La variabilidad de la frecuencia cardiaca en el control del entrenamiento en un corredor de Ironman: estudio de caso

The objective of this article is to provide information on the relationship between external (TL) and internal training load (ITL) from the tracking of an athlete during seven months of preparation for an Ironman competition (3.8 km of swimming, 180 km of cycling, and 42,195 km of running), using a training methodology with daily records of the heart rate variability (HRV). As a variable to assess parasympathetic activity, the square root of the mean of the differences in the sum of the squares between adjacent RR intervals (RMSSD) was calculated, together with the stress score (SS) as an indicator of sympathetic activity. In months two, three and four, there was a moderate increase in SS (d = 1.17) parallel to a moderate decrease in RMSSD (d = -1.04). In months five, six, and seven, a small decrease in SS (d = -0.23) and a moderate increase in RMSSD (d = 1.08) were observed. As a conclusion, the five-minute HRV measurements upon awakening appear to be a useful tool to monitor the state of parasympathetic equilibrium in a triathlete before approaching training sessions. The analysis of this monitoring would serve to detect possible fatigue states in the early stages and to modify, if necessary, the training load planning in preparation for an Ironman competition.