The highest intensity that can be maintained over time without continual blood lactate accumulation has been termed maximal lactate steady state (MLSSw) (2). The determination of MLSSw has been conducted using blood lactate measurements during a series of 30-minute, constant-workload tests. The criterion that has traditionally been used to determine MLSSw is an increase of blood lactate concentration ([La]) by no more than 1.0 mmol·L−1 during the final 20 minutes of the test (6,11,12). Thus, MLSSw seems to indicate an exercise intensity above which the rate of glycolysis exceeds the rate of mitochondrial pyruvate use, causing net lactate formation (6,11,17). The MLSSw can discriminate qualitatively between sustainable exercise intensities, in which continuous work is limited by stored energy and exercise intensities that have to be terminated because of a disturbance of cellular homeostasis (3).
Continuous aerobic training sessions at or near MLSSw can improve aerobic performance in endurance athletes (19). However, interval training consisting of repeated long bouts of rather high-intensity exercise (equal or superior to MLSSw) interspersed with recovery periods (light exercise or rest) (14) may be essential for further improvements in aerobic performance in trained subjects (16). It has been demonstrated that test interruptions for blood sampling modify the level of physiological exertion during the tests and may modulate the MLSSw (5). Indeed, MLSSw was lower during continuous protocol (MLSSwc) (277.8 W) when compared to intermittent protocols (MLSS during intermittent protocols [MLSSwi]) using 5-minute bouts interspersed with 30 seconds (300.4 W) or 90 seconds of rest (310 W) (5). Thus, using training loads higher than MLSSw during interval training may also determine stability of [La]. This can be explained, at least in part, by the partial resynthesis of creatine phosphate stores and blood lactate removal during recovery periods (10,15,22). Thus, the protocol used to determine MLSSwc may have limited application for submaximal aerobic interval training prescription for endurance athletes. Additionally, the [La] is reduced if submaximal exercise is performed during the recovery period (active recovery), when compared with passive recovery (1,7,9,18), by the increased blood lactate removal rates (9,20). Although the intermittent protocols may present advantages in relation to the individualization of the interval training intensity prescription, they tend to be long because of the recovery periods, if we consider the total duration (30 minutes) recommended (4).
The recovery periods during intermittent exercises reduce the glycolytic flux of the previously active muscles (4), which could generate a delay in the [La] kinetics before the steady-state condition is attained. The time course of [La] at the beginning of constant-workload exercise is determined by [La], steady state [La], and the time constant (τ) of the [La] response (12). It has been reported that at least 92% (τ ∼ 2.5 minutes) of the final steady state [La] during continuous constant-workload exercise was attained only after 10 minutes (4). In this condition, the first blood collection for [La] analysis is performed at 10 minutes after the beginning of the exercise (4). Because blood lactate is adjusted to attain the workload level during the first 10 minutes of the exercise, the inclusion of the recovery times for blood samples until this moment may alter the typical time course of the changes in [La] kinetics and, consequently, MLSSwi. Therefore, it is possible to hypothesize that (a) the period of time considered (including or not including the duration of the recovery periods) for the interpretation of [La] kinetics during an intermittent protocol using passive recovery may modify the MLSS and MLSSwi, and (b) the active recovery may modify MLSS and MLSSwi when compared to the passive recovery condition.
This study was undertaken to analyze the effect of the measurement time for blood lactate determination during prolonged intermittent exercises performed with passive and active recoveries on the MLSS and MLSSwi.
Experimental Approach to the Problem
The hypothesis that the period of protocol observed for the interpretation of [La] kinetics during prolonged intermittent exercise may modify the MLSS and MLSSwi was tested. Basically, we tested whether considering or not considering the recovery periods for the blood collection may modify MLSS and MLSSwi. To do this, the time course of the changes in [La] during constant-workload tests were compared using 2 different criteria in the same test: criterion 1 (T1)—blood lactate variation between 10th and 30th minutes of the entire protocol (i.e., considering effort + recovery periods) and criterion 2 (T2)—blood lactate variation between 14th and 44th minutes of the protocol (i.e., considering only the exercise duration around MLSSwi). This allowed analyzing how dependent variables (MLSS and MLSSwi) changed when considering (T1) or not considering (T2) the recovery periods (i.e., time is the independent variable) during the prolonged intermittent exercise. To verify the effect of the recovery mode on MLSS and MLSSwi, the subjects were divided into 2 groups that performed the protocol with passive or active recovery.
Nineteen trained male cyclists, with at least 5 years of experience in the modality and who were competing in regional- to national-level meets volunteered to participate in this study, and appropriate written informed consent was gained. They were specialized in road cycling events and were training 6–7 times a week, with a mean weekly volume of 403 ± 50 km. They were in the preparation phase of the training program. Subjects were matched according to V̇O2max and then randomly assigned to 2 subgroups. Passive: 9 participants whose MLSSwi was determined using passive recovery (Age = 25.8 ± 3.4 years, Body mass = 74.4 ± 8.4 kg, Stature = 174.3 ± 6.5 cm)/Active: 10 participants whose MLSSwi was determined using active recovery (Age = 25 ± 4 years, Body mass = 71.8 ± 9.07 kg, Stature = 175.8 ± 7.5 cm). The project was approved by the University Ethic's Committee (Protocol 144/2007).
The subjects were required to visit the laboratory on to 3–5 different occasions within a period of 3 weeks. Each subject performed the following tests: (a) An incremental test to determine anaerobic threshold (AT), V̇O2max, and the workload associated with V̇O2max (Wmax) and (b) 2–3 intermittent submaximal constant-workload tests with either passive or active recovery. The interval between 2 submaximal constant-workload tests was at least 48 hours. Pedal frequency was maintained at a constant 70 rpm for all cycle tests. Subjects were instructed to be fully rested and hydrated, at least 3-hour postprandial when reporting to the laboratory and to refrain from using caffeine-containing food or beverages, drugs, alcohol, cigarette smoking, or any form of nicotine intake 24 hours before testing. Each subject was tested in a climate-controlled (21–22°C) laboratory, at the same time of the day (±2 hours) to minimize the effects of diurnal biological variation.
Subjects performed all tests on an electromagnetically braked cycle ergometer (Excalibur Sport, Lode BV, Croningen, The Netherlands). Capillary blood samples were collected from the ear lobe into microcentrifuge tubes containing 50 μL NaF (1%) for the determination of [La] (YSL 2300 STAT, Yellow Springs, OH, USA). Pulmonary gas exchange was measured continuously during the incremental protocol using a breath-by-breath analyzer (Quark PFTergo, Rome, Italy).
The initial workload was set at 100 W with increments of 25 W every 3 minutes until voluntary exhaustion. Strong encouragement was provided throughout the tests. V̇O2max was defined as the highest 15-second average V̇O2 value reached during the incremental test. Capillary blood samples were collected within the final 20 seconds of each stage for the determination of [La]. Least square regression analysis was carried out on the second per second oxygen uptake data to determine the slope of V̇o2 vs. work rate (ΔV̇O2/ΔW). Plots of [La] against V̇O2 were provided to 2 independent reviewers, who determined lactate threshold (LT) as the first sudden and sustained increase in blood lactate above resting concentrations. The AT was determined by linear interpolation and defined as the workload corresponding to a blood lactate concentration of 3.5 mmol·L−1 (8).
Determination of Maximal Lactate Steady State
In the passive condition, cyclists performed 7 repetitions of 4-minute exercise intercepted with 2 minutes of passive recovery plus 2 minutes of exercise. This was for the duration of the cycling to be 30 minutes as recommended by Beneke (4) with a work:rest ratio of 2:1 (14). The total duration of the constant submaximal workload test was 44 minutes, and several were performed per subjects to determine their individual MLSSwi. The first test was performed at 110% AT. The workload was then adjusted at ±5% according to the blood lactate response during the previous test. The MLSSwi was defined as the highest workload at which [La] did not increase by >1 mmol·L−1 between T1, at minute 10 vs. 30 (end of the second vs. fifth repetition) and T2, minute 14 vs. 44 of the test. It is important to note that, in addition to considering only the exercise duration around MLSSwi, the T2 used the last 20 minutes of exercise around MLSSwi, in accordance with Beneke and Von Duvillard (6). The [La] corresponding to MLSSw (MLSS) was calculated as the average [La] measured at the 10th and 30th minutes for T1 and at the 14th and 44th minutes for T2.
In the active condition, cyclists performed 7 repetitions of 4-minute exercise intercepted with 2 minutes of active recovery at 50% Wmax plus 2 minutes of exercise. The total duration of the repetitions (30 minutes) and protocol (44 minutes), the initial (110% AT) and the variation of workload (±5%), and the moment of blood collection for [La] analysis (i.e., T1 and T2) were the same used during intermittent protocol with passive recovery (Figure 1).
Data are reported as mean ± SD. The normality of data was checked by the Shapiro–Wilk test. The data were analyzed using 2-way analysis of variance (criterion vs. recovery mode), with Scheffé's post hoc test where appropriate. Differences in characteristics of the subjects were evaluated from unpaired t-tests. For all statistics, the significance level was set at p ≤ 0.05.
The variables obtained during the incremental protocol are shown in Table 1. There was no significant difference in V̇O2max, Wmax, V̇O2, and LT expressed in absolute and relative values and ΔV̇O2/ΔW efficiency between groups (p > 0.05).
The individual responses of [La] at minute 10 (T1) and 14 (T2) of the intermittent protocols performed using passive and active conditions are shown in Figure 2. [La] at minute 10 (5.80 ± 1.23 mmol·L−1) was not significantly different from that obtained at minute 14 (5.64 ± 1.83 mmol·L−1) (p = 0.708) in the passive condition. However, these values were significantly different in the active condition (minute 10—5.44 ± 1.94 mmol·L−1; minute 14—4.63 ± 1.92 mmol·L−1) (p = 0.011).
There was no significant effect of the recovery mode for MLSSwi (F = 4.31, p = 0.054), %Wmax (F = 4.31, p = 0.054), MLSS (F = 0.409, p = 0.531), and Δ[La] (F = 0.01, p = 0.93). There was no significant effect of criterion for MLSSwi (F = 0.27, p = 0.60), %Wmax (F = 1.16, p = 0.29), and Δ[La] (F = 3.78, p = 0.06). However, there was a significant effect of criterion for MLSS (F = 13.14, p = 0.002). The MLSS was lower in T2 (4.91 ± 1.91 mmol·L−1) when compared with in T1 (5.62 ± 1.83 mmol·L−1) using active recovery (p = 0.032) (Table 2).
Previous study has proposed that constant-load tests lasting at least 30 minutes, and a [La] increase of no more than 1.0 mmol·L−1 after the 10th testing minute is the valid protocol to determine MLSS and MLSSwc (4). The main finding of this investigation was that the MLSSwi (passive and active conditions) and MLSS (passive condition) were not modified whether recovery periods were considered (T1) or not considered (T2) for the interpretation of [La] kinetics. In contrast, MLSS was reduced when considering only the exercise duration around MLSSwi (T2) in the active condition. These latter results suggest that active recovery periods were able to modify metabolic condition but were not enough to change the power output (MLSSwi). Therefore, our hypothesis was not entirely confirmed by the results. This study shows that shorter protocols may be conducted to determine MLSSwi, avoiding long (>50 minutes) endurance tests, which may optimize the endurance athletes' evaluation.
Irrespectively of the criterion (T1 and T2), the MLSS obtained in this study (passive ∼5.7 mmol·L−1; active ∼5.2 mmol·L−1) were similar to that found during continuous (5.1 mmol·L−1) (4) and intermittent conditions using bouts of 5 minutes interspersed with 30 seconds (5.7 mmol·L−1) or 90 seconds (5.9 mmol·L−1) (5). In fact, Beneke et al. (5) did not verify the significant effect of test interruptions on the MLSS. Thus, the criterion used to determine MLSS (test duration, period of constant-load exercise observed for the interpretation of the [La] kinetics, and the maximally accepted increase in [La]) during continuous exercise (increase of not >1 mmol·L−1) seems to be also valid for the [La] analysis for intermittent exercise.
This study is the first to investigate the effect of period of constant-load exercise observed for the interpretation of the [La] kinetics on the MLSS and MLSSwi. In the passive condition, [La] values were similar when considering (T1—minutes 10 and 30) or not considering (T2—minutes 14 and 44) the recovery periods. During the recovery periods of intermittent exercises, the glycolytic flux of the previously active muscles is reduced. Depending on the exercise intensity and the conditions of the recovery period (duration and mode), this could generate a delay on the [La] kinetics before the steady-state condition is attained. However, when exercises are performed at and above MLSS, there is substrate saturation (3). Thus, the lactate appearance in blood compartment may not be modified, even with reduced glycolytic flux, during the recovery periods. In the active condition, [La] values were lower when considering T2 for the determination of MLSS. When considering T1 and T2, the exercise around MLSS (8 and 10 minutes, respectively) and recovery (2 and 4 minutes, respectively) durations before the first blood collection were not similar. Because between 8 and 10 minutes of constant-workload exercise, the [La] was almost at a steady-state level (4), the most probable factor that can probably explain the lower [La] in T2 was the longer active recovery period. However, the changes in the [La] at the beginning of the exercise are not enough to modify the mean [La] response. Other studies have also verified that active recovery improved blood lactate clearance but not the performance in supramaximal 40- to 45-second exercises interspersed with 90 seconds of recovery (13,21).
An interesting finding of this study was that Δ[La] did not change significantly, irrespectively of the criterion (T1 vs. T2) and recovery mode (passive vs. active). Considering T1, there were 12 minutes of exercise around MLSS between the first and second moments of [La] analysis. However, this period was longer (20 minutes) when using T2 to analyze the [La] response. Beneke (4) using the continuous protocol to determine MLSS has suggested that there must be at least 20 minutes of constant-workload exercise, to apply delta variation of 1 mmol·L−1 between the 2 points of [La] analysis (i.e., 0.05 mmol·L−1·min−1). In this study, the author found similar MLSSw values but lower MLSS values when considering only 10 minutes of constant-workload exercise (10th–20th minutes; 0.05 mmol·L−1·min−1) when compared to 20 minutes (10th–30th minutes). In our study, although lower MLSS values were found in the active condition, this was not enough to change the power output (MLSSwi), suggesting that MLSSwi may be determined using shorter protocols. One of the limitations of this study was the division of athletes into 2 groups for determining MLSS with passive and active recoveries separately, which could be influenced by the individual variability on blood lactate response during submaximal exercise. However, the subjects were divided into 2 groups with similar physiological indexes (incremental protocol). Therefore, the possibility of individual variability influences on the MLSSwi comparisons was reduced. In this study, although an individual variability in [La] corresponding to MLSS exists, the modifications induced by this variable in other MLSS parameters may be presumably minor in comparison with those induced by MLSS criterion and recovery type.
We conclude that the inclusion of recovery period for the [La] kinetics analysis does not influence the determination of MLSSwi during prolonged intermittent protocols lasting ∼45 minutes performed with passive and active recoveries. However, more studies are required using intermittent protocols with different effort and recovery durations to understand the influence of recovery period on the MLSSwi and MLSS more fully.
In practical terms, intermittent protocols are essential for interval training prescription, which may be important for further improvements in aerobic performance of trained subjects (16). However, they are longer than continuous protocols because of the recovery periods. In this way, an important implication of our data is that shorter protocols considering the exercise and recovery periods for blood lactate measurements (at minutes 10 and 30) are suitable for detecting the MLSSwi, which can reduce the time needed for aerobic evaluation. Therefore, it is not necessary to conduct long intermittent protocols (>50 minutes) for MLSSwi determination. Moreover, because test interruptions may modify the MLSSw (5), we recommend the use of intermittent protocols for aerobic interval training prescription performed by endurance cyclists.
We thank the subjects for participation in this study and Fundac¸ão de Amparo à Pesquisa do Estado de São Paulo (FAPESP) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for financial support.
1. Belcastro, AN and Bonen, A. Lactic acid removal rates during controlled and uncontrolled recovery exercise. J Appl Physiol
39: 932–936, 1975.
2. Beneke, R. Anaerobic threshold, individual anaerobic threshold, and maximal lactate steady state in rowing. Med Sci Sports Exerc
27: 863–867, 1995.
3. Beneke, R. Maximal lactate steady state concentration (MLSS): Experimental and modelling approaches. Eur J Appl Physiol
88: 361–369, 2003.
4. Beneke, R. Methodological aspects of maximal lactate steady state implications for performance testing. Eur J Appl Physiol
89: 95–99, 2003.
5. Beneke, R, Hutler, M, von Duvillard, SP, Sellens, M, and Leitthauser, RM. Effect of test interruptions on blood lactate during constant workload testing. Med Sci Sports Exerc
35: 1626–1630, 2003.
6. Beneke, R and von Duvillard, SP. Determination of maximal lactate steady-state response in selected sports events. Med Sci Sports Exerc
28: 241–246, 1996.
7. Bonen, A and Belcastro, AN. Comparison of self-selected recovery methods on lactic acid removal rates. Med Sci Sports
8: 176–178, 1976.
8. Denadai, BS, Figueira, T, Favaro, O, and Gonçalves, M. Effect of the aerobic capacity
on the validity of the anaerobic threshold for determination of the maximal lactate steady state in cycling
. Braz J Med Biol Res
37: 1551-1556, 2004.
9. Dodd, S, Powers, SK, Callender, T, and Brooks, E. Blood lactate disappearance at various intensities of recovery exercise. J Appl Physiol
57: 1462–1465, 1984.
10. Dupont, G, Moalla, W, Guinhouya, C, Ahmaidi, S, and Berthoin, S. Passive versus active recovery during high-intensity intermittent exercises. Med Sci Sports Exerc
36: 302–308, 2004.
11. Heck, H, Mader, A, Hess, G, Mucke, S, Muller, R, and Hollmann, W. Justification of the 4-mmol/l lactate threshold. Int J Sports Med
6: 117–130, 1985.
12. Heck, H, von Rosen, I, and Rosskopf, P. Dynamik des Blutlaktats bei konstanter Fahrrad- und Drehkurbelarbeit. In: Regulations- und Repairmechanismen
. H. Liesen, M. Weiß, and M. Baum, eds. Köln, Germany: Dt Ärzte-Verlag, 1994. pp. 187–190.
13. Lau, S, Berg, K, Latin, RW, and Noble J. Comparison of active and passive recovery of blood lactate and subsequent performance of repeated work bouts in ice hockey players. J Strength Cond Res
15: 367–371, 2001.
14. Laursen, PB and Jenkins, DG. The scientific basis for high-intensity interval training
: Optimising training programmes and maximising performance in highly trained endurance athletes. Sports Med
32: 53–73, 2002.
15. Linossier, MT, Dennis, C, Dormois, D, Geyssant, A, and Lacour, JR. Ergometric and metabolic adaptation to a 5-s sprint training programme. Eur J Appl Physiol
67: 408–414, 1993.
16. Londeree, BR. Effect of training on lactate/ventilatory thresholds: A meta analysis. Med Sci Sports Exerc
29: 837–843, 1997.
17. Mader, A and Heck, H. A theory of the metabolic origin of ‘‘anaerobic threshold.’’ Int J Sports Med
7: 45–65, 1986.
18. Monedero, J and Donne, B. Effect of recovery interventions on lactate removal and subsequent performance. Int J Sports Med
21: 593–597, 2000.
19. Philp, A, Macdonald, AL, Carter, H, Watt, PW, and Pringle, JS. Maximal lactate steady state as a training stimulus. Int J Sports Med
6: 475–479, 2008.
20. Spierer, DK, Goldsmith, R, Baran, DA, Hryniewicz, K, and Katz, SD. Effects of active vs. passive recovery on work performed during serial supramaximal exercise tests. Int J Sports Med
25: 109–114, 2004.
21. Watson, RC and Hanley, RD. Application of active recovery techniques for a simulated ice hockey task. Can J Appl Sport Sci
11: 82–87, 1986.
22. Yoshida, T, Watari, H, and Tagawa, K. Effects of active and passive recoveries on splitting of the inorganic phosphate peak determined by 31P-nuclear magnetic resonance spectroscopy. NMR Biomed
9: 13–19, 1996.