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  • Author: Renate M. Leithäuser x
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Renate M. Leithäuser

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Renate M. Leithäuser

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Renate M. Leithäuser

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Ralph Beneke and Renate M. Leithäuser

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Ralph Beneke and Renate M. Leithäuser

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.

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Ralph Beneke, Renate M. Leithäuser and Oliver Ochentel

A link between lactate and muscular exercise was seen already more than 200 years ago. The blood lactate concentration (BLC) is sensitive to changes in exercise intensity and duration. Multiple BLC threshold concepts define different points on the BLC power curve during various tests with increasing power (INCP). The INCP test results are affected by the increase in power over time. The maximal lactate steady state (MLSS) is measured during a series of prolonged constant power (CP) tests. It detects the highest aerobic power without metabolic energy from continuing net lactate production, which is usually sustainable for 30 to 60 min. BLC threshold and MLSS power are highly correlated with the maximum aerobic power and athletic endurance performance. The idea that training at threshold intensity is particularly effective has no evidence. Three BLC-orientated intensity domains have been established: (1) training up to an intensity at which the BLC clearly exceeds resting BLC, light- and moderate-intensity training focusing on active regeneration or high-volume endurance training (Intensity < Threshold); (2) heavy endurance training at work rates up to MLSS intensity (Threshold ≤ Intensity ≤ MLSS); and (3) severe exercise intensity training between MLSS and maximum oxygen uptake intensity mostly organized as interval and tempo work (Intensity > MLSS). High-performance endurance athletes combining very high training volume with high aerobic power dedicate 70 to 90% of their training to intensity domain 1 (Intensity < Threshold) in order to keep glycogen homeostasis within sustainable limits.

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Philip Davis, Renate M. Leithäuser and Ralph Beneke

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.

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Ralph Beneke, Hermann Heck, Helge Hebestreit and Renate M Leithäuser

The value of blood lactate concentration (BLC) measured during incremental load tests in predicting maximal lactate-steady-state (MLSS) workload has rarely been investigated in children. In 17 children and 18 adults MLSS was 4.1 ± 0.9mmol 1.1. Workload at BLC of 3.0mmol 1.1 determined during an incremental load test explained about 80% of the variance (p < .001) and best predicted MLSS workload independent of age. This was despite the increase in power per time related to maximum incremental load test power being higher (p < .001) in children than in adults. The BLC response to given exercise intensities is faster in children without affecting MLSS.

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Ralph Beneke, Tobias G.J. Weber and Renate M. Leithäuser

Effects of different cycling cadences (revolutions/min [rpm]) on metabolic rate, blood lactate concentration (BLC), and reliance on carbohydrate (CHO) defined as the fraction of oxygen uptake used for CHO oxidation (relCHO) are highly individual. Whether this depends on the individually maximal achievable rpm obtained at minimized cycling resistance (rpmmax) is unknown. The authors tested the hypotheses that the individual freely chosen rpm in an incremental cycle-ergometer test (ILT) and relCHO at given BLC levels both depend on rpmmax. Seven master cyclists and 8 not specifically trained leisure athletes performed an ILT at individually freely chosen rpm and an rpmmax test. Respiratory data and BLC were measured; relCHO was plotted as a function of the BLC for the determinations of the individual BLC at relCHO of 75% and 95% (BLC75% and BLC95%). With 16.7%, the between-subjects variability of individual rpm was high but independent from rpmmax. In the master athletes, rpmmax explained 59.3% and 95.2% of BLC75% (P = .043) and BLC95% (P = .001), respectively. Irrespective of cycling experience, the individually preferred average rpm at submaximal stages of an ILT is highly variable and independent of rpmmax. In experienced cyclists, carbohydrate management defined as the ratio between substrate availability as indicated by BLC and relCHO depends on rpmmax.