Experiment and computer-aided simulation: complementary tools to understand exercise metabolism

During the last two decades the concept of the MLSS (maximal lactate steady state) has been established. The MLSS detects the highest level of the BLC (blood lactate concentration) and the corresponding workload (MLSS workload) that can be maintained over time without continual BLC accumulation. In spite of a lack of experimental and/or theoretical foundation, it has been speculated that the level of the MLSS may decrease with increasing performance capacity. The potential inter-relationship between performance capacity and BLC response to prolonged constant workload will be analysed based on a recent study, which provided evidence that the MLSS is independent of performance whereas MLSS workload increases with performance capacity, and by a computer-aided simulation. The simulated model modifies and combines previous theories put forward to explain the response of BLC to exercise and incorporates a theory about limiting factors of oxygen transport to the muscle cell. Simulations consider the BLC response to selected prolonged constant workloads while paying special respect to changes in body structure and substrate utilization, which are generally accepted as limiting factors of performance capacity. This complex modulation of appearance and disappearance of lactate during constant prolonged exercise seems to support the experimental results, which indicated independence between MLSS and performance capacity.