Assessment of Metabolic Flexibility by Means of Measuring Blood Lactate, Fat, and Carbohydrate Oxidation Responses to Exercise in Professional Endurance Athletes and Less-Fit Individuals
- 1.2k Downloads
Increased muscle mitochondrial mass is characteristic of elite professional endurance athletes (PAs), whereas increased blood lactate levels (lactatemia) at the same absolute submaximal exercise intensities and decreased mitochondrial oxidative capacity are characteristics of individuals with low aerobic power. In contrast to PAs, patients with metabolic syndrome (MtS) are characterized by a decreased capacity to oxidize lipids and by early transition from fat to carbohydrate oxidation (FATox/CHOox), as well as elevated blood lactate concentration [La−] as exercise power output (PO) increases, a condition termed ‘metabolic inflexibility’.
The aim of this study was to assess metabolic flexibility across populations with different metabolic characteristics.
We used indirect calorimetry and [La−] measurements to study the metabolic responses to exercise in PAs, moderately active individuals (MAs), and MtS individuals.
FATox was significantly higher in PAs than MAs and patients with MtS (p < 0.01), while [La−] was significantly lower in PAs compared with MAs and patients with MtS. FATox and [La−] were inversely correlated in all three groups (PA: r = −0.97, p < 0.01; MA: r = −0.98, p < 0.01; MtS: r = −0.92, p < 0.01). The correlation between FATox and [La−] for all data points corresponding to all populations studied was r = −0.76 (p < 0.01).
Blood lactate accumulation is negatively correlated with FATox and positively correlated with CHOox during exercise across populations with widely ranging metabolic capabilities. Because both lactate and fatty acids are mitochondrial substrates, we believe that measurements of [La−] and FATox rate during exercise provide an indirect method to assess metabolic flexibility and oxidative capacity across individuals of widely different metabolic capabilities.
Compliance with Ethical Standards
Conflict of interest
Iñigo San-Millán and George A. Brooks declare that they have no conflicts of interest that are directly relevant to the content of this article.
The authors declare that no financial support was received for the conduct of this study or the preparation of this article.
- 5.Bergman BC, Butterfield GE, Wolfel EE, Casazza GA, Lopaschuk GD, Brooks GA. Evaluation of exercise and training on muscle lipid metabolism. Am J Appl Physiol. 1999;276:E106–17.Google Scholar
- 6.Bergman BC, Butterfield GE, Wolfel EE, Lopaschuk GD, Casazza GA, Horning MA, et al. Muscle net glucose uptake and glucose kinetics after endurance training in men. Am J Appl Physiol. 1999;277:E81–92.Google Scholar
- 24.Blaak EE, Wagenmakers A, Glatz J. Plasma free fatty acid utilisation and fatty acid binding protein content are diminished in forearm skeletal muscle of type 2 diabetic subjects. Am J Physiol. 2000;279:E146–54.Google Scholar
- 51.Turcotte LP, Richter EA, Kiens B. Increased plasma FFA uptake and oxidation during prolonged exercise in trained vs. untrained humans. Am J Physiol. 1992;262:791–9.Google Scholar
- 56.Donovan CM, Brooks GA. Endurance training affects lactate clearance, not lactate production. Am J Physiol. 1983;244:83–92.Google Scholar