In this study, the correlations between blood lactate concentration (BLC), different vector electrocardiogram (VECG) parameters, ventilatory parameters and heart rate during exercise and recovery periods were investigated. The aim was to clarify the relationships between VECG parameters and different exercise intensity markers. Six (25–37 years old) nonathlete, healthy, male participants took part in the study. All participants performed two different bicycle ergospirometric protocols (P1 and P2) in order to attain different lactate levels with different heart rate profiles. A principal component regression (PCR) approach is introduced for preprocessing the VECG components. PCR was compared to Sawitzcy Golay and wavelet filtering methods using simulated data. The performance of the PCR approach was clearly better in low signal-to-noise ratio (SNR) situations, and thus, it enables reliable VECG estimates even during intensive exercise. As a result, strong positive mean individual correlations between BLC and T-wave kurtosis (P1: r =0.86 and P2: r =0.8, p <0.05 in 12/12 measurements) and negative correlation between BLC and cosRT (P1: r =−0.7, P2: r =−0.62, p <0.05 in 8/12 measurements) were observed. The results of this study indicate that VECG parameters (in addition to heart rate) can make a significant contribution to monitoring of exercise intensity and recovery. 
The correlation of vectorcardiographic changes to blood lactate concentration during an exercise test