Einfluss der Kurbelfrequenzen auf die Energiebereitstellung am maximalen Laktat-Steady State im Radsport
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Philipps-Universität Marburg
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Abstract
Introduction: In this study spiroergometry and blood lactate analysis were used
during various stress programs to investigate the influence of different crank
frequencies in cycling on energy supply and their performance under prolonged,
constant-workload conditions in the range of the maximal lactate steady state.
Furthermore, the influence of various different crank frequencies on the maximal
lactate steady state was examined. This has been discussed controversially in
previous studies. Another aspect investigated in this study was whether the
individual maximum achievable crank frequency influences the maximal lactate
steady state. It was assumed that at high crank frequencies in comparison to low
crank frequencies, more fast-twitch muscle fibers are recruited, so that a higher
increase of the blood lactate concentration was expected. As the prolonged,
constant-workload tests were just at the anaerobic threshold, no significant
difference between high and low crank frequencies was expected in terms of
energy supply and respiratory values during the test.
Methods: For this study, 12 male recreational athletes were recruited at the age
of 28.6 ± 2.1 years, who were in different training condition. The tests included 9 - 13 days of testing, with a break of at least 2 days between each test day and
test. By means of spiroergometry and blood lactate analysis, respiratory values
and blood lactate concentrations were determined. Two incremental endurance
tests until cardiopulmonary exhaustion were performed by each subject as well
as 6 - 10 tests which lasted 30 minutes at constant workload and a cadence of
50 and 100 revolutions per minute, respectively. The number of prolonged,
constant-workload tests was based on the tests required to determine the
individual maximal lactate steady state. Additionally, a sprint test with the highest
possible short-term crank frequency without brake resistor was performed to
determine the maximum crank frequency.
Results: At exercise intensities in the range of the maximum lactate steady state,
the respiratory values for oxygen uptake and the emission of carbon dioxide as
well as the relative carbohydrate oxidation became constant after a short time
and were independent of the pedal frequency. Only a rather low (82 % on
average) and an initial excess of relative carbohydrate oxidation, which is due to
a significantly higher activation constant in the emission of carbon dioxide at 100
compared to 50 revolutions per minute, was noticeable. The blood lactate
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concentration showed a significant difference over the entire length of the test. At
100, a significantly higher maximal lactate steady state was reached than at 50
revolutions per minute (6.0 ± 1.5 vs. 3.7 ± 1.2 mmol/l). No statistical correlation
between the maximum crank frequency and the maximal lactate steady state was
found.
Conclusion: These results confirm studies that have found an influence of the
crank frequency on blood lactate concentrations, as well as studies that have
shown that crank frequency related differences in respiratory values and the
relative carbohydrate oxidation decrease or are no longer detectable as the
workload increases. The reason for the initial increase in relative carbohydrate
oxidation and the significantly higher activation constant in the emission of carbon
dioxide at 100 compared to 50 revolutions per minute is not clear, but suggests
that there is a high potential for error in the derivation of expected respiratory
values in prolonged, constant-workload tests from incremental endurance test.
The rather low relative carbohydrate oxidation suggests that less carbohydrate
oxidation is carried out at the maximal lactate steady state than previously
assumed. The fact that no statistical correlation between the maximum crank
frequency and the maximal lactate steady state could be proven may be due to
individual coordination capability. Future research should therefore recruit a more
uniform group of probands. To clarify the cause of the significant difference in
lactate concentration between the different crank frequencies and the
conspicuous dynamics of relative carbohydrate oxidation, further prolonged,
constant-workload tests in the range of the maximal lactate steady state should
be performed, which additionally consider muscle biopsies and electromyography
measurements as well as blood lactate analysis. An influence of the blood flow,
which is differently elevated in accordance with the crank frequency, should be
investigated.
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Created: 2024Issued: 2024-12-09Updated: 2024-12-09
Faculty
Medizin
Publisher
Philipps-Universität Marburg
Language
ger
Data types
DoctoralThesis
Keywords
relative Kohlenhydratoxidation am maximalen Laktat-Steady-StaterelCHO at the maximal lactate steady state, cycling cadenceKurbelfrequenz im Radsport
DFG-subjects
MLSSCHOrelCHORPM
DDC-Numbers
610
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Granseyer, Marisa: Einfluss der Kurbelfrequenzen auf die Energiebereitstellung am maximalen Laktat-Steady State im Radsport. : Philipps-Universität Marburg 2024-12-09. DOI: https://doi.org/10.17192/z2024.0372.
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This item has been published with the following license: In Copyright