NON SPIROGRAPHIC OR NONINVASIVE METHODS TO ESTIMATE ANAEROBIC TRESHOLD

In the world of sports research, there are different ways to determinate physical conditioning, ranging from expensive laboratory-invasive methods to cheap, field based-non-invasive methods. The field based-non-invasive test maintains good reliability and low cost using physiological parameters such heart rate, saliva electrolytes or lactate, perceived exertion and electromyography among others. These parameters can be used to estimate anaerobic threshold (AnT) to predict sport performance, redirect training and can help coaches and athletes to be more competitive. However, each of this parameter has some particularities and controversy due to different results reported by specialist. These differences may be explained by protocol testing used, sport level sample, starting intensity or number of levels among others. Despite this, they still have good reproducibility and applications on field based test protocols. Mentioned tests could be used in a large scale, and more often, with paying attention about level of correlation with original invasive tests, and percent of possible mistake in estimation process. Cheaper, and simpler tests (instead subjective estimation of training load) allows using more precise planning and changing volume, and intensity of training, for coaches, and athletes, that have needed level of education and less money. Athletes comfort, and possible high frequency of testing during non invasive test, also must be emphasized as an advantage during training evaluation process.


INTRODUCTION
At least fifty years have passed since Wasserman and Mcllory (1964) developed the anaerobic threshold concept (AnT) which is defined as the lost between ventilator elements and workload within oxygen consumption and coincides with the upper limit of individual aerobic metabolism, besides this parameter relates to prolonged exercise performance (Davis, 1985; Ignjatović, Hofmann, & Radovanović, 2008; Wasserman & McIlroy, 1964).
There is no doubt about the importance of the determination of the AnT, however, there is still controversy surrounding the different forms to determinate de AnT.There are unnumbered methods to estimate ranging from invasive (blood lactate) or uncomfortable and expensive (spirographic, electromyograph-ic, magnetic resonance) and non-invasive methods (Bodner & Rhodes, 2000; Lopez-Chicharro, Calvo, Alvarez, Vaquero, Bandres, & Legido, 1995; de Assis, Piubelli, Mello, Pereira, Guerra, & Silva, 2015).In this subgroup are the determination of AnT through saliva, perceived exertion, deflection of the heart rate, talk test among others and which they maintain good reliability and at low cost.
The purpose of this review paper is to present the different non-spirographic and non-invasive methods that determine AnT.A research of different databases including EBSCO, Spordiscus specifically looking for "anaerobic threshold", "lactate threshold" and "ventilatory threshold" as was made.

METHOD
In this article bibliographical, historical and causal methods were used, with logical, deductive and inductive way of conclusion.Beside systematization of personal professional experience in practical determination of AnT, method of Theory analysis was used also.

RESULTS AND DISCUSSION
Most important characteristic of anaerobic threshold is that lactates in blood, after critical point shows sudden increase, which in a milder form leads to deterioration of concentration and co-ordination, and in extreme cases, to stopping of all activities (Damnjanović, 2016).Defining anaerobic threshold for specific athlete is a determining fact for the dosage of training, mainly in sports in which endurance is dominant component (rowing, canoeing, running, cycling, swimming etc.), (Grujić at all, 2017), but also in other sports in specific phase of preparation.On behalf of different parameters which were recorded on AnT level, specific "derived" AnT could be defined, such as speed of the boat during AnT, or stroke frequency during AnT, during specific time or length section in rowing, for each rower.(Ilić & Rajković, 2009).
There are many different methods of defining anaerobic threshold.In order for defining a useful method, it should be conductive, and should assess the width of the threshold with certain reliability.Determining the benefits of various methods including time requirements, invasiveness and money cost (Svedahl & MacIntosh, 2003).
Further in this article, disadvantages and benefits of some chosen non -invasive methods of defining AnT, with different protocols, are explained in accordance with their limits regarding original invasive methods (Table 1).

Anaerobic threshold using Heart Rate
In 1982 Conconi et al. developed one test that included 210 trained people.Research subjects needed to complete this test running in a sport track with an initial speed of 12-14 km/hr and increase their speed velocity at 0.5 km/hr every 200 m Authors discovered a linear incremental of HR at sub maximal velocities, however this not occur at maximal velocities (Conconi et al., 1982).In other words, at higher intensities the HR does not show a lineal incremental related with workload, although demonstrated a deflection in HR called heart rate deflection point (HR DP ).
The HR DP has been identified to the point where it slope values began to decrease and there is an evident loss of the linear slope values of HR (Bodner & Rhodes, 2000).Visual inspection seems to be a good method to determinate this break point by two or more experienced researchers, but mathematical or computer procedures possible present better accuracy (Sentija, Vucetic, & Markovic, 2007).Any of these methods can be used for sport performance predictions.
According to Vachon, Basse and Clarke (1999) conducted a research about the validity of HR DP as predictor of lactate threshold (LT).Eight male distance runner completed three different treadmills protocols and the Conconi test in track; they found the HR DP at maximal speed in all subjects in track.The same did not occur in the conventional laboratory test, in this scenario only half of sportsman present the HR DP .Author referred his findings as consequence of shortening of stages in track protocol (Vachon, et al., 1999).Bonder and Rodhes (2000) argued that HR DP concluding that these controversial results are due to the different protocols used to analyze them.Table 1 shows summaries about studies performed on athletes and their relationship with physiological variables, non-spirographic values can be a good predictor of anaerobic threshold but not in all cases.On the other hand, it has also been reported that HR DP can be a good predictor of AnT, since there are no differences in determining it by ventilatory methods or HR DP (Pinto et al., 2016) and also it is a good estimator of maximal lactate steady state (de Assis et al., 2015).Certainly, there is a moderate but significant correlation (r=0.51)found between HR DP and ventilatory threshold in young sport males according to (Buchheit, Solano, & Millet, 2007).However, this phenomenon can be influenced by several factors including left ventricular ejection fraction.Pokan et al.(1993), found an absence in HR DP, explained from the decreased efficiency of the left ventricle and it´s offset by increasing the HR in healthy adults (Pokan et al., 1993).
Extended works about HR DP shows high correlation (r=0.88) with ventilator threshold in sprinters, middle and long distance (Vucetić, Sentija, Sporis, Trajković, & Milanović, 2014).As well in two different protocols standard treadmill test (increment 1 km/h every 60 s) and fast treadmill test (increment 1 km/h every 30 s), authors evaluating 51 subjects and HR DP was evident in 47 (Sentija et al., 2007).Several authors conclude that HR DP may be an accurate predictor of AnT in most but not all subjects (Debray & Dey, 2007) It seems that HR DP it is an accurate way to determine AnT when considered: monitoring HR every 30 s, incremental protocols with initial speeds of 8 m/s increased from 1 km/h every 30 or 60 s and consider to use track or field protocols, even to control variables becomes even more complex in this environment is the closest to reality where the athlete develops.

Determination of AnT through saliva
The measurement of electrolytes through saliva has been considered an alternative way to determine AnT according to Lopez-Chicharro et al. (Lopez-Chicharro, Legido, Alvarez, Serratosa, Bandres, & Gamella, 1994).Authors used a sub maximal test in cycle ergometer and found high correlation (0.82) between saliva threshold and LT, saliva threshold and catecholamine threshold, and concluded that by measuring parameters in saliva is a good and non-invasive method to visualize AnT.Later, the same results was confirmed in children with no difference in blood lactate threshold and Na + and Cl + measured in saliva (saliva threshold) in a field test (Lopez-Chicharro, Calvo, Alvarez, Vaquero, Bandres, & Legido, 1995).The same occurred with the determination of lactate in saliva, high correlation (0.81) reported between this way to measure it and blood lactate assessment.Besides the authors point that 40 days after the saliva sample is taken it remains stable at 4ºC (Segura, Javierre, Ventura, Lizarraga, Campos, & Garrido, 1996).
In a progressive exercise protocol, subject performed until voluntary exhaustion and determination of blood and saliva lactate was assessment.The average values of saliva lactate were 6-20% compared to blood lactate and shows a parallel evolution of both.Saliva lactate can explain 93.4 % of the blood lactate (Oliveira, Oliveira, Manchado-Gobatto, & Costa, 2015) and with this support the idea of using saliva as lactate determination.In swimmer occur the same, high correlation (0.91) between blood lactate and saliva lactate determination was found, the protocol consisted of eight series of 100 m freestyle with increase of velocity.Both samples were taken simultaneously (Bocanegra, Diaz, Teixeira, Soares, & Espindola, 2012) and thus estimate the anaerobic threshold (Bortolini, De Agostini, Reis, Silva Lamounier, Blumberg, & Espindola, 2009) However, the determination of lactate in saliva could not be applicable in all populations.Is been reported that saliva lactate regarding blood lactate in athletes showed a stronger correlation (r=0.51)compared to sedentary people (r=0.38),mainly due to the physiological differences associated with adaptations in the central nervous system and circulatory system (Tékus et al., 2012) According to Claver, Mirón and Capitán-Vallvey (2009) the technique and standardization of the measuring lactate in saliva has been developed, results showed a good alternative method to assess at a low cost, quick, selective and sensitive and does not require an extensive specialization.

Using perceived exertion to determine Anaerobic Threshold
Among the different techniques developed exist the Borg´s scale, which has become one of most used techniques in perceived exertion, since mostly of parameters such lactate, HR, and electromyography, predicting through those values, how participants feel.However, it is recommended to be more accurate and ask directly to the participant how really he/she feels.However there is still controversy about the applicability of Borg´s scale, for example, a patient with a given HR workload may choose "hard" in just walking exercise, but his HR in running can reach higher levels (Borg, 1982;Grant et al., 1999).
Though, Borg´s Scale (a 15 points scale) has been used to determine the relationship between HR DP in 35 active males, but this was only possible with 24 participants authors reported at this point that views of Borgs 16 scale (e Silva, Dias, Franco, de Lima, & da Silva Novaes, 2008).In other hand no differences were noticed in women in physical activity level in Borg´s scale, both groups showed AnT closed to level 5 in Borg´s 10 points scale (Zamunér et al., 2011).In coronary artery disease patients show 5-6 values in ventilator anaerobic threshold determination, and results may be explained by their physical condition (Forti, Zamunér, Kunz, Salviati, Nery, & Silva, 2014) In heart failure patients the exercise guided by the Borg scale maintains the patient's HR between the anaerobic threshold in the exercise training zone important parameter in this populations (Carvalho, Bocchi, & Guimarães, 2009) and its use its recommended in physicians, physical therapist and medical staff for determining the intensity of resistance exercise in clinical practice (Mahler & Rostan, 1990; Morishita, Yamauchi, Fujisawa, & Domen, 2014)

Electromyography (EMG) Analysis to AnT determination
Electromyography analysis was used to determination of AnT in different populations and vastus lateralis regularly used for EMG, although sometimes cannot be explained or correlated due to an inter individual difference in the EMG.A progressive recruitment has been observed of fast twitch fibbers as work load increases (Helal, Guezennec, & Goubel, 1987).Occurring similar results in ten trained males in an incremental exercise protocol, it seems that inter subject variability in EMG cannot predict lactate threshold, instead EMG break point was shown after the appearance of lactate threshold (Taylor & Bronks, 1994) Meanwhile different results were presented by Tyka et al., (Tyka,

Table 1 .
Correlation between invasive and different non -invasive methods to estimate anaerobic threshold (Matsumoto, Ito, & Moritani, 1991)9) demonstrating a high correlation in EMG with lactate threshold (r= 0.91, 0.96 y 0.97) respectively for three different temperature exercise protocol (23, 31 y 37º Celsius) in 15 males.Moreover the EMG activity could be used as an indicator of the AnT (Viitalaso, Luhtanen, Rahkila, & Rusko, 1985).Matsumoto, Ito & Moritani (1991) used EMG fatigue threshold to determine AnT including 20 female college students, the sample consisted in high trained endurance athletes and sedentary individuals in cyclo-ergometer.Authors reported no difference in AnT and EMG at a given oxygen consumption, instead high correlation (r=0.823),concludingEMG it is an attractive alternative to measure AnT(Matsumoto, Ito, & Moritani, 1991)

SPIROGRAPHISCHE UND NICHT-INVASIVE METHODEN FÜR DIE EINSCHÄTZUNG DER ANAEROBEN SCHWELLE Zusammenfassung
Claver, Mirón,  & Capitán-Vallvey, 2009).Determination of AnT through non -invasive methods such as heart rate, saliva electrolytes or lactate, perceived exertion and electromyography among others, can predict sports performance with good reproducibility in almost all populations, redirect training and can help coaches and athletes to be more competitive.However, each of this parameter has some particularities and controversy due to different results reported by specialist.These differences may be explained by protocol testing used, sport level sample, starting intensity or number of levels among others.Despite this, they still have good reproducibility and applications on field based test protocols.Mentioned tests could be used in a large scale, and more often, with paying attention about level of correlation with original invasive tests, and percent of possible mistake in estimation process.Cheaper, and simpler tests (instead subjective estimation of training load) allows using more precise planning and changing volume, and intensity of training, for coaches, and athletes, that have needed level of education and less money.Athletes comfort, and possible high frequency of testing during non -invasive test, also must be emphasized as an advantage during training evaluation process.In der Welt von Sportuntersuchungen gibt es verschiedene Wege für die Einschätzung der Körperverfassung -die Palette reicht von teuren labor-invasiven Methoden bis zu billigen, nicht-invasiven Methoden im Gelände.Tests, die auf nicht-invasiven Methoden gründen, haben eine gute Zuverlässigkeit und einen niedrigen Preis für die Anwendung von physiologischen Parametern wie zum Beispiel: Puls, Elektrolyte oder Laktat aus Speichel, wahrgenommene Anstrengung und Elektromiographie.Diese Parameter können für die Einschätzung der anaeroben Schwelle (AnT) angewendet werden, die für Prognosen von Sportleistungen, Umgestaltung von Trainings verwendet wird und Trainern und Sportlern helfen kann, wettbewerbsfähiger zu werden.Jeder dieser Parameter hat jedoch seine Eigentümlichkeiten und Kontroversen wegen unterschiedlicher Ergebnisse, die von Experten präsentiert werden.Diese Unterschiede können unter anderem durch Prüfungen der angewendeten Protokolle, durch die Musterebene der Sportler, die anfängliche Intensität oder die Anzahl der Qualitätsebenen der Sportler erklärt werden.Trotz allem haben sie auch weiterhin eine gute Wiederholbarkeit und Anwendung auf Prüfungen der Protokolle, die auf den Geländebedingungen gründen.Die angeführten Tests können in bedeutendem Maße angewendet werden, wobei die Korrelationsstufe mit originellen invasiven Tests und der Prozentsatz möglicher Fehler im Einschätzungsprozess beachtet werden müssen.Billigere und einfachere Tests (anstatt subjektiver Einschätzungen der Trainingsbelastung) ermöglichen eine präzisere Planung, änderen den Umfang und die Intensität des Trainings für den Trainer und den Sportler und fordern somit eine niederigere Bildungsebene und weniger finanzielle Mittel.Der Komfort der Sportler und mögliche häufigere Untersuchungen im Laufe von nicht-invasiven Tests können als Vorteil während des Evaluierungsprozesses von Trainings hervorgehoben werden.