Lactate Disappearance Research Articles

309 Evaluation of Encapsulated Megasphaera Elsdenii Ncimb 41125 in an Accelerated Beef Step-up Program and an Acidosis Challenge Model

Abstract A metabolism experiment was conducted to evaluate the effects of daily feeding of encapsulated Megasphaera elsdenii (M. elsdenii) NCIMB 41125 along with a one-time dose of Lactipro NXT (MS Biotec) on dry matter intake (DMI), rumen pH, in vitro lactate disappearance, volatile fatty acid (VFA) concentration, and lactate concentration. Ruminally cannulated crossbred steers (n = 40, initial BW 437 ± 98 kg) were individually fed a finisher diet consisting of 70% steam-flaked corn, 18% modified distillers grain plus soluble, and 7% alfalfa hay. Treatments were control (Con) steers which were given no M. elsdenii and four treatments that received LactiproNXT on day 1 and were given 0 (Drench), 1×106 (Low), 1×107 (Medium), or 1×108 (High) CFU of encapsulated M. elsdenii daily throughout the experiment fed as a top-dress. Adaptation to the finishing diet was accomplished in 19 days for Con steers and 9 days for steers in the Drench, Low, Medium, and High treatments. The experiment included five continuous periods: step-up (d 1-19); finishing (d 20-88); feed restriction (d 89, 24-h full feed restriction); challenge (d 90, cattle were fed at 150% of max DMI from finishing period); and recovery (d 91-94). Data were analyzed using the MIXED procedure of SAS with linear and quadratic effects of dose with drench as the intercept. There were no significant differences for DMI in the step-up, finishing, or challenge period. In the recovery period, DMI was greater for Low, Med, and High compared with Drench (P = 0.07) and there was a tendency for a linear increase in DMI with increasing the dose of M. elsdenii (P = 0.11). Recovery period DMI, expressed as a percentage of pre-challenge intake, was greater (P = 0.05) in steers fed M. elsdenii daily compared with Drench steers, and increased linearly (P = 0.06) as dose of M. elsdenii increased. Rumen pH in steers fed M. elsdenii daily was greater (P < 0.01) during the feeding period and tended to be greater during the challenge (P = 0.14) and recovery (P = 0.11) periods when compared with the Drench treatment. In vitro lactate disappearance tended to be greater (P = 0.13) in steers given M. elsdenii daily when compared with Con and Drench on d 88. For days 90, 91, and 92 combined, a treatment effect was observed for in vitro lactate disappearance with steers in the Low, Med, and High treatments having greater (P < 0.05) disappearance than Con steers, and Med steers having greater (P < 0.05) disappearance than all other treatments. An accelerated step up is possible with the drench and daily feeding of M. elsdenii. Daily feeding of M. elsdenii has a positive effect on cattle during and after an acidosis challenge event.

Lactate uptake in the rumen and its contributions to subacute rumen acidosis of goats induced by high-grain diets.

Rumen acidosis is the consequence of feeding rapidly fermentable grain diets and it is considered the most common nutritional disorder in intensive feeding ruminants. Due to that mechanism of catabolism and transformation is driven by multi-factors, the role of ruminal lactate and its contribution to subacute rumen acidosis has not been well defined yet. The aim of this study is to evaluate the effects of SARA on the production, absorption, circulation, and transformation of lactate in the rumen. In this study, rumen samples were collected from 12 adult Saanen goats (44.5 ± 4.6 kg BW) equipped with permanent rumen cannula to measure rumen fermentation parameters, organic acids production, microbial profiles, and blood indicators to identify the occurrence of SARA. To further investigate the change in the disappearance rate of ruminal lactate, rumen fluid was collected and a batch culture was performed. The results showed that the clearance rate of ruminal lactate was accelerated by SARA, and the concentration of the ruminal lactate pool was stable. In addition, the rumen liquid dilution rate and the rumen liquid flow rate under the SARA condition of goats were lower than that in normal conditions. The ruminal lactate flow rate had no difference throughout the process of fermentation. However, in vitro data showed that the disappearance of lactate was reduced in SARA. By measuring the conversion of sodium L-[3-13C]-lactate in batch culture, it was found that the percentage of lactate converted to propionate was significantly lower in the SARA treatment and 16.13% more lactate converted to butyrate under SARA condition. However, the percentage of lactate transformed into acetate and butyrate was significantly increased in the SARA treatment than that of control. The relative population of total protozoa count in SARA was significantly reduced, while the relative population of Lactobacillus fermentum, Streptococcus bovis, Butyrivibrio fibrisolvens, Megasphaera elsdenii, and Selenomonas ruminantium in the SARA treatment was significantly induced (p < 0.05). It is concluded that the transformation of lactate into butyrate may promote the development of SARA. These findings provide some references to the diet formulation for preventing SARA.

Direct Evidence for Intracellular Homeostasis in Mammalian Cells: Insulin-independent Glucose Metabolisms

In our previous study, carbonates, NaHCO3 and Na2CO3, influence glucose metabolism in vitro, using Py-3Y1-S2 rat fibroblast cells, and these compounds accelerate significantly glucose consumption. In the present study, the effects of the carbonates on glucose metabolism were examined to determine whether these effects are universal among different cell lines, VERO green monkey kidney cells, TE-13 human esophageal cancer cells, and HepG2 human cells. Glucose was completely converted to lactate, which disappeared gradually from the culture medium. However, the disappearance of lactate from the medium was independent of carbonates. The present study clarified that NaHCO3 and Na2CO3 directly regulate glucose metabolism among different cell lines via an insulin-independent pathway, that is, intracellular homeostasis.

567 Ruminal characteristics and feedlot performance of feedlot steers during accelerated step-up to high-concentrate diets using Lactipro Advance®

Megasphaera elsdenii(ME) is the principal lactate-utilizing bacterium in cattle adapted to concentrates, and is marketed commercially as a probiotic (Lactipro Advance, MS Biotec) to facilitate transition to high-grain diets. In this study, ruminal characteristics and feedlot performance were measured for steers adapted to a high-grain diet using a traditional 22-d step-up program (C), and for steers adapted over 10 d with the aid of ME fresh culture administered as an oral gavage (F), an oral gavage of rehydrated lyophilized culture (R), or R combined with lyophilized culture powder administered daily as a ration top-dress (D). Yearling steers (n = 435; initial BW = 408 ± 5 kg) were blocked by weight and randomly allocated to 64 concrete surfaced pens with 7 steers/pen and 16 pens/treatment. Step-up diets contained 40, 30, and 20% corn silage, and were followed by a finishing diet containing 10% corn silage and 90% concentrate. Ruminal fluid was obtained by rumenocentesis 26 h after steers received their first step-up diet, and inoculated into culture tubes containing lactate medium to determine differences in capacity for lactate metabolism over 24 h. Steers were fed once daily ad libitum for 156 d, then weighed, and transported 450 km to a commercial abattoir for harvest. Hot carcass weight and incidence of liver abscesses were determined at harvest and carcass traits were evaluated after 36 h of refrigeration. No differences were detected for feedlot performance (P>0.20), liver abscesses (P= 0.45), or carcass traits (P>0.20). Capacity for lactate utilization was increased with all forms of ME, as evidenced by increases in optical density (absorbance) of ME cultures, disappearance of lactate, and increase in butyrate production (P 0.01). In conclusion, steers dosed with ME can be stepped up to finishing diets in 10 d with no adverse effects on performance. a,b Means within a row without a common superscript letter are different, P < 0.05 a,b Means within a row without a common superscript letter are different, P < 0.05

Different recovery methods and muscle performance after exhausting exercise: comparison of the effects of electrical muscle stimulation and massage.

In this study we assessed the influence of the three different recovery interventions massage (MSG), electrical muscle stimulation (EMS), and passive rest (PR) on lactate disappearance and muscle recovery after exhausting exercise bouts. Twelve healthy male sport students participated in the study. They attended the laboratory on five test days. After measurement of O2max and a baseline Wingate test (WGb), the three recovery interventions were tested in random counterbalanced order. High intensity exercise, which consisted of six exhausting exercise bouts (interspersed with active recovery), was followed by MSG, EMS or PR application (24 minutes); then the final Wingate test (WGf) was performed. Lactate, heart rate, peak and mean power, rating of perceived exertion (RPE), and total quality of recovery (TQR) were recorded. In WGf mean power was significantly higher than in WGb for all three recovery modalities (MSG 6.29%, EMS 5.33%, PR 4.84% increase, p < 0.05), but no significant differences in mean and peak power were observed between the three recovery modes (p > 0.05). The heart rate response and the changes in blood lactate concentration were identical in all three interventions during the entire protocol (p = 0.817, p = 0.493, respectively). RPE and TQR scores were also not different among the three interventions (p > 0.05). These results provide further evidence that MSG and EMS are not more effective than PR in the process of recovery from high intensity exercise.

Fructose and glucose co-ingestion during prolonged exercise increases lactate and glucose fluxes and oxidation compared with an equimolar intake of glucose

When fructose is ingested together with glucose (GLUFRU) during exercise, plasma lactate and exogenous carbohydrate oxidation rates are higher than with glucose alone. The objective was to investigate to what extent GLUFRU increased lactate kinetics and oxidation rate and gluconeogenesis from lactate (GNG(L)) and from fructose (GNG(F)). Seven endurance-trained men performed 120 min of exercise at ≈60% VO₂max (maximal oxygen consumption) while ingesting 1.2 g glucose/min + 0.8 g of either glucose or fructose/min (GLUFRU). In 2 trials, the effects of glucose and GLUFRU on lactate and glucose kinetics were investigated with glucose and lactate tracers. In a third trial, labeled fructose was added to GLUFRU to assess fructose disposal. In GLUFRU, lactate appearance (120 ± 6 μmol · kg⁻¹ · min⁻¹), lactate disappearance (121 ± 7 μmol · kg⁻¹ · min⁻¹), and oxidation (127 ± 12 μmol · kg⁻¹ · min⁻¹) rates increased significantly (P < 0.001) in comparison with glucose alone (94 ± 16, 95 ± 16, and 97 ± 16 μmol · kg⁻¹ · min⁻¹, respectively). GNG(L) was negligible in both conditions. In GLUFRU, GNG(F) and exogenous fructose oxidation increased with time and leveled off at 18.8 ± 3.7 and 38 ± 4 μmol · kg⁻¹ · min⁻¹, respectively, at 100 min. Plasma glucose appearance rate was significantly higher (P < 0.01) in GLUFRU (91 ± 6 μmol · kg⁻¹ · min⁻¹) than in glucose alone (82 ± 9 μmol · kg⁻¹ · min⁻¹). Carbohydrate oxidation rate was higher (P < 0.05) in GLUFRU. Fructose increased total carbohydrate oxidation, lactate production and oxidation, and GNG(F). Fructose oxidation was explained equally by fructose-derived lactate and glucose oxidation, most likely in skeletal and cardiac muscle. This trial was registered at clinicaltrials.gov as NCT01128647.

Modelling the Blood Lactate Response to Maximal Short Term Exercise with Elevated Starting Levels

Recently a 3-parameter bi-exponential model was proposed (Beneke et al. 2005) as a means of calculating the blood lactate concentration (BLC) response to maximal short term exercise (MSE). It approximates an extravascular increase (A) of lactate generated by exercise metabolism during MSE, which is equivalent to the subsequent return to the pre-exercise lactate concentration, and two velocity constants describing the corresponding kinetics of the appearance (k1) and the disappearance (k2) of lactate into and out of the blood compartment. Conceptually the model requires warm up procedures that do not increase BLC at the start of exercise (BLC0) compared toresting conditions. PURPOSE: We developed a new 3-parameter bi-exponential model that considers an elevated BLC0, and analysed the effect of potential inappropriate application of the previous model on tests with elevated BLC0. METHODS: 9 subjects (26.9 ± 5.1 yrs, 1.83 ± 0.06 m, 80.7 ± 7.8 kg) performed 16 Wingate anaerobic Tests following a standardized warm up. RESULTS: BLC0 was elevated compared to pre warm up (1.5 ± 0.6 mmol l−1 vs. 1.0 ± 0.4 mmol l−1, p < 0.001). Compared to the new model, use of the original model decreased the explanation of the variance of the BLC response, k2 and the predicted time of the maximum BLC (96.7 ± 2.0 vs. 96.2 ± 2.0 %, 0.0252 + 0.007 vs. 0.0246 ± 0.07 min−1 and 6.0 ± 1.0 vs. 5.8 ± 0.9 min; all p < 0.001). Both, A and k1 increased (15.2 ± 1.5 vs. 15.6 ± 1.6 mmol l−1 and 0.56 ± 0.13 vs. 0.59 ± 0.14 min−1; both p < 0.001) whilst the predicted post-test maximum BLC was not different (14.5 ± 1.6 vs. 14.5 ± 1.6 mmol l−1; p > 0.05). CONCLUSION: The results indicate that inappropriate application of the original model on tests with elevated starting BLC levels results in a misinterpretation of the dynamics of the BLC response to MSE but the predicted post- test maximum BLC remains unaffected.

Intensity of exercise recovery, blood lactate disappearance, and subsequent swimming performance

The aim of this study was to examine the effects of active versus passive recovery on blood lactate disappearance and subsequent maximal performance in competitive swimmers. Fourteen male swimmers from the University of Virginia swim team (mean age 20.3 years, s = 4.1; stature 1.85 m, s = 2.2; body mass 81.1 kg, s = 5.6) completed a lactate profiling session during which the speed at the lactate threshold (VLT), the speed at 50% of the lactate threshold (VLT.5), and the speed at 150% of the lactate threshold (VLT1.5) were determined. Participants also completed four randomly assigned experimental sessions that consisted of a 200-yard maximal-effort swim followed by 10 min of recovery (passive, VLT.5, VLT, VLT1.5) and a subsequent 200-yard maximal effort swim. All active recovery sessions resulted in greater lactate disappearance than passive recovery (P < 0.0001 for all comparisons), with the greatest lactate disappearance associated with recovery at VLT (P = 0.006 and 0.007 vs. VLT.5 and VLT1.5 respectively) [blood lactate disappearance was 2.1 mmol · l−1 (s = 2.0), 6.0 mmol · l−1 (s = 2.6), 8.5 mmol · l−1 (s = 1.8), and 6.1 mmol · l−1 (s = 2.5) for passive, VLT.5, VLT, and VLT1.5 respectively]. Active recovery at VLT and VLT1.5 resulted in faster performance on time trial 2 than passive recovery (P = 0.005 and 0.03 respectively); however, only active recovery at VLT resulted in improved performance on time trial 2 (TT2) relative to time trial 1 (TT1) [TT2−TT1: passive +1.32 s (s = 0.64), VLT.5+1.01 s (s = 0.53), VLT−1.67 s (s = 0.26), VLT1.5−0.07 s (s = 0.51); P < 0.0001 for VLT). In conclusion, active recovery at the speed associated with the lactate threshold resulted in the greatest lactate disappearance and in improved subsequent performance in all 14 swimmers. Our results suggest that coaches should consider incorporating recovery at the speed at the lactate threshold during competition and perhaps during hard training sessions.

Modelling the lactate response to short-term all out exercise

BackgroundThe maximum post exercise blood lactate concentration (BLCmax) has been positively correlated with maximal short-term exercise (MSE) performance. However, the moment when BLCmax occurs (TBLCmax) is rather unpredictable and interpretation of BLC response to MSE is therefore difficult.MethodsWe compared a 3- and a 4-parameter model for the analysis of the dynamics of BLC response to MSEs lasting 10 (MSE10) and 30 s (MSE30) in eleven males (24.6 ± 2.3 yrs; 182.4 ± 6.8 cm; 75.1 ± 9.4 kg). The 3-parameter model uses BLC at MSE-start, extra-vascular increase (A) and rate constants of BLC appearance (k1) and disappearance (k2). The 4-parameter model includes BLC at MSE termination and amplitudes and rate constants of increase (A1, y1) and decrease (A2, y2) of post MSE-BLC.ResultsBoth models consistently explained 93.69 % or more of the variance of individual BLC responses. Reduction of the number of parameters decreased (p < 0.05) the goodness of the fit in every MSE10 and in 3 MSE30. A (9.1 ± 2.1 vs. 15.3 ± 2.1 mmol l-1) and A1 (7.1 ± 1.6 vs. 10.9 ± 2.0 mmol l-1) were lower (p < 0.05) in MSE10 than in MSE30. k1 (0.610 ± 0.119 vs. 0.505 ± 0.107 min-1), k2 (4.21 10-2 ± 1.06 10-2 vs. 2.45 10-2 ± 1.04 10-2 min-1), and A2 (-563.8 ± 370.8 vs. -1412.6 ± 868.8 mmol l-1), and y1 (0.579 ± 0.137 vs. 0.489 ± 0.076 min-1) were higher (p < 0.05) in MSE10 than in MSE30. No corresponding difference in y2 (0.41 10-2 ± 0.82 10-2 vs. 0.15 10-2 ± 0.42 10-2 min-1) was found.ConclusionThe 3-parameter model estimates of lactate appearance and disappearance were sensitive to differences in test duration and support an interrelation between BLC level and halftime of lactate elimination previously found. The 4-parameter model results support the 3-parameter model findings about lactate appearance; however, parameter estimates for lactate disappearance were unrealistic in the 4-parameter model. The 3-parameter model provides useful information about the dynamics of the lactate response to MSE.

Effect Of Sprint Duration On Blood Lactate Kinetics In Children, Adolescents And Adults

A lower blood lactate concentration (BLC) response to maximal short-term high intensity exercise has been consistently reported in children compared to both adolescents and adults. Therefore, it has been proposed that pre pubertal children have a lower glycolytic rate compared with adolescents and adults. PURPOSE: The aim of the present study was to examine the effect of age on changes in BLC and rate of muscular lactate appearance (MLAR) as an indicator of net glycolytic rate under real track sprinting conditions of given durations. METHODS: 8 pre-pubertal boys (age: 10.4±0.3 yrs, height: 1.42±0.09 m, body mass: 36.1±9.7 kg) and 9 male adolescents (15.4±0.3 yrs height: 1.71±0.04m, body mass: 61.2±7.3 kg) and 8 male adults (20.6±0.7 yrs height: 1.81±0.03 m, body mass: 83.9±14.9kg) completed 3 maximal sprints: duration T1: 100m, 150m and 150m; T2: 140m. 190m and 210m and T3: 200m, 260m and 280m for children, adolescents and adults, respectively. BLC was measured pre-exercise and up to 30 minutes post-exercise. Data were analysed using a bi-exponential 4-parameter model including lactate increases in the extravascular space (A) and time constants describing the appearance and disappearance of lactate in the blood compartment. MLAR was calculated based on A and generally accepted assumptions of water space and relative muscle mass in children and adolescents. RESULTS: Test duration was not different (P>0.05) between the groups for each sprint (T1: 18.9±3.4vs. 21.6±2.1 vs. 21.8±1.2;T2: 27.7±5.1 vs. 28.2±2.6vs. 32.2±3.8;T3: 42.8±8.9vs. 42.0±3.1 vs. 45.4±2.8 s). There was a significant main effect for maximum BLC with respect to sprint duration and age (p < 0.05). However, no group difference in MLAR was found (P>0.05). MLAR decreased (p < 0.05) with each increase in sprint duration (T1: 0.91±0.21 vs. 0.99±0.24vs. 1.0±0.24; T2: 0.69±0.19vs. 0.83±0.27vs. 0.92±0.23;T3:0.56±0.21 vs. 0.56±0.12 vs. 0.70±0.14 mmol.kg-1.s-1) irrespective of age. CONCLUSIONS: The results demonstrate that in flat out sprints lasting approx. 20 to 45 s, age influences the magnitude of the post-exercise BLC as result of relative muscle mass and dilution space without relevant differences in muscular glycolytic rate.

IS CHILDREN’S FASTER RECOVERY FROM EXERCISE DUE TO A HIGHER METABOLITE CLEARANCE RATE?

Dear Editor-in-Chief: We are writing regarding a recent article by Zafeiridis et al. (5), comparing recovery from high-intensity exercise in boys, adolescents, and adults. A faster recovery of performance capacity (knee flexion/extension) was demonstrated in children and adolescents compared with adults. It was concluded that recovery rate was maturity dependent. While the study and its results are well presented, we believe there is a significant discussion oversight regarding the mechanisms underlying this phenomenon. The authors speculate that a possible explanation may be a higher metabolite (lactate, H+) clearance rate in children: “Based on these facts, the possibility that the boys and teens in the current study had faster removal of lactate that facilitated the recovery process should not be excluded” (p. 511). The authors failed to consider the experimental evidence that contradicts their explanation. We addressed this very issue in a paper by Dotan et al. (1), which demonstrated, that blood lactate (La) disappearance rate following high-intensity exercise, is strikingly similar in children and adults, despite markedly different peak values ([La]peak). It was shown that not only was children’s La-disappearance half-time similar to that of adults, but that there was no difference between their La-recovery curves following similar [La]peak values. The only consistent difference being children’s shorter lag time to [La]peak. Therefore, it was argued that faster recovery in children is not due to a more efficient metabolite clearance rate, but rather to the fact that they have less to recover from (lower power output and La production) and that their [La]peak is reached sooner. The evidence of children’s lower sympathetic activation (3) that Zafeiridis et al. (5) cite in support of their view only supports our notion that children are anaerobically inferior, precisely because they are unable to fully mobilize their sympathetic system and recruit higher hierarchy motor units. This would explain their lower La production but not a faster La clearance. This is not to exclude other factors that separate boys from men (e.g., faster phosphocreatine resynthesis (2,4)). However, future research may well demonstrate that many or all of these differences stem from the alleged maturation-related difference in recruitment potential. Bareket Falk Raffy Dotan Brock University, Department of Physical Education and Kinesiology, St. Catharines, Ontario, Canada

Effects Of Exercise Recovery Intensity On Blood Lactate Disappearance And Subsequent Swimming Performance

Purpose During competition, swimmers are often faced with multiple races in a single day. It has become common practice during meets for swimmers to use active recovery between events in an attempt to facilitate improved performance. Thus, we examined the effects of active versus passive recovery on blood lactate disappearance and subsequent maximal performance in competitive swimmers. Methods Fourteen competitive swimmers completed a lactate profiling session during which the velocity at the lactate threshold (VLT), the velocity at 50% of the LT (VLT.5), and the velocity at 150% of the LT (VLT1.5) were determined. This involved 7 graded incremental 200 meter (m) freestyle swims with the first swim target time being 30 seconds slower than the individuals best 200 m time. Subsequent bouts had swim times that were 5 seconds faster than the previous swim target time with 5 minutes allotted for each stage. Blood was sampled from the ear or finger and immediately analyzed for lactate with an Accutrend portable lactate analyzer. Subjects also completed four randomly assigned experimental sessions that consisted of a 200 m maximal effort swim followed by 10 minutes of recovery (passive, VLT.5, VLT, VLT1.5) and a subsequent 200 m maximal effort swim. Swimmers swam their competitive stroke during the 200 m maximal effort swims and recovered using freestyle. Results All the active recovery sessions resulted in greater lactate disappearance compared to passive recovery (p<0.05) with the greatest lactate disappearance associated with recovery at VLT (p<0.05) (blood lactate concentrations prior to the second time trial were 7.1 ± 0.7, 4.0 ± 0.4, 3.1 ± 0.3, and 3.8 ± 0.5 mM for passive, VLT.5, VLT, and VLT1.5 respectively). Active recovery at VLT and VLT1.5 resulted in faster performance on time trial 2 compared to passive recovery (p<0.05), however only active recovery at VLT resulted in improved performance on time trial 2 relative to time trial 1 (T2 – T1 = 1.32 ± 0.64, 1.01 ± 0.53, −1.67 ± 0.26, and −0.07 ± 0.51 seconds for passive, VLT.5, VLT, and VLT1.5 recovery, respectively, p<0.05). Conclusion Active recovery at the velocity associated with the lactate threshold resulted in the greatest lactate disappearance and in improved subsequent performance in all 14 swimmers. These data suggest that coaches should consider incorporating recovery at VLT during competition and perhaps during hard training sessions.

4-parameter Model To Analyse The Blood Lactate Response To Short-term All-out Exercise

After the termination of maximal short-term high intensity exercise (MSE), the blood lactate concentration (BLC) continues to increase before it starts to decreases, a kinetic based on different dynamic physiological processes. Since the early 1980s the only tool for the non-invasive analysis of the latter is a bi-exponential 6-parameter model, which requires subsequent post-exercise BLC measurements for up to 120 min of rest. PURPOSE To analyse a 4-parameter model describing the BLC response to MSE that requires post-exercise BLC measurements for only 20 min with special respect to MSE-duration. METHODS 11 males (24.6 ± 2.3 yrs; 182.4 ± 6.8 cm; 75.1 ± 9.4 kg) performed MSE lasting 10 s (T1), 30 s (T2) and approx. 3 min (T3), respectively, with BLC measurements immediately before and up to 20 minutes post exercise. The model includes the BLC before exercise, a hypothetical exercise induced intra muscular increase of lactate (A), time constants describing the appearance (k1) and the disappearance (k2) of lactate in the blood compartment. Additionally, it enables to calculate the maximum of the BLC post MSE (BLCmax) and the time when BLCmax occurs (TBLCmax). RESULTS The explanation of variance of the BLC was 97 ± 2% (T1), 98 ± 2% (T2) and 99 ± 1% (T3), respectively. The mechanical energy (T1: 100.6 ± 9.8, T2: 248.0 ± 21.5, T3: 905.5 ± 112.5 J kg−1), A (T1: 9.0 ± 2.1, T2: 14.7 ± 2.1, T3: 19.1 ± 3.3 mmol l−1), BLCmax (T1: 8.6 ± 1.8, T2: 14.1 ± 1.8, T3: 15.1 ± 1.3 mmol l−1) and TBLCmax (T1: 4.4 ± 0.9, T2: 6.1 ± 1.0, T3: 8.7 ± 1.5 min) increased (p <0.05) whilst power output (T1: 10.1 ± 1.0, T2: 8.3 ± 0.7, T3: 4.8 ± 0.5 W kg−1) and k1 (T1: 0.733 ± 0.244, T2: 0.614 ± 0.164, T3: 0.313 ± 0.12 min−1) decreased (p <0.05) from T1 to T2 to T3, respectively. k2 was higher (p <0.05) in T1 (4.05 10−2 ± 1.12 10−2 min−1) than in T2 (2.08 10−2 ± 1.64 10−2 min−1). CONCLUSIONS The 4-parameter model appears to be suitable to analyse the dynamic pattern of the BLC response to MSE. All parameters proved to be sensitive with respect to changes in test duration and corresponding modulations in the exercise intensity. The model seems to provide useful information with respect to the lactate concentration in the blood, in the muscle, and the dynamics of the lactate exchange between both compartments.

Effects Of Exercise Recovery Intensity On Blood Lactate Disappearance And Subsequent Swimming Performance

Effects Of Exercise Recovery Intensity On Blood Lactate Disappearance And Subsequent Swimming Performance

Effect of Combined Active Recovery from Supramaximal Exercise on Blood Lactate Disappearance in Trained and Untrained Man

The purpose of this study was to determine the effect of different modalities of individualized active recovery on blood lactate disappearance after supramaximal exercise in subjects with different levels of aerobic fitness. Fourteen healthy subjects (7 trained and 7 untrained subjects mean age 20 +/- 1.5 and 19.5 +/- 1.5, respectively) participated in this study. They performed three supramaximal intermittent exercises at 60 % of the time to exhaustion at 120 % of the maximum aerobic power (MAP) with 5-min recovery periods (2 x 5 min). The third exercise was followed by 20 min of recovery. The effects of four types of recovery were compared in trained and untrained subjects: passive recovery (PR), an active recovery at an intensity corresponding to the first anaerobic ventilatory threshold minus 20 % (VT1), an active recovery at an intensity corresponding to the second anaerobic ventilatory threshold minus 20 % (VT2) and a combined active recovery (CR) which consisted of 7 min at VT2 followed by 13 min at VT1. Blood lactate levels were measured at rest and during the recovery periods. Peak blood lactate after supramaximal exercise was observed significantly earlier with VT2 and CR (4th min) than VT1 and PR (7th min) in trained and in untrained subjects. Combined active recovery (CR) showed a significantly faster lactate disappearance than did PR, VT1, or VT2 from the 7th min of recovery in trained subjects (p < 0.05) and at the 20th min in untrained subjects (p < 0.05). CR and VT2 conditions showed earlier peak blood lactate (4th min) than PR or VT1 (7th min). Blood lactate disappearance was faster in trained than untrained subjects during combined active recovery. This result suggests that the level of physical fitness plays an important role mainly in the pattern of blood lactate decrease during combined active recovery.

Cortisol response of green sturgeon to acid-infusion stress

Cortisol and lactate are classic indicators of stress in fishes and their interactive effects on metabolism during recovery from stress have recently become a subject of more intense study. We examined how stressing green sturgeon through acid infusion affected the cortisol response and lactate metabolism in green sturgeon ( Acipenser medirostris). Both lactic acid (0.3 M) and HCl (0.3 N) infusion (infusion volumes 1.5 ml kg −1) elicited an immediate cortisol response (21.61±4.61 ng ml −1 and 17.50±3.00 ng ml −1, respectively). Lactic acid prolonged the cortisol response compared to HCl (90 min vs. 25 min). Neutralized lactate (0.23 M; with 1 N NaOH; final pH 7.8) and NaCl (0.9%) infusion (infusion volumes 1.5 ml kg −1) did not affect plasma cortisol. Sturgeon infused with lactic acid showed a faster rate of lactate disappearance from plasma than those with neutralized lactic acid. We relate these findings to lactate metabolism following exercise, acid-infusion and air immersion stress in fishes.

Experiment and computer-aided simulation: complementary tools to understand exercise metabolism.

During the last two decades the concept of the MLSS (maximal lactate steady state) has been established. The MLSS detects the highest level of the BLC (blood lactate concentration) and the corresponding workload (MLSS workload) that can be maintained over time without continual BLC accumulation. In spite of a lack of experimental and/or theoretical foundation, it has been speculated that the level of the MLSS may decrease with increasing performance capacity. The potential inter-relationship between performance capacity and BLC response to prolonged constant workload will be analysed based on a recent study, which provided evidence that the MLSS is independent of performance whereas MLSS workload increases with performance capacity, and by a computer-aided simulation. The simulated model modifies and combines previous theories put forward to explain the response of BLC to exercise and incorporates a theory about limiting factors of oxygen transport to the muscle cell. Simulations consider the BLC response to selected prolonged constant workloads while paying special respect to changes in body structure and substrate utilization, which are generally accepted as limiting factors of performance capacity. This complex modulation of appearance and disappearance of lactate during constant prolonged exercise seems to support the experimental results, which indicated independence between MLSS and performance capacity.

PLASMA LACTATES AFTER 5KM TIME TRIALS REMAIN ELEVATED AND CORRELATE WITH % SLOW TWITCH FIBRES

A 5 km cycling time trial (TT) demands high, sustained muscle power output and substantial oxidative and glycolytic energy delivery. The aims of this study were to determine the effects of fibre type and muscle oxidative capacity on TT performance and post-TT plasma lactate accumulation. 12 endurance trained cyclists with average speeds for a recent 105 km race of between 31.5 and 37.7 km/h were tested for laboratory exercise performance (peak sustained power output (PPO) and 2 × TT: TT1 and TT2), plasma lactate accumulation (before, during and after TT2) and skeletal muscle composition (% myosin heavy chain isoform content (MHC) and citrate synthase (CS) activity). The coefficient of variation for TT1 and TT2 was 0.6%. We therefore used the mean of TT1 and TT2 to determine TTm. PPO was 345.6 ± 32.7 W and average speed for TTm was 41.2 ± 1.4 km/h (average test duration: 7 min 16 s ± 15 s). %MHCI was 58.1 ± 10.9 and %MHCIIa was 41.5 ± 11 (one subject had 12% MHCIIx). CS activity was 83.9 ± 9.4 umol/g d.w./min. Plasma lactate concentration (LACT) was 13.9 ± 1.4 mmol/L at 2 min post-TT2. By 20 min post-TT2, LACT was still 9.6 ± 2.3 mmol/L. TTm correleated with PPO (r = 0.59, P < 0.05) but not 105 km performance or CS activity. Neither TTm, nor CS activity correlated with LACT at any time point, or LACT area under the curve (AUC) or plasma lactate disappearance rate from 2 to 20 min post-TT2. But %MHCI correlated with LACT at the end of TT2 (r = 0.76, P < 0.01) and with AUC from the start of TT2 to 20 min. of recovery (r = 0.57, P < 0.05). Since LACT remained high for 20 minutes following TT2 when lactate production itself had ceased, we concluded that lactate release from the muscle was prolonged due to saturation of the transport proteins, MCT1 and MCT4. Since muscle oxidative capacity was unrelated to plasma lactate disappearance rate during recovery, we conclude that prolonged high levels of muscle lactate release overshadowed any influence of plasma lactate disappearance and subsequent oxidation on plasma lactate concentration itself. In this study, higher muscle lactate release in vivo, as indicated by higher post-exercise plasma lactate concentrations, was related to a higher percentage of slow twitch fibers. Sarcolemmal vesicle lactate transport capacity in vitro has previoulsy been shown to correlate with % slow twitch fibers (Pilegaard et al. J. Appl. Physiol. 77:1858–1862, 1994). Sponsor: Medical Research Council of South Africa.

Maximal lactate-steady-state independent of performance.

The maximal lactate steady state (MLSS) corresponds to the highest workload that can be maintained over time without a continual blood lactate accumulation. MLSS and MLSS intensity have been speculated to depend on performance. Experimental proof of this hypothesis is missing. 33 male subjects (age: 23.7 +/- 5.5 yr, height: 181.2 +/- 5.3 cm, body mass: 73.4 +/- 6.4 kg) performed an exhausting incremental load test to measure peak workload and three to six 30-min constant load tests on a cycle ergometer to determine MLSS. MLSS (4.9 +/- 1.4 mmol x L(-1)) was independent of MLSS workload (3.4 +/- 0.6 W x kg(-1)) and peak workload (4.8 +/- 0.6 W x kg(-1)). MLSS intensity (71.1 +/- 6.7%) did not correlate with peak workload or MLSS (P > 0.05). A positive correlation was found between peak workload and MLSS workload (r = 0.82, P < 0.001). MLSS and MLSS intensity are independent of performance but subjects with higher maximum performance have higher MLSS workloads. The combination of various fitness related effects on both, the production and the disappearance of lactate during exercise, may explain that different MLSS workloads coincide with similar levels of MLSS and MLSS intensity.

Lactate kinetics at rest and during exercise in lambs with aortopulmonary shunts.

In a previous study [G. C. M. Beaufort-Krol, J. Takens, M. C. Molenkamp, G. B. Smid, J. J. Meuzelaar, W. G. Zijlstra, and J. R. G. Kuipers. Am. J. Physiol. 275 (Heart Circ. Physiol. 44): H1503-H1512, 1998], a lower systemic O2 supply was found in lambs with aortopulmonary left-to-right shunts. To determine whether the lower systemic O2 supply results in increased anaerobic metabolism, we used [1-13C]lactate to investigate lactate kinetics in eight 7-wk-old lambs with shunts and eight control lambs, at rest and during moderate exercise [treadmill; 50% of peak O2 consumption (VO2)]. The mean left-to-right shunt fraction in the shunt lambs was 55 +/- 3% of pulmonary blood flow. Arterial lactate concentrations and the rate of appearance (Ra) and disappearance (Rd) of lactate were similar in shunt and control lambs, both at rest (lactate: 1, 201 +/- 76 vs. 1,214 +/- 151 micromol/l; Ra = Rd: 12.97 +/- 1.71 vs. 12.55 +/- 1.25 micromol. min-1. kg-1) and during a similar relative workload. We found a positive correlation between Ra and systemic blood flow, O2 supply, and VO2 in both groups of lambs. In conclusion, shunt lambs have similar lactate kinetics as do control lambs, both at rest and during moderate exercise at a similar fraction of their peak VO2, despite a lower systemic O2 supply.