Acute High-Intensity Single-Leg Cycling Decreases Perceived Exertion Associated with Subsequent Submaximal Exercise

Abstract

Previous investigators have reported that nociceptive afferent neurons innervating skeletal muscles respond to a milieu of metabolic byproducts typical of high intensity exercise. Neural inhibitory responses may be reduced following benign exposure to stimuli. PURPOSE: The purpose of this investigation was to evaluate physiological and perceptual responses to an acute trial of high intensity single-leg cycling. We hypothesized that acute exposure to high concentrations of metabolic byproducts would habituate afferent nociceptors and ultimately reduce perceived exertion associated with subsequent exercise. METHODS: Five trained cyclists (age: 27±10 yrs) performed a graded cycling exercise test (3 min; 35 watt/stage) to determine power at lactate threshold (1 mmol above baseline) before (baseline) and 48hr after acute single-leg cycling. Blood lactate, heart rate (HR), oxygen consumption (VO2), and rating of perceived exertion (RPE) were assessed during the final 30s of each stage. Following the graded exercise test each participant performed single-leg cycling at 110% of their double-leg lactate threshold power (251±38 watts). Participants cycled repeatedly at this power until volitional failure. Trials were repeated until participants had accumulated a total of 5min. Legs were exercised with a counter balanced design. Differences in dependent variables were assessed using paired t-tests. RESULTS: Compared to baseline, RPE decreased (12.2 vs. 11.4; p< 0.01) and HR decreased (150 vs. 148; p=0.05), There were no alterations in blood lactate and VO2. Peak lactate concentrations following single-leg cycling trials were 13 ± 2.2 mmol/L. CONCLUSSION: These data demonstrate that an acute exposure to an extraordinarily high perturbation of the metabolic milieu reduced perceived exertion associated with subsequent sub maximal exercise. Note that blood lactates concentrations following single-leg cycling were similar to those associated with maximal aerobic exercise but were produced within the muscles of one leg. Thus, the disturbance in homeostasis in those muscles was likely twice as large. These results may have implications for treatment of patients with inappropriately functioning nocioceptors (e.g., fibromyalgia). Supported by PEAK Graduate Student Research Grant.