Maximal Lactate Steady State Intensity Research Articles

A Five-Week Periodized Carbohydrate Diet Does Not Improve Maximal Lactate Steady-State Exercise Capacity and Substrate Oxidation in Well-Trained Cyclists compared to a High-Carbohydrate Diet.

There is a growing interest in studies involving carbohydrate (CHO) manipulation and subsequent adaptations to endurance training. This study aimed to analyze whether a periodized carbohydrate feeding strategy based on a daily training session has any advantages compared to a high-carbohydrate diet in well-trained cyclists. Seventeen trained cyclists (VO2peak = 70.8 ± 6.5 mL·kg-1·min-1) were divided into two groups, a periodized (PCHO) group and a high-carbohydrate (HCHO) group. Both groups performed the same training sessions for five weeks. In the PCHO group, 13 training sessions were performed with low carbohydrate availability. In the HCHO group, all sessions were completed following previous carbohydrate intake to ensure high pre-exercise glycogen levels. In both groups, there was an increase in the maximal lactate steady state (MLSS) (PCHO: 244.1 ± 29.9 W to 253.2 ± 28.4 W; p = 0.008; HCHO: 235.8 ± 21.4 W to 246.9 ± 16.7 W; p = 0.012) but not in the time to exhaustion at MLSS intensity. Both groups increased the percentage of muscle mass (PCHO: p = 0.021; HCHO: p = 0.042) and decreased the percent body fat (PCHO: p = 0.021; HCHO: p = 0.012). We found no differences in carbohydrate or lipid oxidation, heart rate, and post-exercise lactate concentration. Periodizing the CHO intake in well-trained cyclists during a 5-week intervention did not elicit superior results to an energy intake-matched high-carbohydrate diet in any of the measured outcomes.

Critical Velocity, Maximal Lactate Steady State, and Muscle MCT1 and MCT4 after Exhaustive Running in Mice.

Although the critical velocity (CV) protocol has been used to determine the aerobic capacity in rodents, there is a lack of studies that compare CV with maximal lactate steady state intensity (iMLSS) in mice. As a consequence, their physiological and molecular responses after exercise until exhaustion at CV intensity remain unclear. Thus, we aimed to compare and correlate CV with iMLSS in running mice, following different mathematical models for CV estimation. We also evaluated their physiological responses and muscle MCT1 and MCT4 after running until exhaustion at CV. Thirty C57BL/6J mice were divided into two groups (exercised-E and control-C). Group E was submitted to a CV protocol (4 days), using linear (lin1 and lin2) and hyperbolic (hyp) mathematical models to determine the distance, velocity, and time to exhaustion (tlim) of each predictive CV trial, followed by an MLSS protocol. After a running effort until exhaustion at CV intensity, the mice were immediately euthanized, while group C was euthanized at rest. No differences were observed between iMLSS (21.1 ± 1.1 m.min-1) and CV estimated by lin1 (21.0 ± 0.9 m.min-1, p = 0.415), lin2 (21.3 ± 0.9 m.min-1, p = 0.209), and hyp (20.6 ± 0.9 m.min-1, p = 0.914). According to the results, CV was significantly correlated with iMLSS. After running until exhaustion at CV (tlim = 28.4 ± 8,29 min), group E showed lower concentrations of hepatic and gluteal glycogen than group C, but no difference in the content of MCT1 (p = 0.933) and MCT4 (p = 0.123) in soleus muscle. Significant correlations were not found between MCT1 and MCT4 and tlim at CV intensity. Our results reinforce that CV is a valid and non-invasive protocol to estimate the maximal aerobic capacity in mice and that the content of MCT1 and MCT4 was not decisive in determining the tlim at CV, at least when measured immediately after the running effort.

Utility of INSCYD athletic performance software to determine Maximal Lactate Steady State and Maximal Oxygen Uptake in cyclists


 Serious amateur and elite athletes regularly take part in structured physiological testing sessions so that their progress gets tracked and training loads in the training plan correctly prescribed. Commonly, athletes are tested for the maximal oxygen uptake (V̇O2max) and maximal lactate steady state intensity (MLSS). While for the former expensive laboratory equipment is required, the latter requires multiple exercise trials for accurate determination. INSCYD athletic performance software is designed to enable continuous monitoring of these two parameters throughout the season after undertaking a single visit exercise testing session involving blood lactate sampling and power output measurement. The purpose of the present study was to assess validity of the software by its estimates of V̇O2max and MLSS and compare them to gold standard laboratory measures. 11 trained participants (V̇O2max 61.0 ± 7.9 mL ∙ kg-1 ∙ min-1) took part in this study consisting of formal graded V̇O2max test, multiple MLSS trials and a recommended test to obtain the data later fed the INSCYD athletic performance software. Both V̇O2max relative (∆=0.13 ml.kg-1.min-1, p=0.885) and MLSS calculated values (∆=2 W, p=0.655) were within expected daily variation and thus the estimations considered valid. It can be concluded that INSCYD athletic performance software offers its users utility to accurately predict V̇O2max and MLSS provided that the practitioner has a good idea of where the MLSS lies. However, caution is required when interpreting other parameter estimates provided by the software due their questionable scientific validity.

Comparison of different test protocols to determine maximal lactate steady state intensity in swimming

ObjectivesThis study compared step test, lactate minimum (LM) test and reverse lactate threshold (RLT) test protocols with maximal lactate steady state (MLSS) in free-swimming. All test protocols used fixed duration increments and high work-rate resolution (≤ 0.03 m·s−1) to ensure high sensitivity. DesignValidation study. Methods23 swimmers or triathletes (12 male and 11 female) of different ages (19.0 ± 5.9 yrs) and performance levels (400 m personal best 1.38 ± 0.13 m·s−1, FINA points 490 ± 118) completed an incremental step test (+0.03 m·s−1 every 3 min) to determine speed at 4 mmol·L−1 and at modified maximal distance method, a LM test, a RLT test and two to five 30 min tests (±0.015 m·s−1) to determine MLSS. Following a 200 m all-out and a 5 min rest, LM was determined during an incremental segment (+0.03 m·s−1 every 2 min) as the nadir of the speed-lactate curve. After a priming segment with four increments (+0.06 m·s−1), RLT was determined as the lactate apex during a reverse segment (−0.03 m·s−1) every 3 min. ResultsThe mean differences (± limits of agreement) to speed at MLSS were +1.0 ± 4.1% (speed at 4 mmol·L−1), +1.5 ± 3.5% (modified maximum distance method), −0.2 ± 4.7% (LM) and 2.0 ± 3.1% (RLT). All threshold concepts showed good agreement with MLSS pace (intraclass correlation coefficient ≥ 0.886). ConclusionsTest protocols with a fixed step duration and fine increments allowed high accuracy in estimating MLSS pace. With similar criterion agreement to the LM and RLT tests, incremental step tests appear more practicable due to less prior knowledge required and derivation of individual training zones.

Agreement of maximal lactate steady state with critical power and physiological thresholds in rowing

ABSTRACT The aim of this study was threefold: (a) to compare the maximal lactate steady state (MLSS) with critical power (CP); (b) to describe the relationship of MLSS with rowing performances; and (c) to verify the agreement of MLSS with several exercise intensity thresholds in rowers. Fourteen male rowers (mean [SD]: age = 26 [13] years; height = 1.82 [0.05] m; body mass = 81.0 [7.6] kg) performed on a rowing ergometer: (I) discontinuous incremental test with 3 min stages and 30-s recovery intervals (INC3min); (II) continuous incremental test with 60-s stages (INC1min); (III) two to four constant workload tests to determine MLSS; and (IV) performance tests of 500, 1000, 2000 and 6000 m to determine CP. Twenty-seven exercise intensity thresholds based on blood lactate, heart rate and ventilatory responses were determined by incremental tests, and then compared with MLSS. CP (257 [38] W) was higher than MLSS (187 [25] W; p < 0.001), with a very large mean difference (37%), large typical error of estimate (14%) and moderate correlation (r = 0.48). Despite the correlations between MLSS and most intensity thresholds (r > 0.70), all presented low correspondence (TEE > 5%), with a lower bias found between MLSS and the first intensity thresholds (−12.5% to 4.1%). MLSS was correlated with mean power during 500 m (r = 0.65), 1000 m (r = 0.86) and 2000 m (r = 0.78). In conclusion, MLSS intensity is substantially lower than CP and presented low agreement with 27 incremental-derived thresholds, questioning their use to estimate MLSS during rowing ergometer exercise. Highlights MLSS was substantially lower than CP in rowing exercise with a mean difference of 37%, much larger than the difference commonly found in running and cycling exercise (i.e., ?10%). A clear disagreement was reported between MLSS and 27 physiological thresholds determined in different incremental tests. There is a positive association of MLSS with 500, 1000 and 2000 m rowing ergometer performance tests.

Does critical velocity represent the maximal lactate steady state in youth swimmers?

Summary Objectives We investigated the relation between critical velocity (CV) and maximal lactate steady state (MLSS) in swimmers athletes of youth categories. Equipment and methods Twenty well-trained competitive youth swimmers (13.84 ± 0.89 y) participated in the study. CV was determined by the linear regression slope b between the distance and time obtained in four maximal bouts of 50, 100, 200 and 400-meters (m) swimming freestyle each. To determine the MLSS, the subjects randomly performed three series of four bouts of 400 m (3 × 4 × 400 m) with velocity corresponding to 98, 100 and 102% of the CV. We collected 25 μl of blood from their fingertips at rest and at the end of each bout. MLSS intensity was defined as the highest workload that could be maintained for a long period of time in which the blood lactate concentration did not increase more than 1 mmol·L−1. Results CV was significantly higher than velocity corresponding to MLSS in adolescents swimmers (1.31 ± 0.05 vs. 1.29 ± 0.05 m·s−1, P Conclusion Although CV overestimates MLSS in young swimmers, the strong correlation, good agreement and trivial effect size between them suggest that using CV is reliable for prescription and swimming training assessment.

Sex-Related Differences in the Maximal Lactate Steady State.

The maximal lactate steady state (MLSS) is one of the factors that differentiates performance in aerobic events. The purpose of this study was to investigate the sex differences in oxygen consumption (VO2), heart rate (HR), and the respiratory exchange ratio (RER) at the MLSS in well-trained distance runners. Twenty-two (12 female, 10 male) well-trained distance runners (23 ± 5.0 years) performed multiple 30-min steady-state runs to determine their MLSS, during which blood lactate and respiratory gas exchange measures were taken. To interpret the MLSS intensity as a training tool, runners completed a time-to-exhaustion (TTE) run at their MLSS. The relative intensity at which the MLSS occurred was identical between males and females according to both oxygen consumption (83 ± 5 %O2max) and heart rate (89 ± 7 %HRmax). However, female runners displayed a significantly lower RER at MLSS compared to male runners (p < 0.0001; 0.84 ± 0.02 vs. 0.88 ± 0.04, respectively). There was not a significant difference in TTE at MLSS between males (79 ± 17 min) and females (80 ± 25 min). Due to the observed difference in the RER at the MLSS, it is suggested that RER derived estimates of MLSS be sex-specific. While the RER data suggest that the MLSS represents different metabolic intensities for males and females, the relative training load of MLSS appears to be similar in males and female runners.

Non-exhaustive double effort test is reliable and estimates the first ventilatory threshold intensity in running exercise

PurposeThe present study aimed to investigate the reliability of the non-exhaustive double effort (NEDE) test in running exercise and its associations with the ventilatory thresholds (VT1 and VT2) and the maximal lactate steady state (MLSS). MethodsTen healthy male adults (age: 23 ± 4 years, height: 176.6 ± 6.4 cm, body mass: 76.6 ± 10.7 kg) performed 4 procedures: (1) a ramp test for VT1 and VT2 determinations measured by ratio of expired ventilation to O2 uptake (VE/VO2) and expired ventilation to CO2 output (VE/VCO2) equivalents, respectively; (2) the NEDE test measured by blood lactate concentration (NEDELAC) and heart rate responses (NEDEHR); (3) a retest of NEDE for reliability analysis; and (4) continuous efforts to determine the MLSS intensity. The NEDE test consisted of 4 sessions at different running intensities. Each session was characterized by double efforts at the same running velocity (E1 and E2, 180 s), separated by a passive recovery period (90 s rest). LAC and HR values after E1 and E2 (in 4 sessions) were used to estimate the intensity equivalent to “null delta” by linear fit. This parameter represents, theoretically, the intensity equivalent to maximal aerobic capacity. ResultsThe intraclass correlation coefficient indicated significant reliability for NEDELAC (0.93) and NEDEHR (0.79) (both p< 0.05). There were significant correlations, no differences, and strong agreement with the intensities predicted by NEDELAC (10.1 ± 1.9 km/h) and NEDEHR (9.8 ± 2.0 km/h) to VT1 (10.2 ± 1.1 km/h). In addition, despite significantly lower MLSS intensity (12.2 ± 1.2 km/h), NEDELAC and NEDEHR intensities were highly correlated with this parameter (0.90 and 0.88, respectively). ConclusionThe NEDE test applied to running exercise is reliable and estimates the VT1 intensity. Additionally, NEDE intensities were lower but still correlated with VT2 and MLSS.

The Lactate Minimum Test: Concept, Methodological Aspects and Insights for Future Investigations in Human and Animal Models.

In 1993, Uwe Tegtbur proposed a useful physiological protocol named the lactate minimum test (LMT). This test consists of three distinct phases. Firstly, subjects must perform high intensity efforts to induce hyperlactatemia (phase 1). Subsequently, 8 min of recovery are allowed for transposition of lactate from myocytes (for instance) to the bloodstream (phase 2). Right after the recovery, subjects are submitted to an incremental test until exhaustion (phase 3). The blood lactate concentration is expected to fall during the first stages of the incremental test and as the intensity increases in subsequent stages, to rise again forming a “U” shaped blood lactate kinetic. The minimum point of this curve, named the lactate minimum intensity (LMI), provides an estimation of the intensity that represents the balance between the appearance and clearance of arterial blood lactate, known as the maximal lactate steady state intensity (iMLSS). Furthermore, in addition to the iMLSS estimation, studies have also determined anaerobic parameters (e.g., peak, mean, and minimum force/power) during phase 1 and also the maximum oxygen consumption in phase 3; therefore, the LMT is considered a robust physiological protocol. Although, encouraging reports have been published in both human and animal models, there are still some controversies regarding three main factors: (1) the influence of methodological aspects on the LMT parameters; (2) LMT effectiveness for monitoring training effects; and (3) the LMI as a valid iMLSS estimator. Therefore, the aim of this review is to provide a balanced discussion between scientific evidence of the aforementioned issues, and insights for future investigations are suggested. In summary, further analyses is necessary to determine whether these factors are worthy, since the LMT is relevant in several contexts of health sciences.

Aerobic Evaluation in Elite Slalom Kayakers Using a Tethered Canoe System: A New Proposal.

Among other aspects, aerobic fitness is indispensable for performance in slalom canoe. To propose the maximal-lactate steady-state (MLSS) and critical-force (CF) tests using a tethered canoe system as new strategies for aerobic evaluation in elite slalom kayakers. In addition, the relationship between the aerobic parameters from these tests and the kayakers' performances was studied. Twelve male elite slalom kayakers from the Brazilian national team participated in this study. All tests were conducted using a tethered canoe system to obtain the force records. The CF test was applied on 4 d and analyzed by hyperbolic (CFhyper) and linear (CFlin) mathematical models. The MLSS intensity (MLSSint) was obtained by three 30-min continuous tests. The time of a simulated race was considered the performance index. No difference (P < .05) between CFhyper (65.9 ± 1.6 N) and MLSSint (60.3 ± 2.5 N) was observed; however, CFlin (71.1 ± 1.7 N) was higher than MLSSint. An inverse and significant correlation was obtained between MLSSint and performance (r = -.67, P < .05). In summary, MLSS and CF tests on a tethered canoe system may be used for aerobic assessment of elite slalom kayakers. In addition, CFhyper may be used as an alternative low-cost and noninvasive method to estimate MLSSint, which is related with slalom kayakers' performance.

Reliability of time-to-exhaustion and selected psycho-physiological variables during constant-load cycling at the maximal lactate steady-state.

The maximal lactate steady-state (MLSS) is frequently assessed for prescribing endurance exercise intensity. Knowledge of the intra-individual variability of the MLSS is important for practical application. To date, little is known about the reliability of time-to-exhaustion and physiological responses to exercise at MLSS. Twenty-one healthy men (age, 25.2 (SD 3.3) years; height, 1.83 (0.06) m; body mass, 78.9 (8.9) kg; maximal oxygen uptake, 57.1 (10.7) mL·min-1·kg-1) performed 1 incremental exercise test, and 2 constant-load tests to determine MLSS intensity. Subsequently, 2 open-end constant-load tests (MLSS 1 and 2) at MLSS intensity (3.0 (0.7) W·kg-1, 76% (10%) maximal oxygen uptake) were carried out. During the tests, blood lactate concentrations, heart rate, ratings of perceived exertion (RPE), variables of gas exchange, and core body temperature were determined. Time-to-exhaustion was 50.8 (14.0) and 48.2 (16.7) min in MLSS 1 and 2 (mean change: -2.6 (95% confidence interval: -7.8, 2.6)), respectively. The coefficient of variation (CV) was high for time-to-exhaustion (24.6%) and for mean (4.8 (1.2) mmol·L-1) and end (5.4 (1.7) mmol·L-1) blood lactate concentrations (15.7% and 19.3%). The CV of mean exercise values for all other parameters ranged from 1.4% (core temperature) to 8.3% (ventilation). At termination, the CVs ranged from 0.8% (RPE) to 11.8% (breathing frequency). The low reliability of time-to-exhaustion and blood lactate concentration at MLSS indicates that the precise individual intensity prescription may be challenging. Moreover, the obtained data may serve as reference to allow for the separation of intervention effects from random variation in our sample.

The midpoint between ventilatory thresholds approaches maximal lactate steady state intensity in amateur cyclists.

The aim was to determine whether the midpoint between ventilatory thresholds (MPVT) corresponds to maximal lactate steady state (MLSS). Twelve amateur cyclists (21.0 ± 2.6 years old; 72.2 ± 9.0 kg; 179.8 ± 7.5 cm) performed an incremental test (25 W·min-1) until exhaustion and several constant load tests of 30 minutes to determine MLSS, on different occasions. Using MLSS determination as the reference method, the agreement with five other parameters (MPVT; first and second ventilatory thresholds: VT1 and VT2; respiratory exchange ratio equal to 1: RER = 1.00; and Maximum) was analysed by the Bland-Altman method. The difference between workload at MLSS and VT1, VT2, RER=1.00 and Maximum was 31.1 ± 20.0, -86.0 ± 18.3, -63.6 ± 26.3 and -192.3 ± 48.6 W, respectively. MLSS was underestimated from VT1 and overestimated from VT2, RER = 1.00 and Maximum. The smallest difference (-27.5 ± 15.1 W) between workload at MLSS and MPVT was in better agreement than other analysed parameters of intensity in cycling. The main finding is that MPVT approached the workload at MLSS in amateur cyclists, and can be used to estimate maximal steady state.

Estimation of the Maximal Lactate Steady State Intensity by the Rating of Perceived Exertion.

The maximal lactate steady state is the gold standard for evaluating aerobic capacity; however, it is time-consuming. The lactate minimum protocol is an easier alternative, but is not feasible and still expensive. This study investigated whether the rating of perceived exertion of 13 is an accurate predictor of lactate minimum and maximal lactate steady state intensities. Eleven physically active men performed three tests: (1) incremental exercise with workloads based on rating of perceived exertion of 10, 13, and 16 (experimental protocol - denominated RPE-13 test), (2) lactate minimum, and (3) maximal lactate steady state. No differences were observed among participants' workloads corresponding to rating of perceived exertion 13, lactate minimum, and maximal lactate steady state intensities. Thus, the workload associated with the rating of perceived exertion of 13 was equivalent to the other two protocols investigated.

Muscle glycogen metabolism changes in rats fed early postnatal a fructose-rich diet after maternal protein malnutrition: effects of acute physical exercise at the maximal lactate steady-state intensity.

BackgroundThe objective was to evaluate the muscle glucose metabolism in rats fed a fructose-rich diet after fetal protein malnutrition, at rest and after acute physical exercise at maximal lactate steady-state intensity.MethodsThe male offspring born of mothers fed on a balanced or low-protein diet were split in four groups until 60 days: Balanced (B): balanced diet during the whole period; Balanced/Fructose (BF): balanced diet in utero and fructose-rich diet after birth; Low protein/Balanced (LB): low-protein diet in utero and balanced diet after birth; Low protein/Fructose (LF): low protein diet in utero and fructose-rich diet after birth.ResultsAcute physical exercise reduced the muscle glycogen concentrations in all groups, although the LF group showed higher concentrations at rest. There was no difference among the groups in the glucose uptake and oxidation rates in the isolated soleus muscle neither at rest nor after acute exercise. However, glycogen synthesis was higher in the LF muscle than in the others at rest. Acute physical exercise increased glycogen synthesis in all groups, and the LF group showed the highest values.ConclusionThe fructose-rich diet administered in rats after fetal protein malnutrition alters muscle glycogen concentrations and glycogen synthesis in the rest and after acute exercise at maximal lactate steady-state intensity.

Maximal power output estimates the MLSS before and after aerobic training

The purpose of this study is to present an equation to predict the maximal lactate steady state (MLSS) through a VO2peak incremental protocol. Twenty-six physically active men were divided in two groups (G1 and G2). They performed one maximal incremental test to determine their VO2peak and maximal power output (Wpeak), and also several constant intensity tests to determine MLSS intensity (MLSSw) on a cycle ergometer. Group G2 underwent six weeks of aerobic training at MLSSw. A regression equation was created using G1 subjects Wpeak and MLSSw to estimate the MLSS intensity (MLSSweq) before and after training for G2 (MLSSweq = 0.866 x Wpeak-41.734). The mean values were not different (150±27W vs 148±27W, before training / 171±26W vs 177±24W, after training) and significant correlations were found between the measured and the estimated MLSSw before (r²=0.49) and after training (r²=0.62) in G2. The proposed equation was effective to estimate the MLSS intensity before and after aerobic training.

Resposta cardiorrespiratória e gasto energético em exercício na máxima fase estável de lactato

A resposta cardiorrespiratoria durante exercicios submaximos, na intensidade da maxima fase estavel de lactato (MFELint) ate a exaustao, tem sido pouco investigada. O objetivo deste estudo foi investigar a resposta do consumo de oxigenio (VO2), frequencia cardiaca (FC) e pulso de oxigenio (pulso O2) em exercicio realizado na MFELint ate a exaustao, e comparar o gasto energetico (GE) estimado pelo VO2 e pela FC. Doze sujeitos treinados realizaram um protocolo incremental em cicloergometro para determinar parâmetros maximos e submaximos do metabolismo aerobio. Posteriormente, foram realizados 2 a 4 testes de 30 min com carga constante para identificar a MFELint. Finalmente, os sujeitos realizaram um teste ate a exaustao na MFELint. Os parâmetros cardiorrespiratorios foram medidos continuamente durante todos os testes. No teste de exaustao, as respostas fisiologicas foram comparadas entre seis momentos relativos do tempo de exaustao (TTE). O TTE medio foi 55,1±10,2 min. O pulso de O2 apresentou reducoes significativas ao longo do tempo, atingindo, no momento da exaustao, um valor ~ 9% inferior comparado ao inicio do exercicio. Este fato ocorreu pelo aumento da FC ao longo do tempo de forma desproporcional ao aumento do VO2, resultando em diferencas significantes entre os GE estimados. Portanto, em exercicio realizado na MFELint ate a exaustao, parece existir uma perda gradual da eficiencia cardiorrespiratoria, evidenciada pela reducao do pulso O2. Assim, a relacao direta entre VO2 e FC com a carga de trabalho e alterada ao longo do exercicio, conduzindo a erros de estimativa do GE a partir dos valores da FC.

Time to Exhaustion at Continuous and Intermittent Maximal Lactate Steady State During Running Exercise

The purpose of this study was to determine and compare the time to exhaustion (TE) and the physiological responses at continuous and intermittent (ratio 5:1) maximal lactate steady state (MLSS) in well-trained runners. Ten athletes (32.7 ± 6.9 y, VO2max 61.7 ± 3.9 mL · kg-1 · min-1) performed an incremental treadmill test, three to five 30-min constant-speed tests to determine the MLSS continuous and intermittent (5 min of running, interspaced by 1 min of passive rest), and 2 randomized TE tests at such intensities. Two-way ANOVA with repeated measures was used to compare the changes in physiological variables during the TE tests and between continuous and intermittent exercise. The intermittent MLSS velocity (MLSSint = 15.26 ± 0.97 km/h) was higher than in the continuous model (MLSScon = 14.53 ± 0.93 km/h), while the TE at MLSScon was longer than MLSSint (68 ± 11 min and 58 ± 15 min, P < .05). Regarding the cardiorespiratory responses, VO2 and respiratory-exchange ratio remained stable during both TE tests while heart rate, ventilation, and rating of perceived exertion presented a significant increase in the last portion of the tests. The results showed a higher tolerance to exercising during MLSScon than during MLSSint in trained runners. Thus, the training volume of an extensive interval session (ratio 5:1) designed at MLSS intensity should take into consideration this higher speed at MLSS and also the lower TE than with continuous exercise.

Exercise Training at MLSS Decreases Weight Gain and Increases Aerobic Capacity in Obese Zucker Rats

This study aimed to identify the aerobic capacity enhancement and subsequent body weight (BW) status of obese Zucker rats (OZRs) after 4 weeks of treadmill running exercise at the maximal lactate steady state (MLSS). In addition to obese Zucker rats (OZRs), lean Wistar Kyoto rats (WKYs) were used, and both species were divided into control and exercise groups as follows: obese exercise (OZR-EX, n=5), obese control (OZR-CON, n=5), lean exercise (WKY-EX, n=5) and lean control (WKY-CON, n=5). The OZR and WKY exercise groups trained 5 days per week at 12.5 m.min-1 and 20 m.min-1, respectively. After 4 weeks of training, MLSS was ascertained to evaluate the animals' aerobic capacity using 3 different velocities (12.5, 15 and 17.5 m.min-1 for OZRs and 25, 30 and 35 m.min-1 for WKYs). The MLSS of OZR-EX was identified at the velocity of 15 m.min-1, representing a 20% increase in aerobic capacity after the exercise program. The MLSS of WKY-EX was identified at 30 m.min-1 with a 50% increase of in aerobic capacity. Obese animals that exercised showed reduced weight gain compared to the non-exercise obese control group (p <0.05). Our results thus show that exercise training at MLSS intensity increased the aerobic capacity in both obese and non-obese animals and also reduced BW gain.

Continuous and intermittent running to exhaustion at maximal lactate steady state: Neuromuscular, biochemical and endocrinal responses

The aim of the present study was to characterize the neuromuscular, biochemical, and endocrinal responses from a running to exhaustion mode at the maximal lactate steady state intensity during continuous and intermittent protocols. Pre-post test measures. Twelve athletes performed an incremental treadmill test, several constant speed tests to determine the maximal lactate steady state at continuous and intermittent (5:1 ratio) models and two randomized tests until exhaustion at such intensities. Knee extension torque and blood sampling were collected before and immediately after the time to exhaustion tests. The results showed a significant decrement (∼15%) in torque production after time to exhaustion tests for both exercise models. In addition to neuromuscular impairment, an acute increase of 65% and 38% was observed creatine kinase, during continuous and intermittent running, respectively. Regarding hormonal responses when compared to baseline measurements, cortisol increased by 132% and 121% in the continuous and intermittent protocols, respectively. No correlation was found between biochemical, endocrinal and the neuromuscular variables. The present findings showed that running until exhaustion performed at maximal lactate steady state, significantly impaired muscle strength and increased hormonal and muscle damage markers in two different protocols (i.e. continuous and intermittent) amongst trained runners.

Combination of l-arginine supplementation and exercise performance on blood pressure responses in normotensive and hypertensive postmenopausal women: A crossover study

The purpose of this study was to evaluate the effects of l -arginine supplementation associated with exercise performance on the blood pressure (BP) regulation in normotensive (NT, n = 16) and hypertensive (HT, n = 7) postmenopausal women using a cross-over methodology. In four different days randomly, resting BP was measured and 9 g of l -arginine were given orally for the volunteers (Ajinomoto, Japan). Forty-five minutes after, the participants performed 30 min of exercise on treadmill at the maximal lactate steady state intensity. Blood venous was collected before the l -arginine supplementation and 45 min after the end of the exercise (ARG-EXE day). During the others three days, the volunteers performed exercise taking placebo pills (EXE day), or only l -arginine without exercise (ARG day), or did not take l -arginine nor performed exercise (CON day). Plasma Nitrite/Nitrate (NOx – Cayman, MI, USA) and cyclic guanosine monophosphate (cGMP – R&D systems, MN, USA) levels were measured by ELISA method. Women were overweight and non-diabetic. In NT women, systolic BP was 43% and 100% lower in EXE and ARG-EXE, respectively. Diastolic BP was 42% lower only in ARG-EXE comparing with CON day. No difference was found in NOx, but cGMP levels were higher in the ARG-EXE day (190%) comparing with CON day. in HT women, systolic BP was 70% and 40% lower in EXE and ARG-EXE days, respectively which was not accompanied by any changing in NOx or cGMP levels. In NT women, l -arginine plus exercise improve both systolic and diastolic BP that was positively associated with cGMP levels.