Cardiorespiratory and metabolic determinants during moderate and high resistance exercise intensities until exhaustion using dynamic leg press: comparison with critical load.

The objective of this study was to assess cardiovascular, respiratory, and metabolic responses during a commonly used dynamic leg press resistance exercise until exhaustion (TEx) at different intensities and compare with critical load (CL). This was a prospective, cross-sectional, controlled, and crossover study. Twelve healthy young men (23±2.5 years old) participated. The subjects carried out three bouts of resistance exercise in different percentages of 1 repetition maximum (60, 75, and 90% 1RM) until TEx. CL was obtained by means of hyperbolic model and linearization of the load-duration function. During all bout intensities, oxygen uptake (VO2), carbon dioxide production (VCO2), ventilation (VE), and respiratory exchange ratio (RER) were obtained. Variations (peak-rest=Δ) were corrected by TEx. In addition, systolic and diastolic blood pressure (SBP and DBP), blood lactate concentration [La-] and Borg scores were obtained at the peak and corrected to TEx. CL induced greater TEx as well as number of repetitions when compared to all intensities (P<0.001). During CL, Borg/TEx, ΔSBP/TEx, ΔDBP/TEx, and [La-] were significantly lower compared with 90% load (P<0.0001). In addition, VO2, VCO2, VE, and RER were higher during CL when compared to 90 or 75%. TEx was significantly correlated with VO2 on CL (r=0.73, P<0.05). These findings support the theory that CL constitutes the intensity that can be maintained for a very long time, provoking greater metabolic and ventilatory demand and lower cardiovascular and fatigue symptoms during resistance exercise.

Cardiorespiratory and metabolic determinants during moderate and high resistance exercise intensities until exhaustion using dynamic leg press: comparison with critical load

The objective of this study was to assess cardiovascular, respiratory, and metabolic responses during a commonly used dynamic leg press resistance exercise until exhaustion (TEx) at different intensities and compare with critical load (CL). This was a prospective, cross-sectional, controlled, and crossover study. Twelve healthy young men (23±2.5 years old) participated. The subjects carried out three bouts of resistance exercise in different percentages of 1 repetition maximum (60, 75, and 90% 1RM) until TEx. CL was obtained by means of hyperbolic model and linearization of the load-duration function. During all bout intensities, oxygen uptake (VO2), carbon dioxide production (VCO2), ventilation (VE), and respiratory exchange ratio (RER) were obtained. Variations (peak-rest=Δ) were corrected by TEx. In addition, systolic and diastolic blood pressure (SBP and DBP), blood lactate concentration [La-] and Borg scores were obtained at the peak and corrected to TEx. CL induced greater TEx as well as number of repetitions when compared to all intensities (P<0.001). During CL, Borg/TEx, ΔSBP/TEx, ΔDBP/TEx, and [La-] were significantly lower compared with 90% load (P<0.0001). In addition, VO2, VCO2, VE, and RER were higher during CL when compared to 90 or 75%. TEx was significantly correlated with VO2 on CL (r=0.73, P<0.05). These findings support the theory that CL constitutes the intensity that can be maintained for a very long time, provoking greater metabolic and ventilatory demand and lower cardiovascular and fatigue symptoms during resistance exercise.

Hepatocellular carcinoma and estrogen receptors: Polymorphisms and isoforms relations and implications.

Hepatocellular carcinoma (HCC) is the most common primary tumor of liver and its incidence continues to increase worldwide. HCC is a disease with multifactorial causes and genetic variability has been discussed as a risk factor for its development. Liver is a hormone-sensitive organ and therefore is influenced by gonadal hormones, such as estrogen. Estrogen is known to participate in various biological functions, but its role in development of HCC, on the other hand, is controversial and presents evidence suggesting a role as both a carcinogen and protective effect in liver. Estrogen way of action is mediated by estrogen receptor alpha (ERα) and estrogen receptor beta (ERß), that belong to a family of nuclear receptors that may regulate the expression of many genes. The ER subtypes exert a variety of roles in many stages of liver disease and may play a part in the process of signal transduction, according to some studies. However, the many functions of ER subtypes in hepatic diseases, in special of the ERß, are yet to be clarified. The genetic modifications related to HCC are not yet fully clarified and accumulation of multiple genetic alterations appears to have an important role in carcinogenesis of HCC. The presence of some certain single nucleotide polymorphism (SNP) may have a functional repercussion related to final product of a gene, which can be measured and may participate in some alterations related to a pathological condition. Our hypothesis is based on the fact that liver tissue express ER and its different variants exert multiple functions in various stages of liver disease and participate in an extremely complicated signal transduction process, therefore we believe that the presence of one or more SNPs of ESR1 and ESR2 genes may be related with the increase of risk in developing and the severity of HCC, as well as in the response to different treatments. The confirmation of our hypothesis by scientific studies may provide knowledge of markers that act as prognostic factors of this disease, as well as enabling alternatives to development of anti tumoral therapies.

Increased lactate threshold after five weeks of treadmill aerobic training in rats.

The aim of the present study was to analyse the lactate threshold (LT) changes in rats submitted to an aerobic treadmill-training programme. Twenty-five Wistar rats were divided into two groups: a sedentary control group (CG), and a trained group (TG) submitted to an aerobic training during 5 weeks. All the animals were submitted to an incremental treadmill exercise test in order to determine LT. There was an increase in the maximum running speed in the TG (from 32.25 ± 1.27 to 47.75 ± 3.13 m.min-1 - p = 0.001), and running speed at LT (from 26.21 ± 1.15 to 35.30 ± 2.24 m.min-1 - p = 0.004), a part from the reduction in blood lactate at LT. LT can be determined in rats, and aerobic training induced positive oxidative physiological adaptations in the animals.

Increased lactate threshold after five weeks of treadmill aerobic training in rats / Aumento do limiar de lactato após cinco semanas de treinamento aeróbio em esteira em ratos

The aim of the present study was to analyse the lactate threshold (LT) changes in rats submitted to an aerobic treadmill-training programme. Twenty-five Wistar rats were divided into two groups: a sedentary control group (CG), and a trained group (TG) submitted to an aerobic training during 5 weeks. All the animals were submitted to an incremental treadmill exercise test in order to determine LT. There was an increase in the maximum running speed in the TG (from 32.25 ± 1.27 to 47.75 ± 3.13 m.min–1 – p = 0.001), and running speed at LT (from 26.21 ± 1.15 to 35.30 ± 2.24 m.min–1 – p = 0.004), a part from the reduction in blood lactate at LT. LT can be determined in rats, and aerobic training induced positive oxidative physiological adaptations in the animals.

O objetivo do presente estudo foi analisar as mudanças no limiar de lactato (LL) em ratos submetidos a um programa de treinamento aeróbio em esteira. Vinte e cinco ratos Wistar foram divididos em dois grupos: um grupo controle sedentário (CG), e um grupo treinado (GT) submetido a um treinamento aeróbio durante 5 semanas. Todos os animais foram submetidos a um teste de exercício incremental em esteira, a fim de determinar o LL. Houve um aumento na velocidade máxima de corrida no GT (de 32,25 ± 1,27 para 47,75 ± 3,13 m.min–1 - p = 0,001), e velocidade de corrida no LL (de 26,21 ± 1,15 para 35,30 ± 2,24 m.min–1 - p = 0,004), além da redução na concentração de lactato no LL. O LL pode ser determinado em ratos e o treinamento aeróbio induziu a adaptações fisiológicas oxidativas positivas nos animais.

Effects of long-term periodized resistance training on body composition, leptin, resistin and muscle strength in elderly post-menopausal women.

AIM: Objective of the study was to determine the effects of a periodized resistance training program on body composition, plasmatic levels of leptin and resistin, and muscle strength in elderly post-menopausal women. METHODS: Twenty-three post-menopausal women (age= 63.02±4.42 years; height 1.55±0.06 m; body mass 67.56±2.26 kg) were submitted to 12 months of periodized resistance training twice a week. The training program consisted of 3 sets of 6-14 repetitions maximal (RM). Body composition (DXA), muscle strength (bench press, leg press 45º and arm curl), plasmatic levels of resistin and leptin (ELISA method) were assessed before and after the training program. Paired Student's t test was used for comparison between pre- and post-training values. RESULTS: There was a significant increase in muscle strength and lean body mass; decrease in body mass, body fat percentage and fat mass after 12 months of resistance training, a part from the decrease in leptin and resistin levels. CONCLUSION: Long-term periodized resistance training prevents aging sarcopenia, decreases body fat and systemic markers of inflammation in postmenopausal elderly women.

MMP(-2) expression in skeletal muscle after strength training.

The aim of this study was to assess the effects of resistance training on ladders (RTL) on MMP(-2) expression and blood lactate concentration [La-]. 30 male (3 months of age), albino rats were divided into 3 groups: sedentary control (SC, n=10), low resistance exercise training (Low-IntRT, n=10) and high-intensive exercise training (High-IntRT, n=10). Animals of High-IntRT were submitted to a progressively increasing overload in relation to body weight until exhaustion, while the Low-IntRT group performed the same exercise regimen with no external load. The program had a frequency of 3 times per week over 8 weeks. MMP(-2) expression of tibialis anterior muscle and [La-] were measured. While there was a significant increase of MMP(-2) (pro-form) in both groups, only High-IntRT significantly increased MMP(-2) in active-form (p<0.05). Both trained groups exhibited an increase in [La-] when compared to controls, however, the increase in [La-] was significantly higher in the High-IntRT compared to Low-IntRT (p<0.05). Strong correlation was found between MMP(-2) (active form) and [La-] in High-IntRT (r=0.91). RTL in using low and high-intensity exercise can serve as a model to demonstrate different responses of MMP(-2) expression in an animal model. It appears active form expression of MMP(-2) is modulated by exercise intensity.

Acute cardiorespiratory and metabolic responses during resistance exercise in the lactate threshold intensity.

The aims were both to determine lactate and ventilatory threshold during incremental resistance training and to analyze the acute cardiorespiratory and metabolic responses during constant-load resistance exercise at lactate threshold (LT) intensity. Ten healthy men performed 2 protocols on leg press machine. The incremental test was performed to determine the lactate and ventilatory thresholds through an algorithmic adjustment method. After 48 h, a constant-load exercise at LT intensity was executed. The intensity of LT and ventilatory threshold was 27.1±3.7 and 30.3±7.9% of 1RM, respectively (P=0.142). During the constant-load resistance exercise, no significant variation was observed between set 9 and set 15 for blood lactate concentration (3.3±0.9 and 4.1±1.4 mmol x L(-1), respectively. P=0.166) and BORG scale (11.5±2.9 and 13.0±3.5, respectively, P=0.783). No significant variation was observed between set 6 and set 15 for minute ventilation (19.4±4.9 and 22.4±5.5 L x min(-1), respectively, P=0.091) and between S3 and S15 for VO2 (0.77±0.18 and 0.83±0.16 L x min(-1), respectively, P=1.0). Constant-load resistance exercise at LT intensity corresponds to a steady state of ventilatory, cardio-metabolic parameters and ratings of perceived exertion.

Effects of resistance training on matrix metalloproteinase-2 activity and biomechanical and physical properties of bone in ovariectomized and intact rats.

The purpose of this study was to investigate the influence of resistance training on the activity of matrix metalloproteinase (MMP)-2 and bone biomechanical properties in ovariectomized and intact rats. Forty-eight female rats were divided into two distinct groups, ovariectomized (OVX) and intact (Int), which were subdivided into three similar subgroups: sedentary, acute exercise and chronic exercise. Rats performed a resistance training for 12 weeks in which animals climbed a vertical ladder of 1.1 m with weights attached to their tails. Sessions were performed with an interval of 3, 4-9 and 8-12 days scaled dynamic movements of climbing. Biomechanical and physical analyses were performed using a universal testing machine, and MMP-2 activity analysis by zymography. Bone density (BD), mineral density (MD), maximum load and fracture load was reduced in sedentary and acute exercise OVX groups compared with the sedentary intact group (P<0.05); in contrast, chronically trained groups (OVX and Int) showed a significant increase in BD, MD and fracture load compared with all the other groups. MMP-2 activity in chronically trained groups also showed a significant increase, while the sedentary OVX group showed a decrease in MMP-2 activity compared with the intact sedentary group (P<0.05). Our results suggest that the resistance training proposed in our work was efficient in reverting the deleterious effects of ovariectomy on bone tissue, and also produced modeling effects in intact rats. On the other hand, ovariectomy reduced the activity of MMP-2 and produced deleterious effects on bone tissue, mimicking menopause intrinsically.

L-carnitine as an ergogenic aid for patients with chronic obstructive pulmonary disease submitted to whole-body and respiratory muscle training programs.

The effects of adding L-carnitine to a whole-body and respiratory training program were determined in moderate-to-severe chronic obstructive pulmonary disease (COPD) patients. Sixteen COPD patients (66 +/- 7 years) were randomly assigned to L-carnitine (CG) or placebo group (PG) that received either L-carnitine or saline solution (2 g/day, orally) for 6 weeks (forced expiratory volume on first second was 38 +/- 16 and 36 +/- 12%, respectively). Both groups participated in three weekly 30-min treadmill and threshold inspiratory muscle training sessions, with 3 sets of 10 loaded inspirations (40%) at maximal inspiratory pressure. Nutritional status, exercise tolerance on a treadmill and six-minute walking test, blood lactate, heart rate, blood pressure, and respiratory muscle strength were determined as baseline and on day 42. Maximal capacity in the incremental exercise test was significantly improved in both groups (P < 0.05). Blood lactate, blood pressure, oxygen saturation, and heart rate at identical exercise levels were lower in CG after training (P < 0.05). Inspiratory muscle strength and walking test tolerance were significantly improved in both groups, but the gains of CG were significantly higher than those of PG (40 +/- 14 vs 14 +/- 5 cmH2O, and 87 +/- 30 vs 34 +/- 29 m, respectively; P < 0.05). Blood lactate concentration was significantly lower in CG than in PG (1.6 +/- 0.7 vs 2.3 +/- 0.7 mM, P < 0.05). The present data suggest that carnitine can improve exercise tolerance and inspiratory muscle strength in COPD patients, as well as reduce lactate production.

L-carnitine as an ergogenic aid for patients with chronic obstructive pulmonary disease submitted to whole-body and respiratory muscle training programs

The effects of adding L-carnitine to a whole-body and respiratory training program were determined in moderate-to-severe chronic obstructive pulmonary disease (COPD) patients. Sixteen COPD patients (66 ± 7 years) were randomly assigned to L-carnitine (CG) or placebo group (PG) that received either L-carnitine or saline solution (2 g/day, orally) for 6 weeks (forced expiratory volume on first second was 38 ± 16 and 36 ± 12 percent, respectively). Both groups participated in three weekly 30-min treadmill and threshold inspiratory muscle training sessions, with 3 sets of 10 loaded inspirations (40 percent) at maximal inspiratory pressure. Nutritional status, exercise tolerance on a treadmill and six-minute walking test, blood lactate, heart rate, blood pressure, and respiratory muscle strength were determined as baseline and on day 42. Maximal capacity in the incremental exercise test was significantly improved in both groups (P < 0.05). Blood lactate, blood pressure, oxygen saturation, and heart rate at identical exercise levels were lower in CG after training (P < 0.05). Inspiratory muscle strength and walking test tolerance were significantly improved in both groups, but the gains of CG were significantly higher than those of PG (40 ± 14 vs 14 ± 5 cmH2O, and 87 ± 30 vs 34 ± 29 m, respectively; P < 0.05). Blood lactate concentration was significantly lower in CG than in PG (1.6 ± 0.7 vs 2.3 ± 0.7 mM, P < 0.05). The present data suggest that carnitine can improve exercise tolerance and inspiratory muscle strength in COPD patients, as well as reduce lactate production.

Adaptação enzimática da LDH em ratos submetidos a treinamento aeróbio em esteira e laser de baixa intensidade / Adaptation of LDH enzyme in rats undergoing aerobic treadmill training and low intensity laser therapy

OBJETIVO: Verificar a atividade e padrão eletroforético da LDH em resposta ao exercício em esteira em ratos submetidos à fotoestimulação por laser de baixa intensidade (780 etam). MÉTODO: Foram utilizados nesse estudo 54 ratos machos jovens (30dias), Winstar, com peso inicial médio de 112 ± 4,7g, os quais foram divididos em quatro grupos: dois permaneceram em repouso, GRC (grupo repouso controle, n= 9) e GRL (grupo repouso laser, n= 10), sendo o segundo irradiado por laser, e outros dois foram submetidos ao treinamento aeróbio e testes de esforço crescente em esteira (em degraus descontínuos) visando à determinação do limiar de anaerobiose (LA) durante 5 semanas, GEC (grupo exercício controle, n= 16) e GEL (grupo exercício laser, n= 19), sendo o último também irradiado por laser. O laser foi aplicado no quadríceps, glúteo máximo, sóleo e tibial anterior (TA), bilateralmente, imediatamente após cada sessão de treinamento, usando: 3,8J/cm², 15mW, 10s, modo contínuo, durante 5 semanas. Amostras de sóleo, TA e coração foram removidas 48 horas após a última sessão de exercício para análise eletroforética e espectrofotométrica. A estatística foi realizada através do teste ANOVA e post-hoc de TUKEY. O nível de significância foi considerado (p< 0,05). RESULTADOS: Foram observadas reduções na atividade da LDH causadas pelo laser (de 19 por cento a 30 por cento), exercício (de 41 por cento a 66 por cento) e as ações combinadas (de 47 por cento a 66 por cento) (p< 0,01). A eletroforese mostrou uma predominância da subunidade B para o sóleo e coração, e uma predominância da subunidade A no TA. CONCLUSÕES: Estes dados sugerem uma melhor resposta adaptativa dos animais ao treinamento aeróbio associado à terapia laser, no que se refere à otimização da via oxidativa.

Limiar de anaerobiose em ratos submetidos a treinamento fisico em esteira e laser de baixa intensidade / Anaerobic threshold in rats subjected to aerobic treadmill training program and low-intensity laser

O proposito deste estudo foi verificar o limiar de anaerobiose em resposta ao exercicio em estera em ratos submetidos a fotoestimulacao por laser de baixa intensidade (780nm). Metodo: foram utilizados neste estudo 40 ratos machos jovens (30dias), wistar com peso inicial medio de 111+-10g, os quais foram divididos em dois grupos: 1-grupo exercicio controle (GEC) e 2-grupo exercicio laser (GEL), ambos submetidos a um treinamento aerobio em esteira e a testes de esforco crescente (em degraus descontinuos) visando a determinacao do limiar de anaerobiose. O laser foi aplicado nos principais musculos da marcha, imediatamente apos cada sessao de treinamento. Para a dosagem do lactato utilizou-se um lactimetro. A estatistica foi realizada por meio dos testes ANOVA e post-hoc de TUKEY. O nivel de significancia foi considerado (p<-0,05). resultados: apos o periodo de treinamento os dois grupos exibiram aumento na velocidade maxima da corrida e o limiar de anaerobiose se mostrou deslocado para um nivel de maior esforco (p<0,01). As medidas de lactacidemia mostraram ligeira reducao durante a obtencao do limiar de anaerobiose, sobretudo no GEC. Entretanto, nao houve diferenca estatisticamente significativa entre os grupos para as variaveis analisadas, apesar de o GEL ter mostrado comportamento diferenciado no decorrer das semanas, no que se refere ao padrao da curva de esforco. Conclusoes: esses dados sugerem que alteracoes na lactacidemia, em ratos treinados, permitem a determinacao do limiar de anaerobiose e que o treinamento aerobico possibilitou adaptacoes fisiologicas no sentido de aumento na capacidade oxidativa dos animais

Relationships and significance of lactate minimum, critical velocity, heart rate deflection and 3 000 m track-tests for running.

AIM: The running velocities associated to lactate minimum (V(lm)), heart rate deflection (V(HRd)), critical velocity (CV), 3.000 m (V(3000)) and 10 000 m performance (V10km) were compared. Additionally the ability of V(lm) and V(HRd) on identifying sustainable velocities was investigated. METHODS: Twenty runners (28.5+/-5.9 y) performed 1) 3,000 m running test for V3000; 2) an all-out 500 m sprint followed by 6x800 m incremental bouts with blood lactate ([lac]) measurements for V(lm); 3) a continuous velocity-incremented test with heart rate measurements at each 200 m for V(HRd); 4) participants attempted to 30 min of endurance test both at V(lm)(ETV(lm)) and V(HRd)(ETV(HRd)). Additionally, the distance-time and velocity-1/time relationships produced CV by 2 (500 m and 3 000 m) or 3 predictive trials (500 m, 3,000 m and distance reached before exhaustion during ETV(HRd)), and a 10 km race was recorded for V10km. RESULTS: The CV identified by different methods did not differ to each other. The results (m.min(-1)) revealed that V(lm) (281+/-14.8)

Lactate and glucose minimum speeds and running performance.

This study aimed to analyse the validity of glucose minimum speed (GMS) for lactate minimum speed (LMS) assessment during running and their relationship to endurance performance. Eight male trained runners (28.7 +/- 9.0 years) volunteered to take part in this study and underwent an official 10-km road race and a track lactate minimum test (LMT) (0.5-km sprint plus 6 x 800 m from 87 to 98% of maximal 3-km speed). Lactate and glucose minimum speeds were considered those related to the minimum blood lactate and glucose concentrations respectively attained during the graded phase of LMT. Significant correlations (p < 0.05) were found between LMS and GMS (r = 0.72) and LMS and 10-km performance (r = 0.83), but not between GMS and 10-km performance (r = 0.49). No significant differences (p > 0.05) were found between LMS (4.75 +/- 0.08 m/s), GMS (4.73 +/- 0.07 m/s) and 10-km mean speed (4.79 +/- 0.17 m/s). In conclusion, we found GMS to be a good predictor of LMS during track LMT, LMS being well related to endurance running performance.

Stage length, spline function and lactate minimum swimming speed.

AIM: Lactate minimum test (LMT) has become popular in running evaluation. This study analysed the influence of different stage lengths and determination methods on lactate minimum swimming speed (LMS) and its validity for maximal lactate steady-state speed (MLSS-S) assessment. METHODS: Twelve male swimmers (19.7+/-1.6 years, 70.3+/-8.7 kg, 181.4+/-7.9 cm) randomly underwent 4-5 evaluations in a 2-week period. LMS was accessed by simple visualisation (SV) and spline function (SF) methods during 200 and 300 m stages LMT (LMT200 and LMT300, respectively), and MLSS-S was determined during constant speed 2000 m efforts. RESULTS: Respectively, SV and SF provided LMS during LMT200 (1.31+/-0.12 m x s-1 and 1.32+/-0.10 m x sec-1) and LMT300 (1.28+/-0.11 m x sec-1 and 1.28+/-0.10 m x sec-1) which were not significantly different (p>0.05) from each other. However, LMS accessed during LMT200 were significantly greater (p<0.05) than MLSS-S (1.25+/-0.06 m x sec-1). In addition, significant relationships (r=0.79 to 0.98; p<0.05) were found between all studied speeds and lactate minimum values during LMT300 were not significantly different (p>0.05) from those found during LMT200 (5.4+/-2.2 and 5.5+/-2.2 mM vs 6.8+/-2.5 and 7.0+/-2.6 mM, respectively for SV and SF). CONCLUSIONS: Our results suggest that LMS is not affected by different stage lengths and determination METHODS: However, LMT300 results seems to provide a more accurate MLSS-S prediction, being adequate for swimmers evaluation.

Comparaçäo de duas técnicas de treinamento muscular respiratório em pacientes sob ventilaçäo mecânica com insucesso de desmame / Comparison of two techniques of respiratory muscular training in patients under mechanical ventilation with weaning failure

Os objetivos deste estudo foram investigar a existência de diferenças na evolução dos parâmetros de Pressão respiratória máxima (PImáx e PEmáx), do Volume Corrente (VC), Volume minuto (Vm), índice de Tobin e índice de oxigenação, em pacientes sob Ventilação Mecânica (VM), submetidos a um Treinamento Muscular Respiratórios (TMR), verificar se esse tipo de intervenção contribui para o sucesso de desmanche da VM e comparar os dois tipos de TMR utilizados. Foram estudados 45 pacientes com mais de uma semana sob VM e com pelo menos uma tentativa de desmame, mal sucedida. Destes, 20 participaram de um TMR, utilizando o ajuste da sensibilidade do respirador e compuseram o grupo 2 (G-1) (9M e 11H), 5 pacientes participaram do TMR com uso do theshold, constituindo TMR foi utilizada uma carga de resistência inspiratória com 40 por cento a PImáx, obtida na avaliação inicial dos pacientes. Todos os pacientes participaram da rotina convencional do hospital e da UTI e foram sobmetidos a uma avaliação clínica constante realizada durante todo o período de internação. O protocolo constou de duas sessões ao dia, nas quais foram realizadas cinco séries de dez inspirações. Comparando os resultados dos três grupos, constatou-se que não houve diferenças significativas (p

Blood glucose responses in humans mirror lactate responses for individual anaerobic threshold and for lactate minimum in track tests.

The equilibrium point between blood lactate production and removal (La-(min)) and the individual anaerobic threshold (IAT) protocols have been used to evaluate exercise. During progressive exercise, blood lactate [La-]b, catecholamine and cortisol concentrations, show exponential increases at upper anaerobic threshold intensities. Since these hormones enhance blood glucose concentrations [Glc]b, this study investigated the [Glc] and [La-]b responses during incremental tests and the possibility of considering the individual glucose threshold (IGT) and glucose minimum (Glc(min)) in addition to IAT and La-(min) in evaluating exercise. A group of 15 male endurance runners ran in four tests on the track 3000 m run (v3km); IAT and IGT - 8 x 800 m runs at velocities between 84% and 102% of v3km; La-(min) and Glc(min) - after lactic acidosis induced by a 500-m sprint, the subjects ran 6 x 800 m at intensities between 87% and 97% of v3km; endurance test (ET) - 30 min at the velocity of IAT. Capillary blood (25 microl) was collected for [La-]b and [Glc]b measurements. The IAT and IGT were determined by [La-]b and [Glc]b kinetics during the second test. The La-(min) and Glc(min) were determined considering the lowest [La-] and [Glc]b during the third test. No differences were observed (P < 0.05) and high correlations were obtained between the velocities at IAT [283 (SD 19) and IGT 281 (SD 21) m. x min(-1); r = 0.096; P < 0.001] and between La-(min) [285 (SD 21)] and Glc(min) [287 (SD 20) m. x min(-1) r = 0.77; P < 0.05]. During ET, the [La-]b reached 5.0 (SD 1.1) and 5.3 (SD 1.0) mmol x l(-1) at 20 and 30 min, respectively (P > 0.05). We concluded that for these subjects it was possible to evaluate the aerobic capacity by IGT and Glc(min) as well as by IAT and La-(min).