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Animals : an open access journal from MDPI2025; 15(16); 2449; doi: 10.3390/ani15162449

Exploring Monthly Variation of Gait Asymmetry During In-Hand Trot in Thoroughbred Racehorses in Race Training.

Abstract: Based on fundamental mechanics, movement and force associate head and pelvic movement asymmetry with asymmetry of force production. We investigate, how often racehorses undergoing strenuous training regimens show evidence of switching between "preferred" limbs, i.e. one limb producing increased force, when assessed at monthly intervals? We hypothesize that clinical asymmetry thresholds designed for "detecting lameness" are frequently exceeded and that when applying previously established Thoroughbred-specific repeatability values, horses rarely switch between showing left- and right-sided asymmetry. Monthly gait assessments (inertial sensors) were conducted in 256 Thoroughbred racehorses at least twice per horse (up to 16 times per horse). Descriptive statistics for absolute differences for head and pelvic movement were compared to published Thoroughbred-specific repeatability values. The percentage of left-right switches between repeat assessments was calculated in comparison to three different levels of pre-defined thresholds (perfect symmetry, clinical lameness thresholds, previously established Thoroughbred-specific repeatability values) and switch frequencies compared between the three thresholds. Ranges containing 95% of monthly differences were higher than published daily and weekly values except for pelvic vertical range of motion. Approximately 30% of monthly differences in individual symmetry parameters showed left-right switches around "perfect symmetry". Utilizing clinical lameness thresholds for categorizing left-right switches, a significantly ( < 0.001) reduced percentage of 4-11% of measurements for head movement and 7-17% for pelvic movement showed switches. Using daily repeatability values for categorization, a further significantly ( < 0.001) reduced percentage of switches was observed: 0.3-3.6% for head movement and 0.6-7.0% for pelvic movement. While racehorses in training regularly switch between small left- or right-sided movement symmetries, they less frequently switch between more pronounced left- and right-sided movement symmetries defined based on daily variations. Further studies should investigate the reasons for these rare switches.
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Publication Date: 2025-08-20 PubMed ID: 40867777PubMed Central: PMC12383056DOI: 10.3390/ani15162449Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This study examines how gait asymmetry, specifically left- or right-sided limb force preference, varies monthly in Thoroughbred racehorses during intense training.
  • It aims to assess how often horses switch their side of asymmetry and whether clinical thresholds for lameness are frequently exceeded over monthly intervals.

Background and Purpose

  • Gait asymmetry in horses is closely linked with differing force production between limbs and can be detected by measuring head and pelvic movements.
  • Asymmetries can reflect lameness or other biomechanical issues, thus monitoring these can help in early diagnosis or management of racehorses’ health.
  • This study investigates two main questions:
    • How frequently do Thoroughbred racehorses show monthly switches in limb force preference (left vs. right asymmetry)?
    • Do horses often exceed clinical thresholds designed for detecting lameness when assessed monthly?
  • Hypothesis: While clinical asymmetry thresholds are often exceeded, horses rarely switch sides (from left to right asymmetry or vice versa) when examined using breed-specific repeatability criteria.

Methodology

  • Population:
    • 256 Thoroughbred racehorses undergoing intense race training.
    • Each horse was assessed at least twice, with some assessed up to 16 times monthly.
  • Data collection:
    • Gait symmetry assessed using inertial sensor technology to measure head and pelvic movements during in-hand trot.
    • Parameters measured include absolute differences in vertical movement ranges of head and pelvis.
  • Analysis:
    • Results compared to published repeatability values specific to Thoroughbreds, which define natural variation thresholds.
    • Three thresholds used for defining asymmetry switches:
      • Perfect symmetry (zero difference)
      • Clinical lameness thresholds (previously established cut-offs to detect lameness)
      • Thoroughbred-specific repeatability values (daily variation-based thresholds)
    • Frequency of left-to-right or right-to-left switches calculated at monthly intervals for head and pelvic movement asymmetries.
    • Statistical tests used to assess significance of differences in switch frequencies between threshold levels (p < 0.001 significance reported).

Key Findings

  • Monthly variability:
    • The range including 95% of monthly differences was larger than daily or weekly variation, except for pelvic vertical motion range.
  • Switch frequency around perfect symmetry:
    • About 30% of monthly measurements switched sides at this fine-grained level, indicating regular small shifts between left and right bias.
  • Switch frequency using clinical lameness thresholds:
    • Lower switch rate observed: 4-11% for head movement and 7-17% for pelvic movement.
    • These thresholds filter out small fluctuations and highlight more clinically relevant asymmetry changes.
  • Switch frequency using breed-specific repeatability (daily variation) thresholds:
    • Switches became even rarer—0.3-3.6% for head and 0.6-7% for pelvic movement.
    • This reflects that significant side-to-side changes in asymmetry are relatively uncommon over monthly timescales.
  • Interpretation:
    • Racehorses frequently display small, transient asymmetry shifts between left and right limbs.
    • However, they rarely show pronounced switches beyond natural daily variation, suggesting true marked asymmetry changes are infrequent.

Implications and Future Directions

  • Monitoring of gait asymmetry should account for natural variation and measurement repeatability.
  • Frequent minor asymmetry fluctuations do not necessarily indicate clinical lameness.
  • The rare but more marked switches in asymmetry warrants further study to understand underlying causes, such as injury, fatigue, or biomechanical adaptations.
  • Improved longitudinal gait monitoring protocols could help trainers and veterinarians distinguish between normal gait variability and pathological gait changes in racehorses.

Cite This Article

APA
Pfau T, Forbes B, Sepulveda-Caviedes F, Chan Z, Weller R. (2025). Exploring Monthly Variation of Gait Asymmetry During In-Hand Trot in Thoroughbred Racehorses in Race Training. Animals (Basel), 15(16), 2449. https://doi.org/10.3390/ani15162449

Publication

Animals : an open access journal from MDPI
ISSN: 2076-2615
NlmUniqueID: 101635614
Country: Switzerland
Language: English
Volume: 15
Issue: 16
PII: 2449

Researcher Affiliations

Pfau, Thilo
  • Faculty of Kinesiology, University of Calgary, Calgary, AB T2N 1N4, Canada.
  • Faculty of Veterinary Medicine, University of Calgary, Calgary, AB T2N 1N4, Canada.
Forbes, Bronte
  • Hong Kong Jockey Club, Hong Kong, China.
Sepulveda-Caviedes, Fernanda
  • Department of Clinical Science and Services, The Royal Veterinary College, Hatfield AL9 7TA, UK.
Chan, Zoe
  • Faculty of Kinesiology, University of Calgary, Calgary, AB T2N 1N4, Canada.
Weller, Renate
  • Faculty of Veterinary Medicine, University of Calgary, Calgary, AB T2N 1N4, Canada.

Grant Funding

  • vet/prj/767 / Horserace Betting Levy Board

Conflict of Interest Statement

F.S.-C.’s postdoctoral study has been funded by the Horserace Betting Levy Board. The funder had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results. T.P. and R.W. are co-owners of EquiGait Ltd., a company offering gait analysis products and services. Bronte Forbes is an employee of the Hong Kong Jockey Club. The remaining author declares no conflicting interests.

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Citations

This article has been cited 1 times.
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