Unsteady physiology and perception during long “steady state” runs. What role do training characteristics play?

Abstract

PURPOSE: To contribute to a better understanding of low-intensity (<LT1) endurance training by quantifying and explaining the physiological mechanisms associated with cardiac drift and fatigue during low-intensity running and relate them to training characteristics. […] RESULTS: There was a significant drift for heart rate, oxygen consumption, ventilation, RER and RPE during both runs (P<0.05). There was no difference in drift between groups for any measurements, except for running economy during LR100. The drift was similar during LR90 and LR100 for all measurements except RER, which was significantly greater during LR90 (P<0.05). CONCLUSION: The present study demonstrates that an upward drift occurs for HR, RPE, ventilation, RER, and oxygen consumption for well-trained runners when running at an intensity corresponding to below or approximating LT1for 120 minutes. The study also demonstrates that while wide differences are seen at the individual level, there is no consistent difference in the magnitude of physiological or perceptual changes observed between two groups differing by XX% in weekly training volume. KEYWORDS: Endurance, running, low-intensity training, cardiac-drift, fatigue, electromyography