Abstract
Introduction:
Indirect calorimetry is known to be a valid and reliable indicator for estimating fat and carbohydrate (CHO) oxidation utilisation rates. Lactate indicates the glycolytic activity, and its concentration in blood (BLC) is a standard measure of exercise intensity. The breakdown of carbohydrate via glycolysis results in pyruvate, which is either aerobically combusted or converted into lactate. The relative rate of pyruvate combustion (RPY) is determined by pyruvate dehydrogenase complex activity (PDH) in which pyruvate availability is a key regulator. Nevertheless, the ratio between lactate and pyruvate is regulated by the near equilibrium enzyme lactate dehydrogenase (LDH). Consequently, lactate may be used as an indicator of RPY. Consequently, lactate may be used as an indicator of RPY. Sigmoid approximations have previously been used to describe the behaviour of many metabolic systems including the relationship between lactate and pyruvate combustion. The study tested whether RPY can be described as a function of BLC in incremental exercise testing.
Methods:
21 healthy males (Age 26.3±6.0 years, Height 179.4±8.1 cm, Body mass 74.9±12.5 kg) followed an incremental cycling test at 50 rpm. Oxygen uptake (VO2) and carbon dioxide production (VCO2) were measured. Workload initiated with 1 W.kg-1 BM, and increased by 0.5 W.kg-1 BM every 2 min stage. CHO and fat oxidation using indirect calorimetry. The relative rate of pyruvate combustion (RPY) was calculated as a percentage of the full pyruvate combustion which is considered as when VO2 equals VCO2. RPY was further approximated as a sigmoid function of lactate (RPY = 100 / (1+kel / BLC2) where kel is the constant of half maximal pyruvate combustion.
Results:
Describing RPY as a function of BLC explained 86 ± 0.09% of the variance in RPY. Estimates of kel were 1.82±0.95 (mmol.l-1)2, and ranged from 0.54 to 4.4 (mmol.l-1)2. RPY appears more or less saturated at 96.5 ± 8.1% corresponding with BLC levels of 4.9±2.0 mmol.l-1.
Conclusion:
RPY may be described as a function of BLC. This may be useful in using BLC to explain the inter-individual variations in the relative utilisation of carbohydrate and fat during incremental exercise.
Indirect calorimetry is known to be a valid and reliable indicator for estimating fat and carbohydrate (CHO) oxidation utilisation rates. Lactate indicates the glycolytic activity, and its concentration in blood (BLC) is a standard measure of exercise intensity. The breakdown of carbohydrate via glycolysis results in pyruvate, which is either aerobically combusted or converted into lactate. The relative rate of pyruvate combustion (RPY) is determined by pyruvate dehydrogenase complex activity (PDH) in which pyruvate availability is a key regulator. Nevertheless, the ratio between lactate and pyruvate is regulated by the near equilibrium enzyme lactate dehydrogenase (LDH). Consequently, lactate may be used as an indicator of RPY. Consequently, lactate may be used as an indicator of RPY. Sigmoid approximations have previously been used to describe the behaviour of many metabolic systems including the relationship between lactate and pyruvate combustion. The study tested whether RPY can be described as a function of BLC in incremental exercise testing.
Methods:
21 healthy males (Age 26.3±6.0 years, Height 179.4±8.1 cm, Body mass 74.9±12.5 kg) followed an incremental cycling test at 50 rpm. Oxygen uptake (VO2) and carbon dioxide production (VCO2) were measured. Workload initiated with 1 W.kg-1 BM, and increased by 0.5 W.kg-1 BM every 2 min stage. CHO and fat oxidation using indirect calorimetry. The relative rate of pyruvate combustion (RPY) was calculated as a percentage of the full pyruvate combustion which is considered as when VO2 equals VCO2. RPY was further approximated as a sigmoid function of lactate (RPY = 100 / (1+kel / BLC2) where kel is the constant of half maximal pyruvate combustion.
Results:
Describing RPY as a function of BLC explained 86 ± 0.09% of the variance in RPY. Estimates of kel were 1.82±0.95 (mmol.l-1)2, and ranged from 0.54 to 4.4 (mmol.l-1)2. RPY appears more or less saturated at 96.5 ± 8.1% corresponding with BLC levels of 4.9±2.0 mmol.l-1.
Conclusion:
RPY may be described as a function of BLC. This may be useful in using BLC to explain the inter-individual variations in the relative utilisation of carbohydrate and fat during incremental exercise.
| Original language | English |
|---|---|
| Pages | 519 |
| Number of pages | 1 |
| Publication status | Published - Jul 2008 |
| Event | 13th Annual Congress of the European College of Sport Science (ECSS), 9-12 July, 2008, Lisbon, Portugal. - Estoril, Lisbon, Portugal Duration: 9 Jul 2008 → 12 Jul 2008 |
Conference
| Conference | 13th Annual Congress of the European College of Sport Science (ECSS), 9-12 July, 2008, Lisbon, Portugal. |
|---|---|
| Country/Territory | Portugal |
| City | Lisbon |
| Period | 9/07/08 → 12/07/08 |