Endurance Performance In Athletes Research Articles

Cardiac remodeling after six weeks of high-intensity interval training to exhaustion in endurance-trained men.

High-intensity interval training (HIIT) improves physical performance of endurance athletes, although studies examining its cardiovascular effects are sparse. We evaluated the impact of HIIT on blood pressure, heart rate, and cardiac cavities' size and function in endurance-trained adults. Seventeen endurance-trained men underwent 24-h ambulatory blood pressure monitoring and Doppler echocardiography at baseline and after 6 wk of HIIT. Participants were divided into 2 groups [85% maximal aerobic power (HIIT85), n = 8 and 115% maximal aerobic power (HIIT115), n = 9] to compare the impact of different HIIT intensities. Ambulatory blood pressure monitoring and cardiac chambers' size and function were similar between groups at baseline. HIIT reduced heart rate (55 ± 8 vs. 51 ± 7 beats/min; P = 0.003), systolic blood pressure (121 ± 11 vs. 118 ± 9 mmHg; P = 0.01), mean arterial pressure (90 ± 8 vs. 89 ± 6 mmHg; P = 0.03), and pulse pressure (52 ± 6 vs. 49 ± 5 mmHg; P = 0.01) irrespective of training intensity. Left atrium volumes increased after HIIT (maximal: 50 ± 14 vs. 54 ± 14 mL; P = 0.02; minimal: 15 ± 5 vs. 20 ± 8 mL; P = 0.01) in both groups. Right ventricle global longitudinal strain lowered after training in the HIIT85 group only (20 ± 4 vs. 17 ± 3%, P = 0.04). In endurance-trained men, 6 wk of HIIT reduced systolic blood pressure and mean arterial pressure and increased left atrium volumes irrespective of training intensity, whereas submaximal HIIT deteriorated right ventricle systolic function.NEW & NOTEWORTHY The novel findings of this study are that 6 wk of high-intensity interval training increases left atrial volumes irrespective of training intensity (85 or 115% maximal aerobic power), whereas the submaximal training decreases right ventricular systolic function in endurance-trained men. These results may help identify the exercise threshold for potential toxicity of intense exercise training for at-risk individuals and ideal exercise training regimens conferring optimal cardiovascular protection and adapted endurance training for athletes.

A New Method to Improve Running Economy and Maximal Aerobic Power in Athletes: Endurance Training With Periodic Carbon Monoxide Inhalation

BackgroundAltitude training stimulates erythropoietin hormone (EPO) release and increases blood hemoglobin (Hb) mass, which may result in improved oxygen (O2) transport capacity. It was hypothesized in the present study that periodic inhalation of carbon monoxide (CO) might elicit similar physiological adaptations compared to altitude training.MethodsTwelve male college student athletes, who were well-trained soccer players, participated. They performed a 4-week treadmill-training program, five times a week. Participants were randomly assigned into an experimental group with inhaling CO (INCO) (1 mL/kg body weight for 2 min) in O2 (4 L) before all training sessions and a control group without inhaling CO (NOCO). CO and EPO concentrations in venous blood were first measured acutely at the 1st, 2nd, 4th, 6th, and 8th hour after INCO, and total hemoglobin mass (tHb), running economy and VO2max were measured before and after the 4 weeks training intervention.ResultsHbCO% increased from 0.7 to 4.4% (P < 0.05) after 1 h of CO inhalation and EPO increased from 1.9 to 2.7 mIU/mL after 4 h post CO inhalation (P < 0.05) acutely before the intervention. After the training, the tHb and VO2max in the INCO group increased significantly by 3.7 and 2.7%, respectively, while no significant differences were observed in the NOCO condition. O2 uptake at given submaximal speeds declined by approximately 4% in the INCO group.ConclusionAcutely, EPO increased sharply post CO inhalation, peaking at 4 h post inhalation. 4-weeks of training with CO inhalation before exercise sessions improved tHb and VO2max as well as running economy, suggesting that moderate CO inhalation could be a new method to improve the endurance performance in athletes.

Putative Role of Respiratory Muscle Training to Improve Endurance Performance in Hypoxia: A Review.

Respiratory/inspiratory muscle training (RMT/IMT) has been proposed to improve the endurance performance of athletes in normoxia. In recent years, due to the increased use of hypoxic training method among athletes, the RMT applicability has also been tested as a method to minimize adverse effects since hyperventilation may cause respiratory muscle fatigue during prolonged exercise in hypoxia. We performed a review in order to determine factors potentially affecting the change in endurance performance in hypoxia after RMT in healthy subjects. A comprehensive search was done in the electronic databases MEDLINE and Google Scholar including keywords: “RMT/IMT,” and/or “endurance performance,” and/or “altitude” and/or “hypoxia.” Seven appropriate studies were found until April 2018. Analysis of the studies showed that two RMT methods were used in the protocols: respiratory muscle endurance (RME) (isocapnic hyperpnea: commonly 10–30′, 3–5 d/week) in three of the seven studies, and respiratory muscle strength (RMS) (Powerbreathe device: commonly 2 × 30 reps at 50% MIP (maximal inspiratory pressure), 5–7 d/week) in the remaining four studies. The duration of the protocols ranged from 4 to 8 weeks, and it was found in synthesis that during exercise in hypoxia, RMT promoted (1) reduced respiratory muscle fatigue, (2) delayed respiratory muscle metaboreflex activation, (3) better maintenance of SaO2 and blood flow to locomotor muscles. In general, no increases of maximal oxygen uptake (VO2max) were described. Ventilatory function improvements (maximal inspiratory pressure) achieved by using RMT fostered the capacity to adapt to hypoxia and minimized the impact of respiratory stress during the acclimatization stage in comparison with placebo/sham. In conclusion, RMT was found to elicit general positive effects mainly on respiratory efficiency and breathing patterns, lower dyspneic perceptions and improved physical performance in conditions of hypoxia. Thus, this method is recommended to be used as a pre-exposure tool for strengthening respiratory muscles and minimizing the adverse effects caused by hypoxia related hyperventilation. Future studies will assess these effects in elite athletes.

Preparation for Endurance Competitions at Altitude: Physiological, Psychological, Dietary and Coaching Aspects. A Narrative Review.

It was the Summer Olympic Games 1968 held in Mexico City (2,300 m) that required scientists and coaches to cope with the expected decline of performance in endurance athletes and to establish optimal preparation programs for competing at altitude. From that period until now many different recommendations for altitude acclimatization in advance of an altitude competition were proposed, ranging from several hours to several weeks. Those recommendations are mostly based on the separate consideration of the physiology of acclimatization, psychological issues, performance changes, logistical or individual aspects, but there is no review considering all these aspects in their entirety. Therefore, the present work primarily focusses on the period of altitude sojourn prior to the competition at altitude based on physiological and psychological aspects complemented by nutritional and sports practical considerations.

Effects of ischemic preconditioning on economy, VO2 kinetics and cycling performance in endurance athletes.

The aim of this study was to determine the effect of ischemic preconditioning (IPC) on several measures of aerobic function and 4-km cycling time-trial performance. An acute cross-over design was adopted involving eight well-trained cyclists (age 27.0 ± 7.0years) who completed incremental and square-wave exercise tests for determination of peak O2 uptake (VO2peak), ventilatory threshold (VT) and moderate- and heavy-intensity domain VO2 kinetics, as well as 4-km time trials. All were preceded by IPC, or sham-IPC, involving repeated bouts of thigh blood flow occlusion, interspersed with reperfusion. There was no significant difference between IPC and sham-IPC with respect to VO2peak (4.4 ± 0.6Lmin-1 vs 4.4 ± 0.5Lmin-1, effect size - 0.01 ± 0.09), VT (3.4 ± 0.6Lmin-1 vs 3.5 ± 0.5Lmin-1, effect size 0.07 ± 0.28), cycling economy (4.9 ± 4.9%, ES 0.24 ± - 0.24, P > 0.05) or any moderate-domain VO2 kinetic parameter. During heavy-intensity exercise, a reduced end-exercise VO2, slow component amplitude and overall gain was observed following IPC compared to sham-IPC. Though not statistically significant, there was a possibly beneficial effect of IPC on 4-km time-trial mean power output (2.2 ± 2.0%; effect size: 0.18 ± 0.15, P > 0.05). The observed reduction in VO2 slow component and tendency for improved economy and 4-km time-trial performance, albeit small, suggests that acute IPC shows some potential as a performance-enhancing priming strategy for well-trained cyclists prior to high-intensity exercise.

Dietary sugars, exercise and hepatic carbohydrate metabolism.

The present paper reviews the physiological responses of human liver carbohydrate metabolism to physical activity and ingestion of dietary sugars. The liver represents a central link in human carbohydrate metabolism and a mechanistic crux point for the effects of dietary sugars on athletic performance and metabolic health. As a corollary, knowledge regarding physiological responses to sugar ingestion has potential application to either improve endurance performance in athletes, or target metabolic diseases in people who are overweight, obese and/or sedentary. For example, exercise increases whole-body glycogen utilisation, and the breakdown of liver glycogen to maintain blood glucose concentrations becomes increasingly important as exercise intensity increases. Accordingly, prolonged exercise at moderate-to-high exercise intensity results in depletion of liver glycogen stores unless carbohydrate is ingested during exercise. The exercise-induced glycogen deficit can increase insulin sensitivity and blood glucose control, and may result in less hepatic lipid synthesis. Therefore, the induction and maintenance of a glycogen deficit with exercise could be a specific target to improve metabolic health and could be achieved by carbohydrate (sugar) restriction before, during and/or after exercise. Conversely, for athletes, maintaining and restoring these glycogen stores is a priority when competing in events requiring repeated exertion with limited recovery. With this in mind, evidence consistently demonstrates that fructose-containing sugars accelerate post-exercise liver glycogen repletion and could reduce recovery time by as much as half that seen with ingestion of glucose (polymers)-only. Therefore, athletes aiming for rapid recovery in multi-stage events should consider ingesting fructose-containing sugars to accelerate recovery.

PO-049 The Effects of Altitude Training on Erythropoietic Response and Hematological Variables in elite endurance athletes

Objective To increase the capacity of blood oxygen-carrying of the endurance performance in athletes is the goal of altitude training. The key factor in the achievement of enhanced hematological variables is the stimulation in the hypoxia condition. Reticulocyte celles is the earliest red blood cells released to the bloods, it to be matured about 4days in the marrow. There are lots of research in the clinic tested reticulocyte can be monitor the change of the bone marrow hematopoietic system. The purpose of this study was to find out the effect of altitude training on reticulocyte indices of elite endurance athletes, further to analyzes the kinetics of erythropoiesis and hematological variables during and after altitude training.&#x0D; Methods The main content of high altitude training are as following: 1~2weeks before the plateau, the main content of training was special aerobic endurance training and special strength endurance training; 1~5days after plateau, the main content of training was Low intensity, relaxation of the adaptive training; 5~15day after plateau, the main content of training was Intensive training phase, the main content of training was aerobic endurance and greater intensity of the special training; 16~20 days after the plateau, adjustment training 21~25days after the plateau, the main content of training was same to the training plan of 5~15day after plateau; 2~3days after return to the sea level, adjustment training; 1~2days after return to the sea level, the mainly training content was rhythm and strength training; 2 weeks after return to the sea level, the mainly content of training was normal training, the intensity of training was greater than the intensity in the sea level.&#x0D; At this stage, we tested the changes of the reticulocyte indices before \after half past three weeks altitude（2366m,DuoBa,QingHai）training, to provided the basis for the develop research the influence of the bone marrow hematopoietic system. Blood parameters were collected two days before altitude training\two days after off altitude\ two weeks after altitude. All the data measured from venous blood samples (1.5~2ml) collected via venipuncture from athletes in a supine position. All the samples were tested using ADVIA120. Data were analyzed by spss17.0 software.&#x0D; Results MCVr/RDWr were significantly increased after altitude training, P＜0.05; CHCMr and RDWr significantly decreased after altitude training, P＜0.05; CHCMr were changed more significantly between before and after , P＜0.01; the reason why retici# was decreased were analyzed that when the athletes training in the hypoxia condition, lack of oxygen and the mechanical injury of friction resulting in a new generation of reticulocyte number was less than the number of destruction. Hb\#RETIC\RDW were changed significantly, P＜0.05; but there was no significant changed find in RBC/HCT. After two weeks off altitude, MCVr、CHCMr、#RETIC、%RETIC all had significantly changed，P＜0.05;and #RETIC，P＜0.01；Hb is significantly increased controlled to the indices which tested before the athletes went to the altitude. It indicated altitude training can stimulated the bone marrow hematopoietic system to released more reticulocyte cells.RBC and HCT were decreased in our study ,but they were not showed any significantly changed, to analyzed that we found it was relatively large individual differences, which mean the athletes had the different reaction when they training in the plateau and after they back to the sea level; RDW was increased ,but it was not showed the significantly changes too. IRF was increased, but #RETIC\%RETIC\RBCwere decreased after back to the sea level, it showed that the #reticulocyte was not increased, it means that the consumption of the RBC was faster than the number of the erythropoiesis. The indices(CHr、MCVr、CHCMr) which correlated with the Hb contents was increased significantly, it indicated the stimulate of the hypoxia condition can enhance the synthetic of hemoglobin content, but the effect was not occur immediately, it will occurred after 2~3weeks after the athletes back to the sea level.&#x0D; Conclusions Because the test groups were top-level middle-long distance race athletes, they were adapt the training stimulate, so it can not make the reticulocyte indices changed solely, but in the plateau where lack of the oxygen, it will be result the bone marrow hematopoietic system to released more reticulocyte cells to satisfied the needs of the oxygen; the indices which be mutually related with Hb and #reticulocyte both showed the good effece, it indicated that there had certain effect of altitude training on erythropoiesis, but these changes did not showed immediately, it needs 2~3 weeks to occur after returning to sea level.

Single Dose Administration of Taheebo Polyphenol Enhances Endurance Capacity in Mice

Endurance capacity is important for maintenance of quality of life as well as performance of endurance athletes. In order to improve endurance, intake of nutritional supplements as well as exercise training is also important. Indeed, polyphenolic extracts from plants are known to improve endurance capacity via increase of fatty acid utilization, mitochondrial biogenesis or inhibition of oxidative stress. Taheebo, the extract obtained from inner bark of Tabebuia avellanedae has been reported to have beneficial effects for treatment of inflammation, oxidative stress and obesity. Here, we investigated the effects and mechanisms of polyphenol fraction of taheebo (taheebo polyphenol; TP) on endurance capacity of mice. Single dose administration of TP significantly increased running time until exhaustion. Acute TP administration increased blood glucose and muscle glycogen levels (p < 0.05) through alteration on expression level of genes involved with glycogen metabolism and gluconeogenesis. Furthermore, TP administration decreased exercise-induced increase of protein carbonyls in skeletal muscle. These results suggest that TP administration improve endurance capacity via up-regulation of skeletal muscle glycogen levels and maintenance of blood glucose by acceleration of gluconeogenesis as well as inhibition of exercise-induced oxidative stress. Single administration of TP also increased phosphorylation of AMP-activated protein kinase (AMPK) and gene expression level of sirtuin 1 (SIRT1) but did not change the marker of mitochondrial biogenesis.

Relationship between total hemoglobin mass and competitive performance in endurance athletes.

Determine the relationships between total hemoglobin mass (tHb-mass), h emoglobin (Hb), hematocrit (Hct) and competitive performance. The team of 35 elite endurance athletes (biathlon men [BM, N.=12] & women [BW, N.=10], long track speed-skating men [SM, N.=7] and women [SW, N.=6]) were examined before participate in seven different competitions (C1 through C7) during the 2012-2013 and 2013-2014 seasons. Total hemoglobin mass measurement and biochemical analysis were performed using carbon monoxide rebreathing technique 24 hours before the competition. In BM correlations were found between results of two 10-km sprint competitions and tHb-mass between C1 and C2 (r=-0.94 and r=-0.87). Correlations were also found between tHb-mass and performance in C3 individual races for BM (16.765 km, r=-0.88; and 10-km sprint, r=0.80) and BW (7.2 km, r=-0.79; and 10-km sprint, r=-0.81). In SM, a correlation was found between tHb-mass and performance (r=-0.83) in C5. In SM and SW correlations were seen between tHb-mass and performance (SM, 5,000-m; r=-0.80; SW, 3,000-m; r=-0.77) in C6. No correlation was found between performance and Hb or Hct in any group. The demonstration of significant and direct correlation between tHb-mass and competitive performance highlights the importance of tHb-mass in this context and may be relevant for coaches providing one more piece of information for training.

Caffeine, CYP1A2 Genotype, and Endurance Performance in Athletes.

Many studies have examined the effect of caffeine on exercise performance, but findings have not always been consistent. The objective of this study was to determine whether variation in the CYP1A2 gene, which affects caffeine metabolism, modifies the ergogenic effects of caffeine in a 10-km cycling time trial. Competitive male athletes (n = 101; age = 25 ± 4 yr) completed the time trial under three conditions: 0, 2, or 4 mg of caffeine per kilogram body mass, using a split-plot randomized, double-blinded, placebo-controlled design. DNA was isolated from saliva and genotyped for the -163A > C polymorphism in the CYP1A2 gene (rs762551). Overall, 4 mg·kg caffeine decreased cycling time by 3% (mean ± SEM) versus placebo (17.6 ± 0.1 vs 18.1 ± 0.1 min, P = 0.01). However, a significant (P <0.0001) caffeine-gene interaction was observed. Among those with the AA genotype, cycling time decreased by 4.8% at 2 mg·kg (17.0 ± 0.3 vs 17.8 ± 0.4 min, P = 0.0005) and by 6.8% at 4 mg·kg (16.6 ± 0.3 vs 17.8 ± 0.4 min, P < 0.0001). In those with the CC genotype, 4 mg·kg increased cycling time by 13.7% versus placebo (20.8 ± 0.8 vs 18.3 ± 0.5 min, P = 0.04). No effects were observed among those with the AC genotype. Our findings show that both 2 and 4 mg·kg caffeine improve 10-km cycling time, but only in those with the AA genotype. Caffeine had no effect in those with the AC genotype and diminished performance at 4 mg·kg in those with the CC genotype. CYP1A2 genotype should be considered when deciding whether an athlete should use caffeine for enhancing endurance performance.

INFLUENCE OF MORPHOLOGICAL CHARACTERISTICS ON RUNNING PERFORMANCE OF ENDURANCE ATHLETES

Running is a popular form of physical activity and can be carried out through several different distances. Morphological characteristics, such as skin fold thickness, limb girth and length, body weight and body fat percentage have an impact on endurance running. The objective of this systematic review study is to collect and analyze studies about the influence of morphological characteristics on running performance of endurance athletes. Based on an analysis of electronic databases and the inclusion criteria set, 20 studies were included in the analysis. The length of the extremities and the sum of the skin folds thickness have the highest statistical significance as the predictor. The results of the analyzed studies indicate that slim limbs, longer legs, lower total skin fold thickness and lower body fat percentage are some of the characteristics that can be good predictors for competitive success and a model to be tended during the preparation period of male and female endurance runners.

Energy Availability, Macronutrient Intake, and Nutritional Supplementation for Improving Exercise Performance in Endurance Athletes.

Endurance athletes use nutritional guidelines and supplements to improve exercise performance and recovery. However, use is not always based on scientific evidence of improved performance, which type of athlete would benefit most, or the optimal dose and timing of a particular supplement. Health professionals that give advice to athletes need to target their recommendations on the energy systems and muscle fiber types used for the athlete's sporting event, the goal of the training block, the time of the competitive season, and the characteristics and food preferences of the individual athlete. This review aims to summarize the most current research findings on the optimal calorie, carbohydrate, and protein intake for athlete health, performance, and recovery. We also summarized new findings on fluid intake and the optimal dose and timing of beetroot and caffeine supplementation on time trial performance in endurance athletes.

The Effects of Altitude Training on Erythropoietic Response and Hematological Variables in Adult Athletes: A Narrative Review.

Background: One of the goals of altitude training is to increase blood oxygen-carrying capacity in order to improve sea-level endurance performance in athletes. The elevated erythropoietin (EPO) production in hypoxia is a key factor in the achievement of enhanced hematological variables. The level of the EPO increase and acceleration of erythropoiesis depend on the duration of exposure and degree of hypoxia. Furthermore, many other factors may affect the hematological response to altitude training.Aim: The purpose of this narrative review was to: (1) analyze the kinetics of EPO and hematological variables during and after altitude training; (2) summarize the current state of knowledge about the possible causes of individual or cohort differences in EPO and hematological response to altitude training; (3) formulate practical guidelines for athletes to improve the efficiency of altitude training.Methods: A narrative review was performed following an electronic search of the databases PubMed/MEDLINE and SPORTDiscus via EBSCO for all English-language articles published between 1997 and 2017.Results: Complete unification of results from studies on EPO kinetics was difficult due to different time and frequency of blood sampling by different researchers during and after altitude training, but the data presented in the reviewed literature allowed us to detect certain trends. The results of the reviewed studies were divergent and indicated either increase or no change of hematological variables following altitude training. Factors that may affect the hematological response to altitude training include hypoxic dose, training content, training background of athletes, and/or individual variability of EPO production.Conclusions: Despite the potential benefits arising from altitude training, its effectiveness in improving hematological variables is still debatable. Further research and better understanding of factors influencing the response to altitude, as well as factors affecting the suitable measurement and interpretation of study results, are needed.

Responsiveness of the Countermovement Jump and Handgrip Strength to an Incremental Running Test in Endurance Athletes: Influence of Sex.

The present study analyzed the acute effects of an incremental running test on countermovement jump (CMJ) and handgrip strength performance in endurance athletes, considering the effect of post-exercise recovery time and sex. Thirty-three recreationally trained long-distance runners, 20 men and 13 women, participated voluntarily in this study. The participants performed the Léger test, moreover, the CMJ and handgrip strength tests were carried out before and after the running test and during different stages of recovery (at the 1st min of recovery (posttest1), 5th min of recovery (posttest2), and 10th min of recovery (posttest3)). Two-way analysis of variance revealed a significant improvement in the CMJ (pre-posttest1, p = 0.001) and handgrip strength (pre-posttest2, p = 0.017) during recovery time. The Pearson’s Chi-2 test showed no significant relationship (p ≥ 0.05) between sex and post-activation potentiation (PAP). A linear regression analysis pointed to heart rate recovery as a predictive factor of CMJ improvement (PAP). In conclusion, despite significant fatigue reached during the Léger test, the long-distance runners did not experience an impaired CMJ and handgrip strength performance, either men or women, achieving an improvement (PAP) in posttest conditions. The results obtained showed no significant relationship between sex and PAP. Moreover, significant effect of recovery after running at high intensity on CMJ performance and handgrip strength was found. Finally, the data suggest that PAP condition can be predicted by heart rate recovery in endurance runners.

Facile chemical routes to mesoporous silver substrates for SERS analysis

Mesoporous silver nanoparticles were easily synthesized through the bulk reduction of crystalline silver(I) oxide and used for the preparation of highly porous surface-enhanced Raman scattering (SERS)-active substrates. An analogous procedure was successfully performed for the production of mesoporous silver films by chemical reduction of oxidized silver films. The sponge-like silver blocks with high surface area and the in-situ-prepared mesoporous silver films are efficient as both analyte adsorbents and Raman signal enhancement mediators. The efficiency of silver reduction was characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The developed substrates were applied for SERS detection of rhodamine 6G (enhancement factor of about 1–5 × 105) and an anti-ischemic mildronate drug (meldonium; enhancement factor of ≈102) that is known for its ability to increase the endurance performance of athletes.

Evaluation of nutrition knowledge of professional football players

Background: Adequate knowledge of nutrition is believed to influence the performance of endurance athletes. Objectives: To assess the level of nutrition knowledge among football players in Benghazi. Subjects and Methods: Following ethical approval, a cross-sectional study was conducted involving 101 football (soccer) players (25 ± 5 years of age) from seven clubs of the first and second divisions. The height (cm) and weight (kg) were recorded for each player. A questionnaire composed of three sections was filled out by each participant. It included questions concerning personal data, general nutrition, and specific knowledge concerning the appropriate foods to consume before, during, and after exercise. Results: The mean body mass index was 24 ± 2 kg/m2. Fifty-seven percent of the participants were below the university level of formal education. Furthermore, 75% reported that they never received any formal education related specifically to nutrition. In addition, 70% had no knowledge of the concept of the food pyramid, and only 18% of the players communicated with dieticians either during season or off-season. Only 22% answered correctly the questions about which foods are appropriate to consume before and after exercise. Noticeably, 81% of the participants did not correctly identify the contents of the nutrient to be consumed during exercise. Conclusions: The study revealed an alarming lack of nutrition knowledge among professional football players in Benghazi. The results highlight the need to establish specific programs for nutrition education for the players to enhance their knowledge in this critical area and positively influence their dietary habits and ultimately improve their physical performance. It is also important to emphasize the role of qualified dieticians in athletic clubs.

Limiares de transição fisiológica em corredores de montanhas: uma revisão sistemática

The identification of physiological transition thresholds (TT) is commonly used for prescribing and evaluating the performance of endurance athletes; however, the methods need further investigation in mountain runner athletes. The aim of the present review was to analyze the different methods used to determine TT in mountain runners. After analyzing 1,176 articles found in different databases, 4 articles that presented a relationship with the theme were selected. Varied proposals were observed, in which the surveys searched for physical and/or cardiorespiratory performance, as well as the effect of acclimatization and training at different altitudes in mountain runners. All studies used spirometry to identify the anaerobic threshold through visual methods and a relative mean intensity in thresholds occurred at 80 – 90% of VO2max. The results of studies analyzed evidenced the limited use of methodologies in the identification of exercises for training evaluation and prescription, as well as the use of effective and low-cost alternative methods to determine these thresholds in mountain runners.

Limiares de transição fisiológica em corredores de montanhas: uma revisão sistemática

The identification of physiological transition thresholds (TT) is commonly used for prescribing and evaluating the performance of endurance athletes; however, the methods need further investigation in mountain runner athletes. The aim of the present review was to analyze the different methods used to determine TT in mountain runners. After analyzing 1,176 articles found in different databases, 4 articles that presented a relationship with the theme were selected. Varied proposals were observed, in which the surveys searched for physical and/or cardiorespiratory performance, as well as the effect of acclimatization and training at different altitudes in mountain runners. All studies used spirometry to identify the anaerobic threshold through visual methods and a relative mean intensity in thresholds occurred at 80 – 90% of VO2max. The results of studies analyzed evidenced the limited use of methodologies in the identification of exercises for training evaluation and prescription, as well as the use of effective and low-cost alternative methods to determine these thresholds in mountain runners.

Intermittent hypoxic training for 6 weeks in 3000 m hypobaric hypoxia conditions enhances exercise economy and aerobic exercise performance in moderately trained swimmers.

Athletic endurance performance at sea level can be improved via intermittent hypoxic training (IHT). However, the efficacy of IHT for enhancement of aerobic exercise performance at sea level is controversial because of methodological differences. Therefore, the aim of the study was to determine whether the IHT regimen ameliorates exercise economy and aerobic exercise performance in moderately trained swimmers. A total of 20 moderately trained swimmers were equally assigned to the control group (n=10) training in normoxic conditions and the IHT group (n=10) training at a simulated altitude of 3000 m. They were evaluated for metabolic parameters and skeletal muscle oxygenation during 30 min submaximal exercise on a bicycle, and aerobic exercise performance before and after 6 weeks of training composed of aerobic continuous exercise set at 80% maximal heart rate (HRmax) during 30 min and anaerobic interval exercise set at the exercise load with 90% HRmax measured in pre-test during 30 min (10 times 2 min exercise and 1 min rest). According to the results, the IHT group demonstrated greater improvement in exercise economy due to decreases in VO2 (p=.016) and HHb (p=.002) and increases in O2Hb (p<.001) and TOI (p=.006). VCO2 was decreased in the IHT group (p=.010) and blood lactate level was decreased in the control (p=.005) and IHT groups (p=.001). All aerobic exercise performance including VO2max (p=.001) and the 400 m time trial (p<.001) were increased in the IHT group. The present findings indicate that the 6 week IHT regime composed of high-intensity aerobic continuous exercise and anaerobic interval exercise can be considered an effective altitude/hypoxic training method for improvement of exercise economy and aerobic exercise performance in moderately trained swimmers.

Nutritional Ketosis Alters Fuel Preference and Thereby Endurance Performance in Athletes

Ketosis, the metabolic response to energy crisis, is a mechanism to sustain life by altering oxidative fuel selection. Often overlooked for its metabolic potential, ketosis is poorly understood outside of starvation or diabetic crisis. Thus, we studied the biochemical advantages of ketosis in humans using a ketone ester-based form of nutrition without the unwanted milieu of endogenous ketone body production by caloric or carbohydrate restriction. In five separate studies of 39 high-performance athletes, we show how this unique metabolic state improves physical endurance by altering fuel competition for oxidative respiration. Ketosis decreased muscle glycolysis and plasma lactate concentrations, while providing an alternative substrate for oxidative phosphorylation. Ketosis increased intramuscular triacylglycerol oxidation during exercise, even in the presence of normal muscle glycogen, co-ingested carbohydrate and elevated insulin. These findings may hold clues to greater human potential and a better understanding of fuel metabolism in health and disease.