Evaluation of maximal lactate steady state in middle-aged hypertensive women

Abstract AIM The aim of this study was to investigate the lactate response in physically inactive hypertensive women submitted to the treadmill maximal lactate steady state (MLSS) protocol. METHODS Twenty-two hypertensive women (40 - 64 years) performed a familiarization period of walking on the treadmill following by one incremental test for estimating the initial workload for exercise testing. MLSS protocol was composed by walking in a treadmill during thirty minutes with fixed velocity in 5.5 km/h. Incline was used for determination of the intensity of each volunteer. Blood samples were collected from the ear lobe in the rest period, minute 10th and at the end of the test (minute 30th or at exhaustion time point) for lactate analysis. RESULTS Hypertensive women showed a lower lactate concentration at MLSS (3.25 ± 0.81 mmol/L) as compared with data obtained in the literature (4 mmol/L), approximately 18.8%. Neither inclines nor age affected MLSS parameters in the population. A positive and strong correlation was found between incline and MLSS, as well as incline and lactate level at minute 30th, even when adjusted by age factor. CONCLUSION Physically inactive hypertensive women show a lower MLSS than the average established in the literature but within the range of variations previously reported. Furthermore, a higher MLSS incline correlates positive and directly with higher lactate concentrations for the same aerobic capacity regardless of age.

Comparison of maximal lactate steady state with V2, V4, individual anaerobic threshold and lactate minimum speed in horses / Comparação da máxima fase estável do lactato com a V2, V4, o limiar anaeróbio individual e lactato mínimo em equinos

The anaerobic threshold is a physiologic event studied in various species. There are various methods for its assessment, recognized in the human and equine exercise physiology literature, several of these involving the relationship between blood lactate concentration (LAC) and exercise load, measured in a standardized exercise test. The aim of this study was to compare four of these methods: V2, V4, individual anaerobic threshold (IAT) and lactate minimum speed (LMS) with the method recognized as the gold standard for the assessment of anaerobic threshold, maximal lactate steady-state (MLSS). The five tests were carried out in thirteen trained Arabian horses, in which velocities and associated LAC could be measured. The mean velocities and the LAC associated with the anaerobic threshold for the five methods were respectively: V2 = 9.67±0.54; V4 = 10.98±0.47; V IAT = 9.81±0.72; V LMS = 7.50±0.57 and V MLSS = 6.14±0.45m.s-1 and LAC IAT = 2.17±0.93; LAC LMS = 1.17±0.62 and LAC MLSS = 0.84±0.21mmol.L-1. None of the velocities were statistically equivalent to V MLSS (P<0.05). V2, V4 and V LMS showed a good correlation with V MLSS , respectively: r = 0.74; r = 0.78 and r = 0.83, and V IAT did not significantly correlate with V MLSS. Concordance between the protocols was relatively poor, i.e., 3.28±1.00, 4.84±0.30 and 1.43±0.32m.s-1 in terms of bias and 95% agreement limits for V2, V4 and LMS methods when compared to MLSS. Only LAC LMS did not differ statistically from LAC MLSS. Various authors have reported the possibility of the assessment of anaerobic threshold using rapid protocols such as V4 and LMS for humans and horses. This study corroborates the use of these tests, but reveals that adjustments in the protocols are necessary to obtain a better concordance between the tests and the MLSS.

O limiar anaeróbio é um evento fisiológico estudado em várias espécies. Sua mensuração possui vários métodos reconhecidos na literatura da fisiologia do exercício humano e equino, muitos deles envolvendo a relação entre a concentração sanguínea de lactato (LAC) e a carga de exercício. O objetivo do presente estudo foi comparar quatro desses métodos: V2 , V4 , limiar anaeróbio individual (LAI) e o teste do lactato mínino (LM) com o método reconhecido na literatura como o padrão ouro para a mensuração do limiar anaeróbio, a máxima fase estável do lactato (MFEL). Os cinco testes foram realizados em treze equinos árabes treinados, nos quais as velocidades e suas respectivas LAC puderam ser quantificadas. As velocidades médias e LAC associadas ao limiar anaeróbio aferido pelos cinco métodos foram respectivamente: V2 = 9,67±0,54; V4 = 10,98±0,47; V LAI = 9.81±0.72; V LM = 7,50±0,57 e V MFEL = 6,14±0,45m.s-1 ; e LAC LAI = 2,17±0,93; LAC LM = 1,17±0,62 e LAC MFEL = 0,84±0,21mmol.L-1. Nenhuma dessas velocidades foi estatisticamente igual à V MFEL (P<0,05). A V2 , a V4 e a V LM mostraram uma boa correlação com a V MFEL , respectivamente r = 0,74; r = 0,78 e r = 0,83, e a V LAI não se correlacionou significativamente com a V MFEL. A concordância entre os protocolos foi relativamente fraca, sendo 3,28±1,00; 4,84±0,30 e 1,43±0,32m.s-1 em termos de viés e limites de concordância a 95% para os métodos V2 , V4 e LM comparados à MFEL. Muitos autores relataram a possibilidade da mensuração do limiar anaeróbio pelo uso de protocolos rápidos, como a V4 e o LM, para humanos e equinos. O presente estudo corrobora a utilização desses testes, mas revela que ajustes nos protocolos são necessários para se obter uma melhor concordância entre os mesmos e a MFEL.

Non-exhaustive test for aerobic capacity determination in running rats.

A simple and applicable method for non-exhaustive aerobic evaluation in running rats is described. Wistar rats were submitted to running test at different velocities (10, 15, 20, 25 m/min) with 48 h recovery among them. At each velocity, the rats ran two bouts of 5 min with 2 min of rest between bouts. Blood samples were collected at the end of each bout for lactate determination. For each intensity, delta lactate was calculated and using deltas obtained by four tests, an individual linear interpolation was plotted. The y-intercept of linear interpolation was the “null delta lactate” equivalent to the critical velocity (CV). To verify the lactate stabilization at CV, the animals were submitted to 25 min of continuous exercise (15, 20, 25 m/min), with blood collection every 5 min. The estimated CV was 16.6±0.7 m/min, with significant linear regressions (R=0.90±0.03). The rats presented maximal lactate steady state (MLSS) at 3.9±0.4 mmol/L, at 20 m/min. The CV was less than MLSS but significantly correlated with this parameter (r=0.78). This non-exhaustive test seems to be valid for the aerobic evaluation of sedentary rats and this protocol underestimates the MLSS in 20%. This test seems to be the interesting method for the evaluation of rats submitted to acute exercise or physical training.

Modelo de equilíbrio dinâmico: breve revisão da sua origem, implicações e novas perspectivas / Dynamic equilibrium model: review of its origin, approach and new projections

O Modelo de Equilíbrio Dinâmico (MED) assume a existência de uma intensidade máxima de exercício na qual seja possível observar um estado de equilíbrio fisiológico, o qual assegura o prolongamento do exercício. Até esta intensidade limite o exercício seria limitado pelos estoques de glicogênio muscular, mas acima desta, o acúmulo de metabólitos causaria a falha dos sistemas corporais e o término do exercício seria coincidente com o alcance de valores máximos em variáveis fisiológicas. Entretanto, o MED não se ajusta inteiramente aos resultados experimentais, pois estudos falharam em demonstrar um completo equilíbrio fisiológico em cargas iguais ou inferiores a esta intensidade limite. Adicionalmente, evidências mostram que nesta mesma faixa de intensidade, o término do exercício ocorre sem haver completa depleção nos estoques de glicogênio muscular. Inicialmente, o desalinhamento entre teoria e dados experimentais poderia ser devido, ao menos em parte, a um aspecto metodológico comum entre estudos anteriores: a ausência do término do exercício identificado na incapacidade da manutenção de uma potência mecânica requerida. A ausência do ponto de exaustão como critério do término do exercício pode ter gerado um artefato temporal nas medidas realizadas, não garantindo que cada medida temporal representasse a mesma fase de ajuste fisiológico ao exercício. Contudo estudos recentes do nosso grupo sugerem outra perspectiva para interpretação dos dados experimentais; a existência de equilíbrio fisiológico regulado pelos sistemas nervoso central e periférico, numa ampla faixa de intensidade de exercício.

The Dynamic Equilibrium Model (DEM) assumes the presence of a maximal exercise intensity at which a complete physiological steady state occurs, allowing the exercise to be prolonged. Up to this limit of intensity, the exercise would be limited by muscle glycogen storages, but above this the metabolic accumulation would lead to a bodily systems failure that would match with maximal values in physiological variables. However, the DEM does not agree with experimental results, because studies have failed to demonstrate a full physiological steady state during exercise at or below this limit of intensity. Additionally, evidences have shown that exercise terminates without complete muscle glycogen depletion within this intensity range. Initially, the disagreement between theory and experimental data could be due partially to a methodological aspect: the absence of exercise termination determined by the incapacity for maintaining a required power output. Such absence of an exhaustion point as criteria to establish the exercise termination could have caused a temporal artifact, not allowing that each temporal measure has indicated the same phase of physiological adjustment to the effort. Yet, recent findings of our group have suggested another perspective to interpret the experimental data; the existence of physiological steady state regulated by the central and peripheral nervous system within a broad exercise intensity range.

Determinação da potência mecânica no limite entre os domínios pesado/severo do crawl-atado / Measurement of mechanical power on the boundary of heavy/severe domain in the tethered-crawl

O objetivo deste estudo foi ajustar o modelo P-tLim à natação com o recurso do nado atado. Seu significado fisiológico para a descrição dos domínios pesado/severo foi obtido pelas relações com a velocidade crítica (VC), potência crítica (PC) e com máxima fase estável do lactato (MFEL). A velocidade correspondente a MFEL (vMFEL =1,17 ± 0,11 m/s) e a VC (1,19 ± 0,12 m/s) obtidas durante o nado desimpedido foram significantemente diferentes. Similarmente, a potência correspondente a MFEL (pMFEL = 89,2 ± 15,1 W) e a PC (99,4 ± 22,9 W) foram diferentes durante o nado atado. Não houve diferença da concentração de lactato na vMFEL (3,54 ± 0,9 mM) e pMFEL (3,76 ± 0,6 mM). Coeficientes de Pearson significativos (r > 0,70) foram observados entre os parâmetros vMFEL e pMFEL com seus respectivos pares do modelo tempo-limite. Assim, o nado atado parece ser válido para determinar os limites do domínio pesado/severo, podendo também ser utilizado para avaliar a capacidade aeróbia de nadadores.

The aim of this study was to access the P-tLim model in swimming, applying the load control available in full tethered swim condition. Its physiological meaning for the determination of boundary of heavy/severe domains was assessed from the relationships with critical velocity (CV), critical power (CP) and maximal lactate steady state (MLSS). The velocity at MLSS (vMLSS = 1.17 ± 0.11 m/s) and CV (1.19 ± 0.12 m/s) were significantly different. Similarly, the power at MLSS (pMFEL = 89.2 ± 15.1 W) and CP (99.4 ± 22.9 W) were significantly different. There was no difference between lactate concentration at vMLSS (3.54 ± 0.9 mM) and pMLSS (3.76 ± 0.6 mM). Significant Pearson’s coefficients (r > 0.70) were observed among vMLSS and PMLSS with their respective values on time-limited model. Thus, the tethered-crawl condition seems to be valid to determine the boundary of heavy/severe domains, and to access the aerobic capacity of swimmers.

Métodos de quantificação de carga de treinamento em exercício realizado no máximo estado estável de lactato / Methods of quantification of training load in exercise performed at maximal lactate steady state

O objetivo do presente estudo foi comparar e correlacionar as estimativas de impulso de treinamento (TRIMP) propostos por Banister (TRIMPBanister), Stagno (TRIMPStagno) e Manzi (TRIMPManzi). Os participantes foram submetidos a um teste progressivo em cicloergômetro, com registro da frequência cardíaca e da concentração de lactato sanguíneo. Em uma segunda ocasião, realizaram 30 min. de exercício na intensidade correspondente ao máximo estado estável de lactato, a partir do qual foram calculados o TRIMPBanister, TRIMPStagno e TRIMPManzi. Os valores médios de TRIMPBanister (56,5 ± 8,2 u.a.) e TRIMPStagno (51,2 ± 12,4 u.a.) não diferiram entre si (P > 0,05) e foram altamente correlacionados (r = 0,90), com boa concordância, ou seja, viés reduzido e limites de concordância relativamente estreitos. O TRIMPStagno e TRIMPManzi (73,4 ± 17,6 u.a.) apresentarem alta correlação (r = 0,93), mas com diferença significantes entre eles; ainda, se mostraram pouco concordantes. As estimativas de TRIMPBanister e TRIMPManzi não foram diferentes (P = 0,06) e apresentaram alta correlação (r = 0,82), com baixa concordância. Assim, conclui-se que os métodos de TRIMP não são equivalentes. Na prática, parece ser prudente monitorar o processo de treinamento assumindo apenas uma das estimativas.

The aim of the present study was to compare and correlate training impulse (TRIMP) estimates proposed by Banister (TRIMPBanister), Stagno (TRIMPStagno) and Manzi (TRIMPManzi). The subjects were submitted to an incremental test on cycle ergometer with heart rate and blood lactate concentration measurements. In the second occasion, they performed 30 min. of exercise at the intensity corresponding to maximal lactate steady state, and TRIMPBanister, TRIMPStagno and TRIMPManzi were calculated. The mean values of TRIMPBanister (56.5 ± 8.2 u.a.) and TRIMPStagno (51.2 ± 12.4 u.a.) were not different (P > 0.05) and were highly correlated (r = 0.90). Besides this, they presented a good agreement level, which means low bias and relatively narrow limits of agreement. On the other hand, despite highly correlated (r = 0.93), TRIMPStagno and TRIMPManzi (73.4 ± 17.6 u.a.) were different (P < 0.05), with low agreement level. The TRIMPBanister e TRIMPManzi estimates were not different (P = 0.06) and were highly correlated (r = 0.82), but showed low agreement level. Thus, we concluded that the investigated TRIMP methods are not equivalent. In practical terms, it seems prudent monitor the training process assuming only one of the estimates.