Renate M. Leithäuser

Maximal lactate-steady-state independent of performance.

PURPOSE 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. METHODS 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. RESULTS 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). CONCLUSIONS 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.

Cardiospecificity of the 3rd generation cardiac troponin T assay during and after a 216 km ultra-endurance marathon run in Death Valley

AbstractBackgroundThe reasons for the appearance of cardiacspecific troponin (cTnT) after strenuous exercise are unclear. The aim of the present study was to evaluate the cardiospecificity of the 3rd generation cardiac cTnT assay during and after an ultra-endurance race of 216 km at extreme environmental conditions in Death Valley.Study design and methodsWe measured serially cTnT, creatine kinase (CK), activity and mass of the isoenzyme MB of CK (CK-MBact and CK-MBmass), and myoglobin in 10 well-trained athletes before, repeatedly during and after the race.ResultsSix of 10 participants finished the race within a preset time of 60 hours. Postrace values of biochemical markers CK, CK-MBact, CKMBmass, and myoglobin were significantly increased compared to baseline (p<0.05). CK-MBact increased from (median (25th/ 75thpercentile) 12 (10/13) U/L to 72 (32/110) U/L, CK-MBmass from 3.9 (2.9/5.6) U/L to 65 (18/80) U/L and CK increased from median 136 (98/ 228) U/L to 3,570 (985/6,884) U/L respectively. Pre-race myoglobin was 27 (22/31) µg/l compared to 530 (178/657) µg/l after the run. One runner developed significant exercise-induced rhabdomyolysis with spontaneous recovery. cTnT values remained below the 99th percentile reference limit in all athletes including the runner who developed significant rhabdomyolysis (peak CK 27,951 U/L).ConclusionsStrenuous endurance exercise, even under extreme environmental conditions, does not result in structural myocardial damage in well-trained ultra-endurance athletes. We found no crossreactivity between cTnT and CK, neither in exercise-induced skeletal muscle trauma nor after rhabdomyolysis underscoring the excellent analytical performance of 3rd generation cTnT assay.

Effect of Test Interruptions on Blood Lactate during Constant Workload Testing

OBJECTIVE To determine whether repetitive test interruptions (TI) during constant load testing influence blood lactate concentration (BLC), maximal lactate steady state (MLSS), MLSS workload (P-MLSS), and relative MLSS intensity (Int-MLSS). METHODS Nineteen males participated in this study. In experiment A, 10 subjects (27.5 +/- 2.9 yr; 183.7 +/- 5.2 cm; 77.4 +/- 3.7 kg) performed 30-min constant load tests: one without TI, one with TI of 30 s, and one with TI of 90 s after every 5 min of cycling at a given workload. In experiment B, nine subjects (28.0 +/- 2.7 yr; 182.9 +/- 6.8 cm; 76.2 +/- 4.5 kg) performed 30-min constant load tests at different workloads until MLSS had been determined for all three TI protocols. RESULTS In experiment A, the BLC after 30 min net working time (BLC30) was higher (P < 0.001) without TI (6.0 +/- 1.3 mmol.l(-1)) than with TI of 30 s (4.9 +/- 1.4 mmol.l(-1)) or 90 s (4.5 +/- 1.1 mmol.l(-1)). The change in BLC during the final 20 min (DeltaBLC10-30) was greater (P < 0.01) without TI (1.2 +/- 1.0 mmol.l(-1)) than with TI of 30 s (0.2 +/- 0.7 mmol.l(-1)) or 90 s (-0.3 +/- 0.7 mmol.l(-1)). In experiment B, the MLSS was not affected, but P-MLSS and Int-MLSS were lower (P < 0.01) without TI (277.8 +/- 24.4W and 73.7 +/- 7.6%) than with TI of 30 s (300.4 +/- 30.4W and 79.2 +/- 8.0%) or 90 s (310.0 +/- 31.2W and 81.5 +/- 7.1%). Approximately 35% of the variance of BLC30 and DeltaBLC10-30, and 70% of the variance of P-MLSS and Int-MLSS were explained by TI duration (P < 0.001). CONCLUSIONS TI decreased BLC30 and DeltaBLC10-30 but has no effect on MLSS. Consequently, with TI, the MLSS is achieved at higher P-MLSS and Int-MLSS.

Maximal lactate steady state during the second decade of age.

Maximal lactate steady state (MLSS) presumably corresponds to the highest constant workload that can be performed by oxidative metabolism. The anaerobic and, to a minor extent, the oxidative metabolism have been reported to be affected by age. The second decade of life is the key period in the change in energy metabolism between children and adults. The aim of this study was to evaluate the effects of age on MLSS in 34 male subjects (age: 15.4 +/- 2.8 yr, range: 11-20 yr; height: 171.8 +/- 14.9 cm, range: 134-191 cm; body mass: 59.6 +/- 15.5 kg, range: 27-90 kg) performing an incremental load test to determine maximal workload and several constant load tests for MLSS measurement on a cycle ergometer. MLSS (4.2 +/- 0.7 mmol.l-1, range: 2.8 to 5.5 mmol.l-1) and MLSS intensity related to maximal workload (66.5 +/- 7.7%, range: 50-84%) were independent of age. MLSS heart rate (180.1 +/- 10.1 min-1, range: 156-208 min-1) decreased (P < 0.01) with increasing age, whereas absolute (157.2 +/- 54.8 W, range: 65-240 W) and relative MLSS workload (2.6 +/- 0.5 W.kg-1, range: 1.5 to 4.1 W.kg-1) and absolute (236.9 +/- 79.0 W, range: 100-350 W) and relative maximal workload (3.9 +/- 0.6 W.kg-1, range: 2.7 to 5.5 W.kg-1) increased (P < 0.001) with age. The age independence of MLSS supports the theory that neuromuscular factors may contribute to the frequently observed changes in response to given exercise with physical maturity more than changes in oxidative metabolism and/or glycolysis.

New Highly Sensitivity Assay Used to Measure Cardiac Troponin T Concentration Changes During a Continuous 216-km Marathon

We recently measured cardiac troponin T (cTnT)1 concentrations serially in blood from 10 participants of the Badwater ultramarathon, a continuous 216-km race that takes place under extreme environmental conditions. Details on the Badwater ultramarathon itself, and on the training experience and health condition of the athletes have been reported previously (1). Briefly, the athletes had completed a mean of 43.4 (median 20, range 5–130) marathons and 20.4 (median 15, range 6–80) ultramarathons, and the mean finishing times for the Badwater race were 51.24 h (median 45.2 h, range 43.5–61.4 h). cTnT was measured with a new highly sensitive assay for cardiac troponin T (Hs-TnT) (Roche Diagnostics) on an ELECSYS 2010 automated analyzer that uses chemiluminescence technology. As described previously (2), the interassay CV of this assay is 8% at 10 ng/L and 2.5% at 100 ng/L, and the intraassay CV is 5% at 10 ng/L and 1% at 100 ng/L. The diagnostic range of this assay is 2 to 10000 ng/L. Blood samples (EDTA plasma) were drawn at baseline, after …

The Energetics of Semicontact 3 x 2-min Amateur Boxing

UNLABELLED The energy expenditure of amateur boxing is unknown. PURPOSE Total metabolic cost (Wtot) as an aggregate of aerobic (Waer), anaerobic lactic (W[lactate]), and anaerobic alactic (WPCr) energy of a 3 × 2-min semicontact amateur boxing bout was analyzed. METHODS Ten boxers (mean ± SD [lower/upper 95% confidence intervals]) age 23.7 ± 4.1 (20.8/26.6) y, height 180.2 ± 7.0 (175.2/185.2) cm, body mass 70.6 ± 5.7 (66.5/74.7) kg performed a semicontact bout against handheld pads created from previously analyzed video footage of competitive bouts. Net metabolic energy was calculated using respiratory gases and blood [lactate]. RESULTS Waer, 526.0 ± 57.1 (485.1/566.9) kJ, was higher (P < .001) than WPCr, 58.1 ± 13.6 (48.4/67.8) kJ. W[lactate], 26.2 ± 7.1 (21.1/31.3) kJ, was lower (P < .001) than Waer and WPCr. An ~70-kJ fraction of the aerobic energy expenditure reflects rephosphorylation of high-energy phosphates during the breaks between rounds, which elevated Wtot to ~680 kJ with relative contributions of 77% Waer, 19% WPCr, and 4% W[lactate]. CONCLUSIONS The results indicate that the metabolic profile of amateur boxing is predominantly aerobic. They also highlight the importance of a highly developed aerobic capacity as a prerequisite of a high activity rate during rounds and recovery of the high-energy phosphate system during breaks as interrelated requirements of successful boxing.

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.

Maximal Lactate Steady State Depends on Cycling Cadence.

The maximal lactate steady state (MLSS) depicts the highest blood lactate concentration (BLC) that can be maintained over time without a continual accumulation at constant prolonged workload. In cycling, no difference in the MLSS was combined with lower power output related to peak workload (IMLSS) at 100 than at 50 rpm. MLSS coincides with a respiratory exchange ratio (RER) close to 1. Recently, at incremental exercise, an RER of 1 was found at similar workload and similar intensity but higher BLC at 100 than at 50 rpm. Therefore, the authors reassessed a potential effect of cycling cadences on the MLSS and tested the hypothesis that the MLSS would be higher at 105 than at 60 rpm with no difference in IMLSS in a between-subjects design (n = 16, age 25.1 ± 1.9 y, height 178.4 ± 6.5 cm, body mass 70.3 ± 6.5 kg vs n = 16, 23.6 ± 3.0 y, 181.4 ± 5.6 cm, 72.5 ± 6.2 kg; study I) and confirmed these findings in a within-subject design (n = 12, 25.3 ± 2.1 y, 175.9 ± 7.7 cm, 67.8 ± 8.9 kg; study II). In study I, the MLSS was lower at 60 than at 105 rpm (4.3 ± 0.7 vs 5.4 ± 1.0 mmol/L; P = .003) with no difference in IMLSS (68.7% ± 5.3% vs 71.8% ± 5.9%). Study II confirmed these findings on MLSS (3.4 ± 0.8 vs 4.5 ± 1.0 mmol/L; P = .001) and IMLSS (65.0% ± 6.8% vs 63.5% ± 6.3%; P = .421). The higher MLSS at 105 than at 60 rpm combined with an invariance of IMLSS and RER close to 1 at MLSS supports the hypothesis that higher cadences can induce a preservation of carbohydrates at given BLC levels during low-intensity, high-volume training sessions.

The Unsung Heroes in Science

National Science Standards • NS.5-8.7 HISTORY AND NATURE OF SCIENCE As a result of activities in grades 5-8, all students should develop understanding of o Science as a human endeavor o Nature of science o History of science • NS.9-12.7 HISTORY AND NATURE OF SCIENCE As a result of activities in grades 9-12, all students should develop understanding of o Science as a human endeavor o Nature of scientific knowledge o Historical perspectives

Top Sporting Events: Excitement, Media Presence, and Money—Winners and Losers at Various Levels

aaa This summer appears to be a particular busy one! It seems that one top sporting event follows another. Active sportsmen/women, coaches and support staff, and the interested spectators and viewers all need good stamina. The FIFA Football World Cup 2018 is a highlight—a tournament with an expected worldwide TV audience of more than 3.4 billion and an anticipated FIFA revenue reaching