Association of heart rate variability, exercise intensity and exercising arrhythmias with competition results in eventing horses

BACKGROUND

Exercising arrhythmias are common in horses participating in eventing competitions. Heart rate variability (HRV) and a specific measure of the degree of heart rate fluctuation (Detrended Fluctuation Analysis alpha1; DFA-α1) are proposed as exercise intensity and fatigue markers.

OBJECTIVES

(1) To describe exercising arrhythmias and DFA-α1 values during 2-4* level eventing cross-country competitions in horses from two European countries; (2) to identify associations between exercising arrhythmias, DFA-α1 and competition results and (3) to evaluate whether markers of the intensity of exercise are associated with exercising arrhythmias, DFA-α1 or competition results.

METHODS

A convenience sample of exercising ECGs and competition results from horses during cross-country eventing competitions was examined. Statistical analysis was conducted using multivariable mixed-effects logistic, Poisson and linear regression models.

RESULTS

Arrhythmias were frequent during 69 cross-country competition ECGs from 43 horses. Detrended fluctuation analysis α1 was not associated with performance during cross-country, but a higher DFA-α1 during cross-country was associated with fewer showjumping phase penalties. More premature complexes, the presence of complex arrhythmias and arrhythmias during recovery were associated with fewer time penalties during cross-country. The presence of complex arrhythmias and arrhythmias during recovery of the cross-country phase was associated with more penalties during the showjumping phase. Higher blood lactate concentration, higher HRpeak and higher HRmean were associated with fewer time penalties during cross-country.

MAIN LIMITATIONS

The arrhythmias observed do not allow conclusions to be drawn about the consequences of more severe arrhythmias. The associations described here were often of small magnitude or with large confidence intervals and must be interpreted cautiously.

CONCLUSIONS

Arrhythmias during the cross-country test of eventing competitions were frequently associated with positive competition results during the cross-country phase and negative results during the showjumping phase. The specific arrhythmia types and circumstances that should raise concern about performance and safety remain relevant but unanswered questions for equine practitioners.

Uniform Homeostatic Stress Through Individualized Interval Training Facilitates Homogeneous Adaptations Across Rowers With Different Profiles

PURPOSE

This study compared the effects of individualizing supramaximal interval rowing interventions using anaerobic power reserve (APR [high-intensity interval training (HIIT) prescribed according to individual APR (HIITAPR)]) and power associated with maximal oxygen uptake (WV˙O2max [HIIT prescribed based on the individual WV˙O2max (HIITW)]) on the homogeneity of physiological and performance adaptations.

METHODS

Twenty-four well-trained rowers (age 24.8 [4.3] y, stature 182.5 [3] cm, body mass 86.1 [4.3]) were randomized into interventions consisting of 4 × 30-second intervals at 130%APR (WV˙O2max + 0.3 × maximal sprint power) with weekly progression by increasing the number of repetitions per set (5, 6, 7, 8, 9, and 10, from first to sixth session) and the same sets and repetitions with the intensity described as 130% WV˙O2max. The work-to-recovery ratio was 1:1 for repetitions and 3 minutes between sets. Responses of aerobic fitness indices, power output, cardiac hemodynamics, locomotor abilities, and time-trial performance were examined.

RESULTS

Both HIITAPR and HIITW interventions significantly improved V˙O2max, lactate threshold, cardiac hemodynamics, and 2000-m performance, with no between-groups difference in changes over time. However, HIITAPR resulted in a lower interindividual variability in adaptations in V˙O2max and related physiological parameters, but this is not the case for athletic performance, which can depend on a multitude of factors beyond physiological parameters.

CONCLUSIONS

Results demonstrated that expressing supramaximal interval intensity as a proportion of APR facilitates imposing the same degrees of homeostatic stress and leads to more homogeneous physiological adaptations in maximal variables when compared to prescribing a supramaximal HIIT intervention using WV˙O2max. However, lower interindividual variability would be seen in submaximal variables if HIIT interventions were prescribed using WV˙O2max.