Correlation of detrended fluctuation analysis alpha 1 with blood lactate concentration in field standardised exercise tests in sport horses

Abstract

Methods to determine exercise intensity thresholds, such as the aerobic and anaerobic threshold, that separate different exercise intensities in exercising horses in the field setting or on the treadmill often require equipment, standardised conditions and/or blood sampling. Detrended fluctuation analysis (DFA) is a heart rate variability variable proposed as a non-invasive tool for exercise intensity monitoring and with a potential association with exercise intensity thresholds and fatigue. The objectives of this study were to (1) describe the first component of DFA (DFA-α1) during standardised field incremental exercise tests in sport horses in active Eventing competition and in sport horses ridden without the goal of participating in competitions, and (2) to determine if DFA-α1 is associated with blood lactate concentration. Null hypotheses of the study were that (1) DFA-α1 is not correlated with blood lactate concentration measurements and (2) the correlation between DFA-α1 and blood lactate concentration is not stronger than the one between blood lactate concentration and heart rate or blood lactate concentration and speed. An in vivo observational study was performed analysing exercising electrocardiograms obtained in 59 standardised exercise tests in the field. DFA-α1 was significantly and moderately correlated with blood lactate concentration (, ). A strong correlation was observed between blood lactate concentration and speed (, ), as well as between blood lactate concentration and heart rate (, ). DFA-α1 correlation with blood lactate concentration was moderate but weaker than the correlation of blood lactate concentration and heart rate or blood lactate concentration and speed. DFA-α1 was not a useful surrogate of blood lactate concentration in field incremental standardised tests used for sport horses in this setting.