Metabollc and cardiovascular response during the half Ironman triathlon. implication for performance

Abstract

The aims of this work were: 1) to determine the correlation between the Anaerobic Threshold (AT) and the performance on the triathlon of Half lronman; 2) to describe and to compare the Heart Rate (HR) and the correspondent speed at AT in swimming. cycling and running. with the HR and the speed of these events during the triathlon; 3) to describe the behavior of the lactate (LAC) and glucemia (GLU) during the events. Six males triathletes between the ages of 18 to 24 participated in this study. AT was defined as the speed corresponding to a lactate concentration of 4 mM and was determined by measuring plasma lactate concentration after each bout of swimming (3x200 m progressive), cycling (3x2400 m progressive) and running (3x1200 m progressive) tests. The speed at 4 mM lactate concentration was calculated by linear interpolation. The data were obtained during a Half Ironman (1.9 km swimming, 90 km cycling and 21 km running) competition. HR, LAC and GLU were determinated during the transition of the events and the end of the competition. HR was also determinated in three others points of control in the cycling and running course. Swimming and cycli1'!g AT were significantly correlated with the competition speed in these events (r = 0.92 and r = 0.92, respectively). However, the same did not occur in the running (r = 0.63). The swimming event speed (64.8 m/min) was not different from the speed at AT (65.5 m/min). On the other hand. the speed of cycling (538.0 m/min) and running (201.0 m/min) were significantly lower than the speed at AT (639.0 and 264.0 m/min respectively). The HR at swimming was higher (p > 0.05) than HR of AT. At running, only HR in the last two parts of the event, was significantly lower than HR of AT. During cycling , there were not significant differences between HR of the event and HR of AT. as well as HR among the four parts of the competition. The concentration of LAC in swimming was higher than cycling and running, but in these last two events there were no differences. GLU was lower just after the running, when compared to the figure obtained after swimming. These results suggest that: 1) AT is able to predict the performance of swimming and cycling during the triathlon competition of Half Ironman, but the same does not occur at running; 2) The use of HR to control the competition intensity. mainly during cycling and running, might present limitations.