Comparison between anaerobic threshold determined by ventilatory variables and blood lactate response in cyclists

Abstracts

Muitas investigações têm demonstrado que a coincidência entre os limiares ventilatórios e os limiares que se utilizam da resposta do lactato nem sempre ocorre, sugerindo que não existe relação entre causa e efeito entre os fenômenos. Dessa forma, o presente estudo teve como objetivos comparar e correlacionar os valores de consumo de oxigênio (VO2), potência (W) e freqüência cardíaca (FC) obtidos por protocolos de determinação do limiar ventilatório (LV) e limiar anaeróbio individual (IAT). A amostra foi constituída por oito ciclistas de níveis paulista e nacional (idade: 27,88 ± 8,77 anos; massa corporal: 65,19 ± 4,40kg; estatura: 169,31 ± 5,77cm). O IAT foi determinado iniciando-se com aquecimento de três minutos a 50W com aumentos progressivos de 50W.3min-1 até a exaustão voluntária, com as coletas de sangue aos 20 segundos finais de cada estágio e durante a recuperação. Para a determinação do LV, utilizou-se o mesmo protocolo adotado para a determinação do IAT, porém, sem efetuar as coletas de sangue. O LV foi identificado pelas mudanças da ventilação pulmonar e dos equivalentes ventilatórios de O2 e CO2. O teste t de Student não revelou diferenças estatisticamente significantes em nenhuma das variáveis obtidas. As associações encontradas foram altas e significativas. O VO2 (ml.kg-1.min-1), P (W) e FC (bpm) correspondente ao LV e IAT, e as associações entre as variáveis foram, respectivamente, de: 48,00 ± 3,82 vs 48,08 ± 3,71 (r = 0,90); 256,25 ± 32,04 vs 246,88 ± 33,91 (r = 0,84); 173,75 ± 9,18 vs 171,25 ± 12,02 (r = 0,97). De acordo com os resultados obtidos, pode-se concluir que o IAT e o LV produzem valores semelhantes de VO2, W e FC, o que favorece a adoção do LV por ser um método não-invasivo para determinação do limiar anaeróbio em ciclistas.

Limiar anaeróbio; Resposta do lactato sanguíneo; Ciclistas

ORIGINAL ARTICLE

Comparison between anaerobic threshold determined by ventilatory variables and blood lactate response in cyclists

Comparación entre umbral anaeróbico determinado por variables ventilatórias y por la respuesta del lactato sanguíneo en ciclistas

Alexandre Hideki Okano^{I, II, IV}; Leandro Ricardo Altimari^{I, IV}; Herbert Gustavo Simões^V; Antonio Carlos de Moraes^{I, IV}; Fábio Yuzo Nakamura^{I, II, III}; Edilson Serpeloni Cyrino^{I, II, III}; Roberto Carlos Burini^VI

^IGEPEMENE Group of Study and Research in Metabolism, Nutrition and Exercise – CEFD/UEL

^IIGroup of Studies on Physiological Adaptations to the Training – CEFD UEL

^IIICenter of Physical Education and Sports – CEFD – Londrina State University – UEL

^IVSchool of Physical Education, Campinas State University – Unicamp

^VDepartment of Physical Education, Brasilia Catholic University

^VICenter of Metabolism in Exercise and Nutrition, FM.UNESP/Botucatu

^{Correspondence to}

ABSTRACT

Many investigations have shown that the coincidence between the ventilatory thresholds and those thresholds using the lactate response does not happen all of the time, suggesting that there is no relationship between the cause-effect between these phenomena. Thus, the present study had as main purpose to compare and correlate the Oxygen consumption (VO₂), the power (W), and the heart rate (HR) values attained using protocols to determine the Ventilatory Threshold (VT) and the Individual Anaerobic Threshold (IAT). The sampling was constituted by eight State and National level cyclists (age: 27.88 ± 8.77 years; body mass: 65.19 ± 4.40 kg; height: 169.31 ± 5,77 cm). The IAT was determined starting from a three minutes 50 W warm up with progressive increases of 50 W.3min^-1 up to achieving the voluntary exhaustion, when the blood was collected in the last 20 seconds of each phase, and during the recovering period. In order to determine the VT, it was used the same protocol used to determine the IAT, but without performing the blood collection. The VT was identified through the changes in the pulmonary ventilation, as well as of the ventilatory equivalent of the O₂ and CO₂. The t-Student test showed no significant statistical difference in any of the attained variables. The associations found were high and significant. The VO₂ (ml.kg^-1.min.^-1), P (W), and HR (bpm) corresponding to the VT and IAT, as well as the associations between variables were respectively: 48.00 ± 3.82 vs. 48.08 ± 3.71 (r = 0.90); 256.25 ± 32.04 vs. 246.88 ± 33.91 (r = 0.84); 173.75 ± 9.18 vs. 171.25 ± 12.02 (r = 0.97). According to the results attained, it can be concluded that the IAT and the VT produce similar VO₂, W, and HR values, favoring the adoption of the VT because it is a non-invasive method to determine the anaerobic threshold in cyclists.

Keywords: Anaerobic threshold. Blood lactate response. Cyclists.

RESUMEN

Muchas investigaciones han estado demostrando que la coincidencia entre los umbrales ventilatorios y los umbrales que se usan en la respuesta del lactato ni siempre ocurre, mientras que también se sugiere que no existe una relación causa-efecto entre estos fenómenos. De esta manera, el estudio presente tiene como objetivos comparar y poner en correlación los valores de consumo de oxígeno (VO₂), potencia (W) y frecuencia cardíaca (FC) obtenidos por los protocolos de determinación del umbral ventilatorio (UV) y el umbral anaeróbico individual (UAI). La muestra se constituyó de ocho ciclistas de nivel de paulistas y nacionales (de edad: 27,88 ± 8,77 años; de masa corpórea: 65,19 ± 4,40 kg; de estatura: 169,31 ± 5,77 centímetros). UAI fue al principio determinado con un calentamiento de tres minutos a 50 W con aumentos progresivos de 50W.3min-1 hasta el agotamiento voluntario, con colecta de sangre a los 20 segundos finales de cada fase y durante la recuperación. Para la determinación de UV, el mismo protocolo se usó adoptando para la determinación de UAI, sin embargo, sin hacer esta vez las colectas de sangre. UV se identificó por los cambios del ventilación pulmonar y de los equivalentes ventilatórios de O₂ y CO₂. La prueba t de Student no reveló las diferencias estadisticamente significativas en ninguna de las variables obtenidas. Las asociaciones encontradas eran altas y significantes. VO₂ (ml.kg-1.min-1), P (W) y FC (el bpm) correspondiendo a UV y UAI, y las asociaciones entre las variables eran, respectivamente de: 48,00 ± 3,82 contra 48,08 ± 3,71 (el r = 0,90); 256,25 ± 32,04 contra 246,88 ± 33,91 (el r = 0,84); 173,75 ± 9,18 contra 171,25 ± 12,02 (el r = 0,97). De acuerdo con los resultados obtenidos, puede concluirse que UAI y UV producen valores similares de VO₂, W y FC, lo que favorece la adopción de UV como un método no-invasivo para la determinación del umbral anaerobio en ciclistas.

Palabras-clave: Umbral anaerobio. Respuesta del lactato sanguíneo. Ciclismo.

INTRODUCTION

In the last decades, the metabolic thresholds have been the target of several investigations within the exercise physiology, and they are considered extremely relevant parameters, more important than the maximal oxygen consumption to prescribe the training intensity^(1-3), to control the effects of the training^(4,5), and to predict the physical performance^(6-8).

The term Anaerobic Threshold (AnT) was introduced by Wasserman and McIlroy⁽⁹⁾, and it is defined as the strength intensity anterior to the exponential increase factor of the blood lactate compared to the resting levels. Later, it was verified that there are two thresholds, and this has originated the term "aerobic-anaerobic transition" introduced by Kindermann et al.⁽²⁾. The first transition point is identified as Aerobic Threshold (AeT) that reflects the exercise intensity corresponding to the beginning of the blood lactate accumulation. The second transition point would be called the AnT, and it represents the exercise intensity corresponding to the maximal steady state of the blood lactate (MSSL)⁽¹⁰⁾. The authors suggest that the fist transition corresponds to the AnT proposed by Wasserman and McIlroy⁽⁹⁾, or the Ventilatory Threshold (VT₁)⁽¹¹⁾. The second transition point is considered the breathing compensatory point⁽⁹⁾, or the Ventilatory Threshold 2 (VT₂)⁽¹¹⁾. These different terminologies for correlate phenomena have been caused some confusion in the area of the exercise physiology. In order to determine the intensities corresponding to the AeT and the AnT, Kinderman et al.⁽²⁾ adopted fixed concentrations of 2 and 4 mmol.1^-1 of the blood lactate, respectively, in an incremental exercise protocol.

The majority of the researchers use fixed 4 mmol.1^-1 blood lactate concentrations to determine the MSSL, and they have proposed several terminologies to identify such phenomenon^(2,12-15).

Heck et al.⁽¹⁰⁾ justify the option for that fixed blood lactate concentration (4 mmol.1^-1) as the majority of individuals presents such exercise intensity, the maximal ability to remove the produced lactate. Nevertheless, in that same study, it was verified that the MSSL can occur in blood lactate concentrations within a 3.1 and 5.54 mmol.1^-1 range.

Similar results have been verified by Stegmann et al.⁽¹⁶⁾, who found different individual values of the blood lactate upon the identification of the MSSL in an incremental test in which they varied between 1.4 and 7.5 mmol.1^-1. Having in mind the high inter-individual variability found in the results, the authors introduced the term Individual Anaerobic Threshold (IAT), which is an identifying method for the MSSL that does not respect the fixed lactate concentration, and it may be employed on running, cycle ergometer, rowgonometer, as well as for performance assessment, training prescription and control^(3,4,17-25).

Several researchers have investigated the relationship between the IAT and other protocols aiming to identify the MSSL, but in those studies, the blood lactate response was determined using the direct method^{(20,22,23,26)}. The determination of the blood lactate response by means of the direct method requires a scheduled blood collection, thus, it is necessary to use non-invasive methods to identify that phenomenon.

Some studies involving non-invasive methods to determine the IAT have been developed. Nevertheless, it was found no coincidence in the exercise intensity attained by the IAT compared to the critic power⁽¹⁹⁾ and the deflection point of the heart rate proposed by Conconi⁽²⁷⁾.

The non-invasive method that allows identify the MSSL during the incremental load exercise, involves the VT estimate. Nevertheless, the VT and the thresholds coincidence using lactate does not occur all the time, suggesting that there is no cause-effect relationship between these phenomena. The findings from studies that have analyzed the relationship between the IAT and the VT are quite controversal^(11,28,29).

Based on these facts, the purposes of the present study were: to set comparisons between the Oxygen consumption (VO₂), the intensity (W), and the heart rate (HR) values during the accomplishment of the protocols to determine the IAT and the VT in cycling athletes, and later, to verify the possible associations between parameters attained by both methods.

METHODS

Subjects

It participated in this study eight male cycling athletes at the state and national levels competing in the Bike Speed (n = 4) and Mountain Bike (n = 4) categories. The general characteristics of the sampling are presented on table 1. As pre-requirements to be admitted in the trial, athletes should have at least two years experience in regional or state competitions. After being examined by a physician, every individual received information on the goals of the study and the procedures which they would be submitted to, and they signed a free clarified consent. The study was developed at the CeMENutri (Center of Metabolism in Exercise and Nutrition), and it was approved by the Ethics Committee in Research of the Botucatu School of Medicine/UNESP, SP.

Dietetic control

Aiming to avoid the trial would suffer any kind of interference in the test results as to the energetic substrate availability^(30,31), athletes had a nutritional follow-up along the whole study.

From the application of a food questionnaire (recalling 24 hours of their food habits), the nutritionists team elaborated ordinary diet schedules as to the food habits of the assessed individuals. They were instructed to follow such diet along the whole period of the trial. Furthermore, it was elaborated a standard breakfast to be consumed two hours before the test accomplishment. Also, all individuals were instructed to avoid the intake of caffeinated products 24 hours before the tests, as those substances could influence the results⁽³²⁾. The information on the quantity and quality of the consumed foods was processed by means of the Virtual Nutri version 1.0 nutritional analysis software.

Experimental outlining

In the first step of the trial, individuals came to the laboratory to have their medical examination and anthropometric measurements, in order to characterize the sampling, and to have an interview with the nutritionists, when they received the food intake guidelines to be followed along the whole period of the trial. Furthermore, it was scheduled a timetable for each athlete to come to the laboratory in the next phase of the trial. Later, all individuals performed a pre-trial test with the purpose to familiarize them to the equipment and the protocol.

From the second step of the trial on, the individuals came to the laboratory in predefined hours, when they were submitted to the test to determine the IAT and the VT₂, which were randomly performed. All the tests (pre-trial, IAT, and VT₂) were applied with a 72 hours interval between them. Individuals were instructed not to perform their physical activities 24 hours prior to the accomplishment of each test, in order to avoid any interference.

Ergospirometry

The incremental tests were performed in an electromagnetic ergonometric cycle (Corival 400, Quinton^®, USA). The ventilatory variables were continuously measured in an open circuit ergo-spirometric system (QMC^TM 90 Metabolic Cart, Quinton^®, Bothell, USA) using the breath-by-breath technique. At the beginning of each test, the gauging was performed through a Hans Rudolf 5530 3-liters calibration syringe and a mix of 26% O₂ gas with a N₂ and 4% CO₂ and 16% O₂ balance (White Martins Praxair, Inc. São Paulo, Brazil).

The analysis was processed on an IBM computer through the calculations of the minute ventilation (VE), the VO₂, the carbon dioxide production (VCO₂), and the relationship between the carbon dioxide production and the oxygen consumption (R).

The HR was measured through a cardiofrequencymeter (Vantage NV, Polar Electro OY, Finland) with an every 5 seconds record, uploading on a software (Polar Precision Performance^TM, Finland) for later analysis. The HR corresponding to different loads was determined from the recorded values of the last five seconds of each phase. The variables of the environmental temperature and the relative air humidity were kept between 21 and 24ºC, and 40 and 60%, respectively.

IAT

To determine the IAT, initially, the individuals performed a three minute warm up at a 50 W load, and next, the incremental test started with a 50 W increase to the load every three minutes, keeping the 70 revolution per minute cadency. During the incremental test, the individuals were verbally encouraged to go on up to the voluntary exhaustion. The blood collection was performed in the ear lobule on a resting condition (pre-strength) in the final 20 seconds of each load up to the exhaustion, and at three, five and ten minutes after the test finished.

From the construction of a graphic representing the blood lactate values in each phase of the incremental test and during the passive recovering (figure 1), the IAT was determined following the procedures proposed by Stegmann et al.⁽¹⁶⁾.

VT₂

The VT was identified through the application of the same protocol used to determine the IAT, but in this situation, the blood collection was not performed. The VT₂, or breathing compensatory point, had a double identification through the use of the ventilatory equivalent of the Oxygen (VE/VO₂), the ventilatory equivalent of the carbon dioxide (VE/VCO₂) considering the sudden increase in the VE/VCO₂ according to the criteria proposed by McLellan⁽¹¹⁾. Figure 2 illustrates the identification of the thresholds; nevertheless, it was performed in this study only the VT₂.

Biochemical analysis

It was collected 25 µl of the ear lobule blood through a previously gauged heparinized glass capillary, and they were immediately transferred to a 1.5 ml "Ependorf" type polyethylene microtubules containing 50 µl of a 1% sodium fluoride solution. Next, the samples were stored at –70ºC. The lactate analysis was performed using an electroenzimatic analyzer (YSL 2300 STAT Yellow Spring Co., USA), and the values were expressed in mmol.l^-1.

Statistical treatment

The results were gathered according to the mean values and standard deviation using the statistical package Statistica 6.0^® (STATSOFT INC., USA). Upon the application of the Shapiro Wilk test, it was verified that the data distribution were normal. Thus, the variables attained in the protocols contrasted from the t-Student test for dependent sampling. The linear Pearson correlation coefficient was employed to verify the associations between the variables attained in the protocols, in order to determine the IAT and the VT₂. The significance level adopted for every analysis was 1%.

RESULTS

Table 1 presents the general features of the sampling.

Table 2 presents the values for the VO₂max, the intensity at the moment of the exhaustion (WVO₂max), and the FCmax attained in both protocols used in this study (IAT and VT₂). It was found no significant differences compared to the above described variables at the exhaustion moment for the IAT and VT₂ tests. On that same table, it can be observed the blood lactate values at the intensity corresponding to the IAT and the maximal load.

The results of the VO₂, W and HR corresponding to the VT₂ and the IAT are presented on table 3. The t-Student test did not identify significant differences between the VO₂, W and HR values attained in the VT₂ and IAT protocols.

The linear regression between the VO₂, the HR and W attained in both methods are presented in figures 3, 4 and 5, respectively. The associations were high and significant in every analyzed variable.

DISCUSSION

The IAT is defined as the higher metabolic rate where the blood lactate concentration is kept in a balanced state during prolonged exercises, and the elimination of the blood lactate is maximal, being equivalent to the diffusion rate of the muscular compartment to the blood⁽¹⁶⁾. Therefore, it might be considered that the IAT protocol is capable to determine the intensity corresponding to the MSSL.

In such sense, several studies have found the MSSL during the long endurance rectangular test at the intensity corresponding to the IAT, making such relationship evident^{(4,20,23,26,33)}.

Unlike the fixed concentration threshold of 4 mmol.1^-1 of the blood lactate, the IAT protocol considers the behavior of the individual lactate upon the occurrence of the second aerobic-anaerobic transition point during a progressive load test. In the present study, the blood lactate concentration corresponding to the IAT was a mean of 3.44 mmol.1^-1, presenting a 1.9 to 5.04 mmol.1^-1 inter-individual variation. These results confirm what was found by Stegmann et al.⁽¹⁶⁾ and Stegmann and Kindermann⁽²⁶⁾, who found a 1.4-7.5 and 1.8-6.1 mmol.1^-1 variation in the blood lactate, respectively.

Related to the VT₂, the literature has pointed out that the variable, as well as the IAT can be considered a MSSL indicator^(34-36). Thus, theoretically, the intensities attained in the protocols to determine the IAT and the VT₂ should be coincident. The findings of the present study confirm this hypothesis. Although the VT₂'s intensity is 3.8% higher compared to the IAT, that difference was not statistically significant. Furthermore, the coefficients of the correlation between the variables attained by both methods were r = 0.84 to r = 0.97. These results suggest that whenever the aim is to classify the individuals as to their aerobic ability, it seems there is no interference from the protocol used.

Several studies have evidenced the close relationship between the AnT determined by fixed concentrations of the blood lactate and by the ventilatory method^(35,37-39). However, few studies have analyzed the direct relationship between the IAT and the ventilatory thresholds^(11,28,29).

In a sampling with non-trained individuals, McLellan⁽¹¹⁾ compared the VT₂, the IAT and the AnT corresponding to 4 mmol.1^-1 attained in the protocols ministered at the cycle ergometer. The criterion adopted to identify the VT was the change in the response pattern of the VE/VCO₂ response above the VR₁. The author verified that the IAT values were statistically lower than those observed in the other methods.

Dickhuth et al.⁽²⁸⁾, employing incremental tests on the treadmill have analyzed the relationship between the reproducibility of the IAT intensities and the VT determined through the V-Slope method (VT_V-Slope). The authors found a high correlation (r = 0.97; p < 0.01), and the IAT was 7-8% higher than the VT values.

McNaughton et al.⁽²⁹⁾ compared several methods to determine the AnT, and after that, they submitted the individuals to a continuous test up to achieving the voluntary exhaustion at the intensity attained by each method. The VT_V-Slope intensity surpassed in 13% the values found in the IAT. However, these differences were not statistically significant. Using the VT intensity, the individuals succeeded in remaining 14 minutes at the submaximal test. When they worked out at the IAT intensity, the time spent in the test practically doubled, attaining around 28 minutes. These findings indicate it is required a judicious analysis of the meaning of each threshold, mainly when the purpose is to prescribe the training.

Added to the fact there is a reduced amount of studies developed aiming to compare the IAT and the ventilatory thresholds, the results are quite conflicting. Possibly, the discrepancy in the findings can be related to the criteria adopted to determine the ventilatory thresholds, the characteristics of the individuals assessed, or even to the use of different kinds of exercises and/or protocols (load increment intensity and endurance of the phases).

Initially, the criteria adopted to identify the ventilatory thresholds were the breaking points of the VE related to the VO₂. Later, besides the previously mentioned criterion, it was suggested the use of other variables, such as VE/VO₂, VE/VCO₂, and R^(40,41). Basically, the aim was to identify an incremental load protocol when there is an increase in the VE/VO₂, and the O₂ pressure with no alterations on the VE/VCO₂ and on the CO₂ pressure. To some authors, such intensity corresponds to the VT₁⁽¹¹⁾. From this point on, the increase in the exercise intensity will cause a metabolic acidosis, resulting in a decrease in the pH, and consequently an increase on the VE/VCO₂ and on the CO₂. That second point is considered the VT₂⁽¹¹⁾, or the respiratory compensatory point.

Related to the individual's physical condition, the mechanisms involved in the occurrence of the AnT seem to be the same both in athletes and in non-trained individuals. However, the point where the phenomenon occurs is different among them (Wyatt, 1999).

This can be explained in function of the variation in the diffusion ability and/or removal of the lactate produced between different portions⁽⁴²⁾.

Another important aspect that cannot be disregarded is the protocol adopted to determine the ventilatory thresholds. The optimum protocol is the one that allows the researcher to observe the inflexion point of the EV/VO₂ and the region of the isocapneic tamponage (increase in the EV/VO₂ with no modifications in the EV/CVO₂). Thus, Davis⁽⁴³⁾ suggests the use of incremental protocols constituted by one minute endurance phases. In this study, the protocol employed to determine the VT was similar to that adopted to identify the IAT, that means, three minutes endurance each phase. According to McLellan⁽¹¹⁾, that second threshold seems not to suffer any influence on the endurance of the phases (1, 3, or 5 minutes).

As it can be seen, there is a great amount of criteria and terminologies used to identify the metabolic thresholds. Thus, it is fundamental to make judicious observation of the protocol adopted to determine the blood lactate response, mainly aiming to prescribe the training intensity.

It is important to point out that one of the limitations of this study is related to the reduced sampling. In such sense, Stone et al.⁽⁴⁴⁾ recently pointed out that it is required to make a distinction between the concepts of Exercise Science and Sports Science.

Generally, the literature has several publications related to the Exercise Science. Nevertheless, there is a scarcity of publications related to the sports itself, that means, the Sport Science, understood as the one developed with the purpose to propitiate the sportive performance increment through the application of methods and scientific principles to the training assessment, controlling, and prescription⁽⁴⁴⁾.

CONCLUSION

Based on the results found in this study, it can be concluded that the protocols to determine the IAT and VT give similar VO₂, intensity and HR values, even presenting high correlations between these variables, favoring the adoption of the VT as this is a non-invasive method to determine the anaerobic threshold in cyclists.

All the authors declared there is not any potential conflict of interests regarding this article.

REFERENCES

Received in 3/8/04.

Final version received in 25/7/05.

Approved in 5/9/05.

• 1. Jacobs I. Blood lactate. Implications for training and sports performance. Sports Med 1986;3:10-25.
• 2. Kindermann W, Simon G, Keul J. The significance of the aerobic-anaerobic transition for the determination of work load intensities during endurance training. Eur J Appl Physiol Occup Physiol 1979;42:25-34.
• 3. Meyer T, Gabriel HH, Kindermann W. Is determination of exercise intensities as percentages of VO2max or HRmax adequate? Med Sci Sports Exerc 1999;31: 1342-5.
• 4. Keith SP, Jacobs I, McLellan TM. Adaptations to training at the individual anaerobic threshold. Eur J Appl Physiol Occup Physiol 1992;65:316-23.
• 5. Gaskill SE, Walker AJ, Serfass RA, Bouchard C, Gagnon J, Rao DC, et al. Changes in ventilatory threshold with exercise training in a sedentary population: the Heritage Family Study. Int J Sports Med 2001;22:586-92.
• 6. Coyle EF. Integration of the physiological factors determining endurance performance ability. Exerc Sport Sci Rev 1995;23:25-63.
• 7. Coyle EF, Feltner ME, Kautz SA, Hamilton MT, Montain SJ, Baylor AM, et al. Physiological and biomechanical factors associated with elite endurance cycling performance. Med Sci Sports Exerc 1991;23:93-107.
• 8. Roecker K, Schotte O, Niess AM, Horstmann T, Dickhuth HH. Predicting competition performance in long-distance running by means of a treadmill test. Med Sci Sports Exerc 1998;30:1552-7.
• 9. Wasserman K, McIlroy MB. Detecting the threshold of anaerobic metabolism in cardiac patients during exercise. Am J Cardiol 1964;14:844-52.
• 10. Heck H, Mader A, Hess G, Mucke S, Muller R, Hollmann W. Justification of the 4-mmol/l lactate threshold. Int J Sports Med 1985;6:117-30.
• 11. McLellan TM. Ventilatory and plasma lactate response with different exercise protocols: a comparison of methods. Int J Sports Med 1985;6:30-5.
• 12. Mader A, Liesen H, Heck H, Philippi H, Schürch PM, Hollmann W. Zur beurteilung der sportartspezifischen Ausdauerleinstungsfähigkeit im Labor. Sportarzt Sportmed 1976;26:109-12.
• 13. Mader A, Liesen H, Heck H, Philippi H, Schürch PM, Hollmann W. Zur beurteilung der sportartspezifischen Ausdauerleinstungsfähigkeit im Labor. Sportarzt Sportmed 1976;24:80-8.
• 14. Sjodin B, Jacobs I. Onset of blood lactate accumulation and marathon running performance. Int J Sports Med 1981;2:23-6.
• 15. Hollmann W. Historical remarks on the development of the aerobic-anaerobic threshold up to 1966. Int J Sports Med 1985;6:109-16.
• 16. Stegmann H, Kindermann W, Schnabel A. Lactate kinetics and individual anaerobic threshold. Int J Sports Med 1981;2:160-5.
• 17. Coen B, Schwarz L, Urhausen A, Kindermann W. Control of training in middle- and long-distance running by means of the individual anaerobic threshold. Int J Sports Med 1991;12:519-24.
• 18. McLellan TM, Cheung KS, Jacobs I. Incremental test protocol, recovery mode and the individual anaerobic threshold. Int J Sports Med 1991;12:190-5.
• 19. McLellan TM, Cheung KS. A comparative evaluation of the individual anaerobic threshold and the critical power. Med Sci Sports Exerc 1992;24:543-50.
• 20. Urhausen A, Coen B, Weiler B, Kindermann W. Individual anaerobic threshold and maximum lactate steady state. Int J Sports Med 1993;14:134-9.
• 21. Urhausen A, Weiler B, Coen B, Kindermann W. Plasma catecholamines during endurance exercise of different intensities as related to the individual anaerobic threshold. Eur J Appl Physiol Occup Physiol 1994;69:16-20.
• 22. Beneke R. Anaerobic threshold, individual anaerobic threshold, and maximal lactate steady state in rowing. Med Sci Sports Exerc 1995;27:863-7.
• 23. Bourgois J, Vrijens J. Metabolic and cardiorespiratory responses in young oarsmen during prolonged exercise tests on a rowing ergometer at power outputs corresponding to two concepts of anaerobic threshold. Eur J Appl Physiol Occup Physiol 1998;77:164-9.
• 24. Baldari C, Guidetti L. A simple method for individual anaerobic threshold as predictor of max lactate steady state. Med Sci Sports Exerc 2000;32:1798-802.
• 25. Guidetti L, Musulin A, Baldari C. Physiological factors in middleweight boxing performance. J Sports Med Phys Fitness 2002;42:309-14.
• 26. Stegmann H, Kindermann W. Comparison of prolonged exercise tests at the individual anaerobic threshold and the fixed anaerobic threshold of 4 mmol.l(-1) lactate. Int J Sports Med 1982;3:105-10.
• 27. Bourgois J, Vrijens J. The Conconi test: a controversial concept for the determination of the anaerobic threshold in young rowers. Int J Sports Med 1998;19: 553-9.
• 28. Dickhuth HH, Yin L, Niess A, Rocker K, Mayer F, Heitkamp HC, et al. Ventilatory, lactate-derived and catecholamine thresholds during incremental treadmill running: relationship and reproducibility. Int J Sports Med 1999;20:122-7.
• 29. McNaughton L, Wakefield G, Fasset R, Bentley D. A comparison of lactate kinetics, minute ventilation and acid-base balance as measure of the anaerobic threshold. Journal of Human Moviment Studies 2001;41:247-61.
• 30. Hughes EF, Turner SC, Brooks GA. Effects of glycogen depletion and pedaling speed on "anaerobic threshold". J Appl Physiol 1982;52:1598-607.
• 31. Yoshida T. Effect of dietary modifications on lactate threshold and onset of blood lactate accumulation during incremental exercise. Eur J Appl Physiol Occup Physiol 1984;53:200-5.
• 32. Berry MJ, Stoneman JV, Weyrich AS, Burney B. Dissociation of the ventilatory and lactate thresholds following caffeine ingestion. Med Sci Sports Exerc 1991; 23:463-9.
• 33. McLellan TM, Jacobs I. Active recovery, endurance training, and the calculation of the individual anaerobic threshold. Med Sci Sports Exerc 1989;21:586-92.
• 34. Aunola S, Rusko H. Does anaerobic threshold correlate with maximal lactate steady-state? J Sports Sci 1992;10:309-23.
• 35. Ribeiro JP, Hughes V, Fielding RA, Holden W, Evans W, Knuttgen HG. Metabolic and ventilatory responses to steady state exercise relative to lactate thresholds. Eur J Appl Physiol Occup Physiol 1986;55:215-21.
• 36. Yamamoto Y, Miyashita M, Hughson RL, Tamura S, Shinohara M, Mutoh Y. The ventilatory threshold gives maximal lactate steady state. Eur J Appl Physiol Occup Physiol 1991;63:55-9.
• 37. Wyatt FB. Comparison of lactate and ventilatory threshold to maximal oxygen consumption: a meta analysis. Journal of Strength and Conditioning Research 1999;13:67-71.
• 38. Ahmaidi S, Hardy JM, Varray A, Collomp K, Mercier J, Prefaut C. Respiratory gas exchange indices used to detect the blood lactate accumulation threshold during an incremental exercise test in young athletes. Eur J Appl Physiol Occup Physiol 1993;66:31-6.
• 39. Dickstein K, Barvik S, Aarsland T, Snapinn S, Karlsson J. A comparison of methodologies in detection of the anaerobic threshold. Circulation 1990;81:II38-46.
• 40. Davis JA, Frank MH, Whipp BJ, Wasserman K. Anaerobic threshold alterations caused by endurance training in middle-aged men. J Appl Physiol 1979;46:1039-46.
• 41. Beaver WL, Wasserman K, Whipp BJ. A new method for detecting anaerobic threshold by gas exchange. J Appl Physiol 1986;60:2020-7.
• 42. Simon J, Young JL, Blood DK, Segal KR, Case RB, Gutin B. Plasma lactate and ventilation thresholds in trained and untrained cyclists. J Appl Physiol 1986;60: 777-81.
• 43. Davis JA. Anaerobic threshold: review of the concept and directions for future research. Med Sci Sports Exerc 1985;17:6-21.
• 44. Stone MH, Sands WA, Stone ME. The downfall of sports science in the United States. Strength Cond J 2004; 26:72-5.

Publication Dates

• Publication in this collection
  02 May 2007
• Date of issue
  Feb 2006

History

• Reviewed
  25 July 2005
• Received
  03 Aug 2004
• Accepted
  05 Sept 2005