The dynamics of speed selection and psycho-physiological load during a mountain ultramarathon

Abstract

Background Exercise intensity during ultramarathons (UM) is expected to be regulated as a result of the development of psycho-physiological strain and in anticipation of perceived difficulties (duration, topography). The aim of this study was to investigate the dynamics of speed, heart rate and perceived exertion during a long trail UM in a mountainous setting. Methods Fifteen participants were recruited from competitors in a 106 km trail mountain UM with a total elevation gain and loss of 5870 m. Speed and gradient, heart rate (HR) and ratings of perceived exertion (dissociated between the general [RPEGEN] and knee extensor fatigue [RPEKE] and collected using a voice recorder) were measured during the UM. Self-selected speed at three gradients (level, negative, positive), HR, RPEGEN and RPEKE were determined for each 10% section of total event duration (TED). Results The participants completed the event in 18.3 ± 3.0 h, for a total calculated distance of 105.6 ± 1.8 km. Speed at all gradients decreased, and HR at all gradients significantly decreased from 10%to 70%, 80%and 90%, but not 100%of TED. RPEGEN and RPEKE increased throughout the event. Speed increased from 90%to 100%of TED at all gradients. Average speed was significantly correlated with total time stopped (r = -.772; p = .001; 95%confidence interval [CI] = -1.15, -0.39) and the magnitude of speed loss (r = .540; p = .038; 95%CI = -1.04, -0.03), but not with the variability of speed (r = -.475; p = .073; 95%CI = -1.00, 0.05). Conclusions Participants in a mountain UM event combined positive pacing strategies (speed decreased until 70-90% of TED), an increased speed in the last 10% of the event, a decrease in HR at 70-90% of TED, and an increase in RPEGEN and RPEKE in the last 30% of the event. A greater speed loss and less total time stopped were the factors associated with increased total performance. These results could be explained by theoretical perspectives of a complex regulatory system modulating motor drive in anticipation of perceived difficulties such as elevation changes.