65% of study group, in almost 40% of these, they were considered as hyperechogenic. All these affections were predominantly in popliteal artery area (65%). The vast majority has bilateral affection. We find a mild correlation between these ultrasound findings and training load represented by annual kilometers and run hours. There was no association between these changes and lipid spectrum or CRP level. CONCLUSION: The subclinical lower limb artery changes, represented by intima-medial border blurring and non-atherosclerotic noduli were present in almost every amateur endurance runner. Despite the underlying mechanism is not understood, the increased training load seems to be one of the responsible factors.

High-level performances following low altitude training and tapering in warm environments in elite racewalkers.

Current guidelines for prolonged altitude exposure suggest altitude levels ranging from 2000 to 2500 m to optimize an increase in total hemoglobin mass (Hbmass). However, natural low altitude locations (<2000 m) remain popular, highlighting the interest to investigate any possible benefit of low altitude camps for endurance athletes. Ten elite racewalkers (4 women and 6 men) underwent a 4-week "live high-train high" (LHTH) camp at an altitude of 1720 m (PIO2 = 121 mmHg; 20.1°C; 67% relative humidity [RH]), followed by a 3-week tapering phase (20 m; PIO2 = 150 mmHg; 28.3°C; 53% RH) in preparation for the World Athletics Championships (WC). Venous blood samples were withdrawn weekly during the entire observation period. In addition, blood volumes were determined weekly by carbon monoxide rebreathing during altitude exposure and 2 weeks after return to sea level. High-level performances were achieved at the WC (five placings among the Top 10 WC races and three all-time career personal bests). A slight but significant increase in absolute (+1.7%, p = 0.03) and relative Hbmass (+2.3%, p = 0.02) was observed after 4-week LHTH. In addition, as usually observed during LHTH protocols, weekly training distance (+28%, p = 0.02) and duration (+30%, p = 0.04) significantly increased during altitude compared to the pre-LHTH period. Therefore, although direct causation cannot be inferred, these results suggest that the combination of increased training load at low altitudes with a subsequent tapering period in a warm environment is a suitable competition-preparation strategy for elite endurance athletes.

Predicting Future Athletic Performance in Young Female Road Cyclists Based on Aerobic Fitness and Hematological Variables.

PURPOSE: This study aimed to determine whether the initial levels of aerobic fitness and hematological variables in young female road cyclists are related to their athletic performance development during their careers. METHODS: Results of graded exercise tests on a cycle ergometer and total hemoglobin mass (tHb-mass) measurements were analyzed in 34 female road cyclists (age 18.6 [1.9] y). Among them, 2 groups were distinguished based on their competitive performance (Union Cycliste Internationale world ranking) over the following 8 years. Areas under the curve in receiver-operating-characteristic curves were calculated as indicators of elite-performance prediction. RESULTS: Initial graded exercise test variables (peak power, peak oxygen uptake, and power at 4 mmol/L blood lactate) were not significantly different in elite (n = 13) versus nonelite (n = 21) riders. In contrast, elite riders had higher tHb-mass expressed either in absolute measures (664 [75] vs 596 [59] g, P = .006) or normalized to body mass (11.2 [0.8] vs 10.3 [0.7] g/kg, P = .001) and fat-free mass (14.4 [0.9] vs 13.1 [0.9] g/kg, P < .001). Absolute and relative erythrocyte volumes were significantly higher in elite subjects (P ranged from < .001 to .006). Of all the variables analyzed, the relative tHb-mass had the highest predictive ability to reach the elite level (area under the curve ranged from .82 to .85). CONCLUSION: Measurement of tHb-mass can be a helpful tool in talent detection to identify young female road cyclists with the potential to reach the elite level in the future.

Importance of shoulder girdle and finger flexor muscle endurance in advanced male climbers.

Aim: This study aimed to: (a) assess the relationships between climbing performance and finger and shoulder girdle muscle endurance; and (b) provide evidence on the validity of the specialized exercise tests used for the purpose. Materials and methods: 28 male sport climbers (climbing ability 23 ± 2.43 IRCRA scale) performed four tests muscle failure, including two-finger hang tests (using 2.5 and 4 cm holds) and two variants of pull-up exercises (classical pull-ups and a combination of dynamic and isometric actions - the so-called Edlinger). Climbing performance and test results were subjected to correlation, taxonomic and regression analysis. Results: The correlations between the results from all tests and climbing performance were notably strong ( r between 0.54 and 0.61) and statistically significant ( p < 0.05 ). The taxonomic analysis indicated that the two variants of each test type reflect two different latent variables 2.5 cm and 4 cm finger hang durations were highly correlated ( r = 0.76 , p < 0.01 ). A similar correlation was found between the results from the pull-up tests ( r = 0.72 , p < 0.01 ). Thus, the finger hang and pull-up test results were determined to a high extent (43% and 49%, respectively) by factors that cannot be assessed when only one test of each type is used. The regression model of the two-finger tests allowed individual endurance profiles to be assessed. Conclusions: The muscular endurance of the elbow flexors and shoulder girdle muscles predicts climbing performance within the specific sport level studied to a comparable degree as finger flexor endurance.The use of two variants of a test intended to assess one physical ability provided important details on a climber's fitness.

Influence of the CYP1A2 c.-163 A > C polymorphism in the effect of caffeine on fat oxidation during exercise: a pilot randomized, double-blind, crossover, placebo-controlled trial.

PURPOSE: The aim of this study was to determine the influence of the CYP1A2 c.-163 A > C (rs762551) polymorphism on the effect of oral caffeine intake on fat oxidation during exercise. METHODS: Using a pilot randomized, double-blind, crossover, placebo-controlled trial, 32 young and healthy individuals (women = 14, men = 18) performed an incremental test on a cycle ergometer with 3-min stages at workloads from 30 to 70% of maximal oxygen uptake (VO2max). Participants performed this test after the ingestion of (a) placebo; (b) 3 mg/kg of caffeine; (c) 6 mg/kg of caffeine. Fat oxidation rate during exercise was measured by indirect calorimetry. The influence of the CYP1A2 c.-163 A > C polymorphism in the effect of caffeine on fat oxidation rates during exercise was established with a three-way ANOVA (substance × genotype × intensity). RESULTS: Eight participants were genotyped as AA, 18 participants were CA heterozygotes, and 6 participants were CC. There was a main effect of substance (F = 3.348, p = 0.050) on fat oxidation rates during exercise with no genotype effect (F = 0.158, p = 0.959). The post hoc analysis revealed that, in comparison to the placebo, 3 and 6 mg/kg of caffeine increased fat oxidation at 40-50% VO2max in AA (all p < 0.050) and 50-60% VO2max in CA and CC participants (all p < 0.050). CONCLUSION: Oral intake of 3 and 6 mg/kg of caffeine increased fat oxidation rate during aerobic exercise in individuals with AA, CA and CC genotypes. This suggests that the effect of caffeine to enhance fat oxidation during exercise is not influenced by the CYP1A2 c.-163 A > C polymorphism. TRIAL REGISTRATION: The study was registered on clinicaltrials.gov with ID: NCT05975489.

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.

A multi-epigenomic map of endurance exercise training.

The Molecular Transducers of Physical Activity Consortium (MoTrPAC) aims to comprehensively map molecular alterations in response to acute exercise and chronic training. In one of a recent series of papers from MoTrPAC, Nair et al. provide the first multi-epigenomic and transcriptomic integration across eight tissues in both sexes following adaptation to endurance exercise training (EET).

Swimming Performance in Elite Triathletes: Comparison Between Open Water and Pool Conditions.

This study aimed to compare performance, kinematic, and physiological variables between open water and pool swimming conditions in elite triathletes and to examine the associations between conditions on these variables. Fourteen elite triathletes (10 males and 4 females [23.4 ± 3.8 years]) performed two 1500-m swimming tests in open water and in a 25-m pool. Swimming speed, stroke rate (SR), length (SL) and index (SI), heart rate (HR), blood lactate concentrations [La-], and end-exercise oxygen uptake (EEV̇O2) were assessed in both conditions. Lower SL and SI and higher SR were obtained in open water compared with pool swimming (p < 0.05). Moreover, kinematic variables changed as a function of distance in both conditions (p < 0.05). No differences were found in the main physiological variables (HR, [La-], and EEV̇O2) between conditions. Respiratory exchange ratio presented lower values in open water than in pool conditions (p < 0.05), while time constant was higher in open water (p = 0.032). The fastest triathletes in open water obtained the best performance in the pool (r = 0.958; p < 0.001). All kinematic variables, HR and peak [La-] presented positive associations between conditions (r > 0.6; p < 0.05). Despite physiological invariance, triathletes and coaches should monitor specific open water training to adapt their swimming technique to the competitive environment.

Association between aerobic performance and physiological responses in Yo-Yo intermittent recovery test level 2, and the futsal-specific intermittent endurance test in trained futsal players.

OBJECTIVES: This prospective cross-sectional study aimed to delineate associations between the performance and physiological responses to the Bruce test with two field tests, the futsal intermittent endurance test (FIET) and the Yo-Yo intermittent recovery test level-2 (YYIR2) in elite male futsal players, in order to endorse one of field test to futsal coaches. METHODS: Fifteen elite futsal players (age 20 ± 3 years) have been participated in this study. Main outcome measurements included aerobic power, heart rate, blood lactate, ventilation, VO2, VCO2, VE-VO2, and VE-VCO2 indicators during FIET, YYIR2, and the Bruce test with carrying out a portable gas analyzer. RESULTS: The Bruce test is significantly correlated with FIET and YYIR2 with respect to key outcome measures, including performance (r>0.59), aerobic power (r>0.69), heart rate (r>0.80), and blood lactate levels (r>0.60). The two field tests, FIET and YYIR2, were found to exhibit strong to perfect interrelationships. When examining the indicators such as VE, VO2, VCO2, VE-VO2, and VE-VCO2, moderate to strong correlations were identified across all three testing methods. However, the relationship between the Bruce test and YYIR2 was particularly noteworthy in terms of respiratory exchange ratio (RER) and metabolic equivalent of task (METS), showing a significant correlation. CONCLUSIONS: The YYIR2 and FIET appear to be valid practical field tests for measuring aerobic fitness and performance in competitive male futsal players.

Prevalence of reducing carbohydrate intake and fasted training in elite endurance athletes and association with bone injury.

There are conflicting reports both within the lay media and scientific literature regarding the use and benefit of dietary practices that aim to reduce CHO intake in endurance athletes. This study aimed to determine the prevalence of intentional reduction of CHO intake and fasted training in elite endurance-based athletes using a semi-quantitative questionnaire. Bone is a nutritionally modulated tissue; therefore, this study also aimed to explore if these dietary practices are potentially associated with bone injury incidence. The reported reduction of CHO intake was prevalent (28%) with the primary motivation being maintenance or manipulation of body composition. However, discrepancies in athletes' awareness of CHO intake were identified providing a potential avenue of intervention especially within applied practice. The use of fasted training was more prevalent (38%) with athletes using this practice for both body composition manipulation and promoting a desired adaptive response. Forty-four per cent of participants had suffered a radiographically confirmed bone injury at some point in their career. There was no association between reduction in CHO intake and bone injury incidence; however, the incidence of bone injury was 1.61 times higher in those who currently use fasted training compared to those who have never used it or who have used it in the past. Although a direct causal link between these dietary practices and the incidence of bone injury cannot be drawn, it provides robust justification for future investigations of the potential mechanisms that could explain this finding.