The origin of the maximal lactate steady state (MLSS)

The maximal lactate steady state, abbreviated as MLSS, is the maximal exercise intensity where the concentration of earlobe capillary or arterial blood lactate remains constant over time. In the late 1970s and early 1980s, we (i.e. Hermann Heck and co-workers) developed a direct test to determine the MLSS to investigate whether it occurred at a lactate concentration of 4 mmol.L- 1, as earlier predicted by Alois Mader and colleagues. The test consisted of each participant performing several constant-intensity running bouts of ≈ 30 min at intensities close to the estimated MLSS. During each run, we measured lactate every 5 min. Based on the results, we defined the MLSS as the "workload where the concentration of blood lactate does not increase more than 1 mmo.L- 1during the last 20 min of a constant load exercise". This MLSS protocol is impractical for performance testing as it requires too many exercise bouts, but it is a gold standard to determine the real MLSS. It is especially useful to validate indirect tests that seek to estimate the MLSS.

A longitudinal study on the interchangeable use of whole-body and local exercise thresholds in cycling

Purpose

This study longitudinally examined the interchangeable use of critical power (CP), the maximal lactate steady state (MLSS) and the respiratory compensation point (RCP) (i.e., whole-body thresholds), and breakpoints in muscle deoxygenation (m[HHb]_BP) and muscle activity (iEMG_BP) (i.e., local thresholds).

Methods

Twenty-one participants were tested on two timepoints (T1 and T2) with a 4-week period (study 1: 10 women, age = 27 ± 3 years, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{O}}_{{2{\text{peak}}}}$$\end{document}V˙O2peak = 43.2 ± 7.3 mL min⁻¹kg⁻¹) or a 12-week period (study 2: 11 men, age = 25 ± 4 years, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{O}}_{{2{\text{peak}}}}$$\end{document}V˙O2peak = 47.7 ± 5.9 mL min⁻¹ kg⁻¹) in between. The test battery included one ramp incremental test (to determine RCP, m[HHb]_BP and iEMG_BP) and a series of (sub)maximal constant load tests (to determine CP and MLSS). All thresholds were expressed as oxygen uptake (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{O}}_{2}$$\end{document}V˙O2) and equivalent power output (PO) for comparison.

Results

None of the thresholds were significantly different in study 1 (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{O}}_{2}$$\end{document}V˙O2: P = 0.143, PO: P = 0.281), but differences between whole-body and local thresholds were observed in study 2 (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{O}}_{2}$$\end{document}V˙O2: P < 0.001, PO: P = 0.024). Whole-body thresholds showed better 4-week test–retest reliability (TEM = 88–125 mL min⁻¹ or 6–10 W, ICC = 0.94–0.98) compared to local thresholds (TEM = 189–195 mL min⁻¹ or 15–18 W, ICC = 0.58–0.89). All five thresholds were strongly associated at T1 and T2 (r = 0.75–0.99), but their changes from T1 to T2 were mostly uncorrelated (r = − 0.41–0.83).

Conclusion

Whole-body thresholds (CP/MLSS/RCP) showed a close and consistent coherence taking into account a 3–6%-bandwidth of typical variation. In contrast, local thresholds (m[HHb]_BP/iEMG_BP) were characterized by higher variability and did not consistently coincide with the whole-body thresholds. In addition, we found that most thresholds evolved independently of each other over time. Together, these results do not justify the interchangeable use of whole-body and local exercise thresholds in practice.

Comparison of maximal lactate steady state with anaerobic threshold determined by various methods based on graded exercise test with 3-minute stages in elite cyclists

Background

The maximal lactate steady state (MLSS) is defined as the highest workload that can be maintained for a longer period of time without continued blood lactate (LA) accumulation. MLSS is one of the physiological indicators of aerobic performance. However, determination of MLSS requires the performance of a series of constant-intensity tests during multiple laboratory visits. Therefore, attempts are made to determine MLSS indirectly by means of anaerobic threshold (AT) evaluated during a single graded exercise test (GXT) until volitional exhaustion. The aim of our study was to verify whether AT determined by maximal deviation (D_max), modified maximal deviation (ModD_max), baseline LA concentration + 1 mmol/l (+ 1 mmol/l), individual anaerobic threshold (IAT), onset of blood lactate accumulation (OBLA_4mmol/l) and V-slope methods based on GXT with 3-min stages provide valid estimates of MLSS in elite cyclists.

Methods

Twelve elite male cyclists (71.3 ± 3.6 ml/kg/min) completed GXT (the increase by 40 W every 3 min) to establish the AT (by D_max, ModD_max, + 1 mmol/l, IAT, OBLA_4mmol/l and V-slope methods). Next, a series of 30-min constant-load tests to determine MLSS was performed. Agreement between the MLSS and workload (WR) at AT was evaluated using the Bland–Altman method.

Results

The analysis revealed a very high (r_s > 0.90, p < 0.001) correlation between WR_MLSS and WR_Dmax and WR_IAT. The other AT methods were highly (r_s > 0.70) correlated with MLSS except for OBLA_4mmol/l (r_s = 0.67). The Bland-Altman analysis revealed the highest agreement with MLSS for the D_max, IAT and + 1 mmol/l methods. Mean difference between WR_MLSS and WR_Dmax, WR_IAT and WR_+1mmol/l was 1.7 ± 3.9 W, 4.3 ± 7.9 W and 6.7 ± 17.2 W, respectively. Furthermore, the WR_Dmax and WR_IAT had the lowest limits of agreement with the WR_MLSS. The ModD_max and OBLA_4mmol/l methods overestimated MLSS by 31.7 ± 18.5 W and 43.3 ± 17.8 W, respectively. The V-slope method underestimated MLSS by 36.2 ± 10.9 W.

Conclusions

The AT determined by D_max and IAT methods based on the cycling GXT with 3-min stages provides a high agreement with the MLSS in elite cyclists. Despite the high correlation with MLSS and low mean difference, the AT determined by + 1 mmol/l method may highly overestimate or underestimate MLSS in individual subjects. The individual MLSS cannot be properly estimated by V-slope, ModD_max and OBLA_4mmol/l methods.

Effects of six-week sprint interval or endurance training on calculated power in maximal lactate steady state

The purpose of the study was to evaluate and compare the influence of sprint interval training (SIT) and endurance training (ET) on calculated power in maximal lactate steady state (PMLSS) (influenced by the maximal lactate production rate (⩒La_max) and maximal oxygen uptake (⩒O_2max)). Thirty participants were randomly assigned to the a) SIT, b) ET, or c) control group (n = 10 each). Each session consisted of four to six repetitions of 30 s all-out effort Wingate anaerobic tests (SIT) or 60 min cycling at 1.5 to 2.5 mmol∙L^-1 blood lactate (analysed every 10 min). Both groups performed training on three days per week, over a period of six weeks. To measure ⩒La_max and ⩒O_2max, and to calculate PMLSS, sprint and ramp tests were performed at baseline and after two, four and six weeks of intervention. While SIT resulted in a significant reduction of ⩒La_max (-0.08 ± 0.05 mmol∙L^-1∙s^-1, p=0.003) after two weeks and remained subsequently stable, ⩒O_2max (+2.6 ± 2.4 ml∙min^-1∙kg^-1, p = 0.044) and PMLSS (+25 ± 14 W, p=0.002) increased, but not before six weeks of SIT. After two weeks of ET, ⩒La_max remained unchanged, but ⩒O_2max increased by increased by +2.9 ± 2.4 ml∙min-1∙kg-1, p=0.03, and after six weeks by 5.6 ± 3.5 ml∙min^-1∙kg^-1. The increase of PMLSS was significant after four weeks of ET (+16 ± 14 W, p=0.036) and increased to +32 ± 17 W after six weeks. Comparison of SIT and ET revealed no significant differences for ⩒La_max, ⩒O_2max or PMLSS after six weeks. The control group remained stable in all parameters. In both exercising groups there was a significant improvement of the calculated PMLSS due to different influences of ⩒La_max and ⩒O_2max.

Metabolic and performance-related consequences of exercising at and slightly above MLSS

Exercising at the maximal lactate steady state (MLSS) results in increased but stable metabolic responses. We tested the hypothesis that even a slight increase above MLSS (10 W), by altering the metabolic steady state, would reduce exercise performance capacity. Eleven trained men in our study performed: one ramp-incremental tests; two to four 30-minute constant-load cycling exercise trials to determine the PO at MLSS (MLSS_p ), and ten watts above MLSS (MLSS_p+10 ), which were immediately followed by a time-to-exhaustion test; and a time-to-exhaustion test with no-prior exercise. Pulmonary O₂ uptake V.O₂ ) and blood lactate concentration ([La^- ]_b ) as well as local muscle O₂ extraction ([HHb]) and muscle activity (EMG) of the vastus lateralis (VL) and rectus femoris (RF) muscles were measured during the testing sessions. When exercising at MLSS_p+10 , although V.O₂ was stable, there was an increase in ventilatory responses and EMG activity, along with a non-stable [La^- ]_b response (P < 0.05). The [HHb] of VL muscle achieved its apex at MLSS_p with no additional increase above this intensity, whereas the [HHb] of RF progressively increased during MLSS_p+10 and achieved its apex during the time-to-exhaustion trials. Time-to-exhaustion performance was decreased after exercising at MLSS_p (37.3 ± 16.4%) compared to the no-prior exercise condition, and further decreased after exercising at MLSS_p+10 (64.6 ± 6.3%) (P < 0.05). In summary, exercising for 30 min slightly above MLSS led to significant alterations of metabolic responses which disproportionately compromised subsequent exercise performance. Furthermore, the [HHb] signal of VL seemed to achieve a "ceiling" at the intensity of exercise associated with MLSS.

A Two-test Protocol for the Precise Determination of the Maximal Lactate Steady State

The purpose of this study was to determine the efficacy of a two-test method for precisely identifying the Maximal Lactate Steady State (MLSS). Eight male competitive cyclists performed two bouts on a cycle ergometer. Following a maximal oxygen consumption (V̇O_2max) test (66.91 ± 5.29 mL·kg^-1·min^-1) we identified the lactate deflection point using the visual deflection (T_Vis), Log-Log (T_Log), D_max (T_Dmax), RER = 1.00 (T_RER), ventilatory threshold (T_Vent), and the 1.0 mmol·L^-1 increase above baseline (T₊₁) methods. The second incremental test (SIT) consisted of 6-7 stages (5 min each) starting 20-30 W below to 20-30 W above the predetermined deflection point, in 10 W increments. Comparison of the two tests yielded different threshold estimates (range 11-46W) for all methods (P = 0.001-0.019) except the T_Log (P = 0.194) and T_RER (P = 0.100). The SIT resulted in significantly (P = 0.007) more narrow range of thresholds (27.5 ± 11.01W) compared to the V̇O_2max test (70 ± 42.51W). The T_Vis from the SIT was identified as the MLSS and was verified using three 45-minute steady-state exercise bouts at 95%, 100%, and 105% of MLSS intensity (average increment 12.8 W). Blood lactate and V̇O₂ were recorded every 5 minutes and differed between the three intensities at every time point (P < 0.001). V̇O₂ increased from the 5^th to the 45^th minute by 7.02 mL·kg^-1·min^-1 (100% MLSS), 3.63 mL·kg^-1·min^-1 (95% MLSS) and 7.5 mL·kg^-1·min^-1 (105% MLSS, to the 30^th minute). These results indicate that the MLSS was identified correctly by the SIT, the single incremental test overestimated the MLSS intensity, and the T_Vis provides a very accurate determination of the lactate breakpoint. The use of a second submaximal test is required for a precise identification of MLSS.

Non-exhaustive double effort test is reliable and estimates the first ventilatory threshold intensity in running exercise

PURPOSE

The present study aimed to investigate the reliability of the non-exhaustive double effort (NEDE) test in running exercise and its associations with the ventilatory thresholds (VT₁ and VT₂) and the maximal lactate steady state (MLSS).

METHODS

Ten healthy male adults (age: 23 ± 4 years, height: 176.6 ± 6.4 cm, body mass: 76.6 ± 10.7 kg) performed 4 procedures: (1) a ramp test for VT₁ and VT₂ determinations measured by ratio of expired ventilation to O₂ uptake (VE/VO₂) and expired ventilation to CO₂ output (VE/VCO₂) equivalents, respectively; (2) the NEDE test measured by blood lactate concentration (NEDE_LAC) and heart rate responses (NEDE_HR); (3) a retest of NEDE for reliability analysis; and (4) continuous efforts to determine the MLSS intensity. The NEDE test consisted of 4 sessions at different running intensities. Each session was characterized by double efforts at the same running velocity (E1 and E2, 180 s), separated by a passive recovery period (90 s rest). LAC and HR values after E1 and E2 (in 4 sessions) were used to estimate the intensity equivalent to "null delta" by linear fit. This parameter represents, theoretically, the intensity equivalent to maximal aerobic capacity.

RESULTS

The intraclass correlation coefficient indicated significant reliability for NEDE_LAC (0.93) and NEDE_HR (0.79) (both p < 0.05). There were significant correlations, no differences, and strong agreement with the intensities predicted by NEDE_LAC (10.1 ± 1.9 km/h) and NEDE_HR (9.8 ± 2.0 km/h) to VT₁ (10.2 ± 1.1 km/h). In addition, despite significantly lower MLSS intensity (12.2 ± 1.2 km/h), NEDE_LAC and NEDE_HR intensities were highly correlated with this parameter (0.90 and 0.88, respectively).

CONCLUSION

The NEDE test applied to running exercise is reliable and estimates the VT₁ intensity. Additionally, NEDE intensities were lower but still correlated with VT₂ and MLSS.

Evaluation of efforts in untrained Wistar rats following exercise on forced running wheel at maximal lactate steady state

[Purpose]

We aimed to examine the effect of running speed on metabolic responses associated with maximal lactate steady state (MLSS) in rats during forced running wheel (FRW) exercise.

[Methods]

Forty male adult Wistar rats were divided into seven groups. The blood lactate threshold and peak running speed were determined for an incremental power test group. Five groups participated in constant power tests at intensities 10, 13, 14.5, 16, and 17.5 m/min to determine MLSS and a non-exercise group was chosen as the control. Animals were euthanized immediately after constant power tests and their corticosterone, non-esterified fatty acid (NEFA), blood glucose, and creatine kinase (CK) levels analyzed. The differences among groups were identified by one-way analysis of variance (p < 0.05).

[Results]

Blood lactate threshold corresponded a running intensity of 15 m/min, while MLSS was determined to be 16 m/min. Serum corticosterone concentrations were significantly higher in 14.5, 16, and 17.5 m/min groups (298.8±62, 338.3±65, and 354±26 nM, respectively) as compared to that in the control group (210.6±16 nM). Concentrations of NEFA observed in groups 13, 14.5, 16, and 17.5 m/min (662.8±24, 702.35±69, 718.4±34, and 752.8±77 μM, respectively) were significantly higher than those in 10 m/min and control groups (511.1±53 and 412.1±56 μM, respectively). The serum CK concentration recorded for group 17.5 m/min (372.4±56 U/L) was higher than those recorded for other groups.

[Conclusion]

The speed above 16 m/min on FRW resulted in increased physiological demands and muscle damage in untrained healthy Wistar rats.

Is the critical running speed related to the intermittent maximal lactate steady state?

The purpose of the present study was to compare the critical speed (CS) with the speed at the maximal lactate steady state (vMLSS) determined by a continuous and an intermittent model in trained runners. Eight male endurance runners (30.3 ± 10.6 years; 65.0 ± 8.5 kg; 1.73 ± 0.6 m; 11.3 ± 4.0% body fat) volunteered for this investigation and performed an incremental treadmill test, as well as 2-5 30-min constant speed tests to determine the MLSS continuous and MLSS intermittent (5 min of running, interspaced by 1 min of passive rest). The CS was determined by 2 maximal running efforts of 1500 and 3000 m performed on a 400 m running track. The CS was calculated as the slope of the linear regression of distance versus time. Statistical analysis revealed no significant difference between CS and MLSS determined by intermittent running (15.2 ± 1.0 km·h(-1) vs. 15.3 ± 0.7 km·h(-1), respectively), however, both were significantly higher than continuous MLSS (14.4 ± 0.6 km·h(-1)). There was also a significant correlation between CS and MLSS intermittent (r = 0.84, p = 0.008). On the basis of the present results, we conclude that for practical reasons (low cost, non-invasive) the CS is an interesting and alternative method to prescribe endurance interval training at maximal lactate steady state intensity, in preference to a continuous protocol.