KINESIOLOGIASLOVENICA 1995; 2 (1): 17-21 17 DO THE CLASSICAL ESTIMATORS: LACTATE THRESH0LD AND ONSET 0F BLOOD LACTATE ACCUMULATI0N ASSESS ENDURANCE IN A SIMILAR WAY? Anton Ušai* ALI KWIČNA KAZALCA: LAOATNI PRAG IN ZAČDEK AKUMULACIJE LAKTATA 0CENJUJOA VZDRŽLJIVOST NA PODOBEN NAČIN? ABSTRACT Lactate curves varied in their position in relation to the x and y axes and inclination of their steeper part when they are represented in diagrams of lactate concentration related to running velocity. lf they va- ried more in their position and less in their inclina- tion, then there were parallel variations of both cha- racteristic points: Lactate Threshold (LT) and Onset of Blood LactateAccumulation (OBLA). In thatcase, correlation between both velocities should be sig- nificant and stable. lf curves varied significantly also in their inclination, then there should be non-signi- ficantand varied correlation between LT and OBLA. To testthis hypothesis, seven runners participated in a standard testing protocol on the treadmill to de- termine LT and OBLA. They repeated the same test four times in the training period from June to September. The calculated correlatio n coefficients showed a very unstable relationship between LT and OBLA. In June it was 0.12, in July 0.83 (P< 0.05) in August0.46 and in September0.82 (P< 0.05). There was no significant change of running velocity deter- mined by LT and OBLA. The reason for such great variabi lity was inter-subject changes of observed ve- locities, caused mostly by changes in the inclination of the steeper parts of the lactate curves, which were more pronounced than were changes of their posi- tion. The independence of changes of both veloci- ties was only noticed for some subjects. Some others showed very parallel changes of both velocities, throughout the four months period of training. It seems that both characteristic points don't estimate endurance in the same way, or there are different types of running endurance. Some types may be more related to LT, others more to OBLA. Key words: lactate curve, lactate threshold, onset of blood /actate accumulation, interrelationship, trai- ning effect • Faculty of sport, University of Ljubljana, Ljubljana, Slovenia IZVLEČEK Laktatne krivulje se spreminjajo v d iagramih odvis- nosti koncentracije laktata ([LA)) od hitrosti teka (v). Spremembe se kažejo v njihovem položaju glede na obe osi, v spremembah oblike laktatne kri~ulje, pa tud i v strmosti njihovega strmejšega dela. Ce spre- minjajo bolj svoj položaj, kot omenjeno strmost, potem so spremembe hitrosti, ki jih določata oba kri- terija: Laktatni prag (LT) in Prag izraženega povečan­ ja koncentracije laktata (OBLA) skladne, kar je mogoče zaznati z visokimi v~ednostmi medsebojnih korelacijskih koeficientov. Ce pa krivu lje bolj spre- minjajo svojo strmost, potem se lahko zgodi, da se vrednosti korelacijskih koeficientov zelo spreminja- jo. Za testiranje resničnosti te hipoteze, je sedem tekačev sodelovalo v štirih standardnih testih, v ob- dobju štirih mesecev priprav na tekmovalno obdob- je. Hitrosti, ki jih določata oba kriteri ja: LT in OBLA, se dejansko lahko skladno ali pa neodvisno spre- minjajo. Korelacije med obema hitrostima so na primer v juniju 0.12, v jul iju 0.83 (P<0.05), v avgu- stu 0.46 in v septembru 0.82 (P<0.05). Pri tem se obe povprečni hitrosti nista statistično značilno spre- menili. Razlog za takšno izraženo variabi lnost ko- relacij med obema hitrostima je mogoče pripisati neskladnim spremembam strmejših delov krivulj. Zgleda, da obe hitrosti ne ocenjujeta vzdržljivosti na enak način ali, da obstajajo različne vrste vzdr- žljivosti (najmanj dve), na katere vadba specifično učinkuje. Ključne besede: laktatna krivulja, /aktatni prag, prag izraženega povečanja koncentracije /aktata, medse- bojna zveza, učinek vadbe 18 Anton Ušaj DO THE CLASSICAL ESTIMA TORS: LACTATE THRESHOLD ANO ONSET OF BLOOD LACTATE CCUMULATION ASSESS ... ? INTRODUCTION It is well known that the Lactate Threshold (LT) and other criteria which use fixed lactate concentrations, such as Onset of Blood Lactate Accumulation (OBLA), are very related to the endurance performance in run- ning (4,8, 1 O, 11, 12). The two criteria base on different characteristics of the lactate curve in diagrams of the lactate concentration ([LA]) dependence on running velocity. LT is determined by the initial increase of [LA], which is related to a marked increase of lactate turnover in muscles and the whole organism, which results in greater [LA] appearance over its disappear- ance, which causes lactate accumulation in blood (1,2,5). The criterion OBLA uses a different base, a predetermined [LA]= 4 mmol/1 (6,7). This criterion may indicate (oris related to) the highest velocity of running where [LA] is stili in a steady state, even if the exercise continues for a longer tirne (approximately 1-2 hours)(1,2). Both criteria determine two clearly diffe- rent points on the lactate curve in the diagrams of de- pendence of [LA] on running velocity (6, 12). The dif- ference was shown by [LA] which was about 1-2 mmol/1 at the point of LT and exactly 4 mmol/1 at the level of OBLA. The difference was shown also by running velocity which was approxi mately 10% higher at OBLA than at LT (12). The position of the LT and OBLA points in diagrams could change if the position or/and shape of the lactate curve changed. The position of lactate curves in diagrams of [LA] dependence on running velocity is related to endurance in running. The posi- tion of the lactate curve is located more in the higher running velocity range and the lower [LA] with more endurance runners. For subjects with low endurance, the position of the lactate curve is located more to the lower running velocities area and to the higher [LA] (1,5, 1 O, 12). Lactate curves can also be different in the gradient of their steeper part, maybe independently of other characteristics. This variabi I ity i nfluences on ly the value of runningvelocity determined by OBLA and not the velocity determined by LT. Both criteria do not nec- essarily determine endurance in a similar way if we base this idea on the really strong correlation of both velocities with endurance in running. It is possible to test this hypotheses in two ways. Firstly, we made a comparison between running velocity determined by both criteria. Secondly, we related both velocities with each other for each subject, that participated in the study, duringthe training period of four months, to find if stability or instability occurs for the same person. SU BJ ECTS AND METHODS Subjects A group of 7 cross-country skiers voluntarily partici- pated in the study after al i had given written in- formed consent. Testing protocol The used protocol is a part of their usual testing procedure. Each runner participated in a standard- ised exercise protocol on the treadmill. The running velocity was increased each tirne for 0.2 m/s in five or more runs of 5 min duration. The initial running velocity was selected so that the heart rate did not surpass 120 b/min. The final running speed is de- fined as that which produced either a heart rate greater than180-190 b/min, or exhaustion. The runs were interrupted by breaks of up to 30 s for blood sampling. The numberof runs depended on the ini- tial running speed and on the runner's endurance. The same testing protocol was repeated four times (once per month) during the preparatory period. Blood collection and biochemical analysis Capil lary blood sam ples (20 µI) were collected after each run from an hyperemied ear lobe. The con- centration of blood lactate ([LA]) was determined us- ing a Kontron 640 Lactate Analyser (Kontron, Austria). Data processing and analysis The criterion LT was determined by using the two component analysis of [LA] kinetics. The method used was based on the principles described by Beaver et al (2, 12). LT was defined as the intersec- tion poi nt of the two best fitted exponential interpo- lating curves, calculated from data in the diagram of [LA] dependence on running speed (Fig. 1). Data was firstly transformed by using a semilog (log[LA]/velocity) transformation for accurate deter- mination of LT and then was represented in the ori- ginal diagram as two exponential curves. The inter- section point is described by the corresponding run- ning speed (VLT), the value of [LA] (LALT), and by the corresponding HR (HRLT). Analysis of the [LA] kine- tics also included t he use of the OBLA criterion, which used a constant value of [LA]= 4 mmol/1 6. 0 ,-----r-- ~--~-----,- ----, 5 .5 5 .0 ~ .s 4 .5 ...., > 4.0 J une Ju ly Aug . Sept. Fig. 1 Running ve/ocity Vit showed nonsignificant changes during the experimenta/ period. At first there was a tendency for the values to increase Uune through August) and in tlie last month (September) to decrease. Anton Ušaj . -1 9 DO THE CLASSICAL ESTIMATORS: LACTATETHRESHOLDAND ONSETOF BLOOD LACTATE CCUMULATION ASSESS .. ? 1 ~ E ~ ..o .g 6.0 5.5 5.0 4 .5 4 .0 3 .5 June Ju ly Aug. Sept . Fig. 2 Running speed V,,.~ showed nonsignificant changes during the experimenta/ period. There was a tendency for tlie va/ues to in- crease. (6,7, 1 O). The corresponding velocity was then de- noted as Vos"' and HRootA. Statistics Arithmetic means, standard deviations, standard er- rors of estimation and correlation coefficients were calculated usinga CSS: STATISTICA statistical pack- age (Statsoft, USA). The differences in running velocity determined by LT and thatdetermined byOBLA throughoutthe ex- perimental period were analysed using a Kruskal - Wallis ANOVA test. The significance level of P =O.OS was selected for testing the significance of diffe- rences and also for proving the significance of the correlation coefficients. 6 .0 r=0.12 r=0 .83 N=7 N=7 5.5 ~ ~ 5.0 .C ·o _Q Q) > 4.5 00 C C C ::i er: • 4.0 o LT OBLA LT OBLA 3.5 JUNE JULY RESULTS The runn ing velocity Vit is 4.2±0.2 m/s (mean, SO) in June (Fig 1 ). Velocity vootA was 4. 9±0.2 m/s (Fig. 2). The correlation between both velocities was r=0.12 (Fig. 3a). There was an insignificant increase of Vit to the - level of 4.3±0.1 m/s (Fig. 1) and of vootA to the level of 5.0±0.2 m/s (Fig. 2), after one month of en- durance traini ng. The correlation between both ve- locities in this case was r=0.83 (Fig. 3). There was a tendency for a continuous increase of both running velocities in relation to their values in June and July (Fig 1 and 2). But this increase was not significant. Running speedVltwas4.3±0.1 m/sand vastA was 5.0±0.2 rn/s. The correlation between thern was r= 0.46 (Fig. 3). There were only 5 subjects in tests in September. Running speed Vit was 4.2 ±0.1 m/s and vootA was 5.0±0.2 m/s. The correlation between them was r=0.82 (fig. 3). According to very dramatical changes in the cor- relation coefficients between both running veloci- ties frorn rnonth to month and non-significant changes of the observed running velocities it can be concluded that both velocities changed their values relatively independently, which can be seen when both running velocities were represented for each subject, during the experiment (Fig. 4,5 ,6,7). Some subjects showed sirnilar and parallel changes of both r =0.46 r = 0.82 N= 7 N=5 • o III 'i7 o~• LT OBLA LT OBLA AUGUST SEPTEMBER Fig. 3 Correlation relationship between Vit and V"""' in each o( the observed months of the experimental period. Values changed dramati- cally from month to month because of the changes in the relationship between both velodties in the group as a whole. 20 Anton Ušaj DO THE CLASSICAL ESTIMA TORS: LACT ATE THRESHOLD ANO ONSET OF BLOOD LACT A TE CCUMULA TION ASSESS ... ? 6.0 f F 046 5.0 A i -•- • B 5.5 ----- .. ----- . ril [/J "-... "-... • .. E s r=-0.17 .._,. j 5 .0 ... - .. ::,.., 4.5 >, ...·· ....., ....., .... o. (.) (.) •, o o '•. 4 .5 -(l) O-... __ o <1) ·o--- . ·O > / .. ·-o -· .. > o o 4.0 4.0 Jun e Ju ly Aug. Sept. J une July Aug. Sep t. 5 .0 6 ----- 1 .. C ril '-, .. - ······· ........ r=0.98 D "-... ---. -----s [/J ' r=-0.87 "-... 4 .5 E 5 --- . --- ---------·····-·••'-------- ---· >, -....., () >, o .o .... -0----0 ....., .o . ~ 1 (.) ·~o (l) o o--------• -> 4. 0 o -1 4 1 Q) LEGEND > 1 0 Vit ! • Vobla 3.5 3 June ciUly Aug. Sept. June J uly Aug. Sept. Fig. 4 Ch~~ges ofV/t and Vow. during the experimental period for four particu/ar subjects showed great variability in response to very simi/ar tra1ning. The changes of Vit and V°""' coufd be very simi/ar, or very different for individual. velocities from June throughout September and a high correlation between the individual points, de- termined by the two criterions (Fig. 5, 7). On the other hand, some of the subjects showed indepen- dentvariations in the selected velocities forthe same period and a very low correlation (Fig. 4,6). DISCUSSION Endurance in running is defined as the highest pos- sible running speed on distances between 5 km and 42.195 km (marathon). As it is a complex multifac- torial ability, it is unrealistic to expect that the same type of endurance is the most important factor in running on 5 km and 42.195 km. Also, the best world-ranked runners are not present at the top in both running disciplines. So it may be necessary to understand and define running endurance as per- formance, which can be distance-and intensity-spe- cific. According to this premise, it is possible to se- parate endurance in general into two groups: short (SE) and long endurance (LE}. Physiological charac- teristics representative of SE are: a high level of maxi- mal oxygen consumption (Vo2 max), lower lactate production and a greater lactate degradation (greater turnover), more developed buffer systems and maybe also better adaptation to increased metabolic acidosis (9, 12). On the other hand, the most evident characteristics that represent LE are: a lowerglycogen uptake; a greater uptakeof fat as free fatty acids (FFA) and glycerol than glucose; and a lower lactate production (3,9). lntense correlation between lactate curve charac- teristics such as LT and OBLA, and running en- durance is well known and accepted (4,8, 11 , 12). LT and OBLA defined two significant different running velocities (the difference varied between 8 - 15 %) (12). Running speed for the S km distance and the marathon are also clearly different. Because of these dissimilarities it is possible to make a hypothesis that sometimes both criteria individually relate more to specific endurance. Because trained runners have developed a specific endu rance, the correlation be- tween both SE and LE on one; and LT and OBLA on the other side, can't always be significant. That endurance training increases endu rance is very clear for non-trained subjects. Running velocity de- termined by LT and OBLA increased in a more or less similar way. In a homogenous group of endurance Anton Ušaj DO THE CLASSICAL ESTIMA TORS: LACTATE THRESHOLD ANO ONSET OF BLOOD LACTATE CCUMULA TION ASSESS ... ? 21 trained runners, the effectof training may not be uni- directional. Differences in absolute values may be smal l, but relative to the values inside the group, there can be relatively large variability, which can be seen from the rather marked variabil ity of correla- tion coefficients from month to month in our study. Effect of the training is also individual, which can be seen very clearly from the different responses for both running velocities, when they were related to each other for the same subject throughout the ex- perimental period. AII these specific responses of a trained group of runners show the necessity for rela- tively independent use of LT and OBLA and special care must be taken when lactate curves are inter- preted. 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