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Cardiac Cost During Submaximal Exercise as a Practical Monitoring Tool in French Standardbred Trotters: Short-Term Reproducibility of Non-Invasive Field-Derived Indicators
1
Movement, Balance, Performance, and Health Laboratory (EA 4445), Université de Pau et des Pays de l’Adour, 65000 Tarbes, France
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Horse Run Impulse Association, 77123 Noisy-sur-Ecole, France
3
Faculty of Sport Science, Université Évry Paris-Saclay, 91000 Évry-Courcouronnes, France
*
Author to whom correspondence should be addressed.
Animals 2026, 16(11), 1598; https://doi.org/10.3390/ani16111598 (registering DOI)
Submission received: 21 April 2026
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Revised: 19 May 2026
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Accepted: 21 May 2026
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Published: 24 May 2026
(This article belongs to the Section Equids)
Simple Summary
Monitoring how racehorses respond to exercise is important for adjusting training and detecting poor adaptation early. However, repeated measurements are only useful if they remain stable enough from one session to the next. This study examined which heart-related and speed-related indicators could be used for short-term monitoring in French Standardbred trotters during standardized training sessions. Each session included a warm-up followed by two exercise bouts at increasing intensity, while heart rate and speed were recorded with a wearable monitoring system. Data were collected from 483 sessions in 60 horses. Short-term repeatability was assessed in a subset of 126 sessions in 18 horses, selected by grouping repeated monitored sessions from the same horse when they were no more than 7 days apart. The most repeatable indicators were cardiac cost during the first exercise bout, heart rate measured 60 s after exercise, and the speed reached when heart rate first exceeded 150 beats per minute. By contrast, some other indicators, especially those derived from higher exercise intensities, were less stable from one session to the next. These results suggest that simple non-invasive measures recorded during routine training may help trainers and drivers monitor horses more effectively in the short term. The findings should nevertheless be interpreted with caution, because the study was based on horses from a single training yard.
Abstract
Routine monitoring in racehorses requires indicators that are reproducible and practical under real training conditions. This observational study evaluated the short-term reproducibility of cardiovascular and speed indicators in French Standardbred trotters, with a particular focus on cardiac cost (CC), defined as the ratio of heart rate to speed (beats·m−1). The full dataset comprised 483 sessions from 60 trotters and was used to describe age-related patterns. For reproducibility analyses, consecutive monitored sessions within the same horse were grouped into follow-up blocks when the interval between two successive sessions did not exceed 7 days. Only follow-up blocks containing at least three sessions were retained, resulting in 36 blocks, 126 sessions, and 18 horses. Each session included a warm-up, two 2000 m work blocks at increasing intensity, and recovery periods, while heart rate and speed were recorded using a Polar Team Pro system. Adjusted intraclass correlation coefficients indicated moderate reproducibility for CC during the first work block (CC B1: 0.67, 95% CI 0.48–0.78), heart rate recovery (HRR) after B1 (0.60, 0.40–0.73) and B2 (0.66, 0.47–0.78), and V150 (0.59, 0.39–0.73), whereas V180, recovery speed, and CC during B2 showed poor reproducibility. Reproducibility of CC B1 and HRR was preserved after adjustment for ambient temperature. In the full dataset, V200 increased with age, consistent with previous field-test literature. The minimal detectable change was 0.04 beats·m−1 for CC B1 and 26 bpm for HRR after B1. These findings suggest that CC B1, HRR, and V150 may be useful indicators for short-term monitoring, although results should be interpreted considering the single-yard design.
