Measuring Chuckwagon Racehorse Movement Asymmetry Before and After Racing Using Wearable GNSS-IMUs: A Preliminary Study.

Objective Overview

• This study investigated the movement symmetry of Thoroughbred horses involved in Chuckwagon racing by measuring their gait asymmetry before and after races using wearable GNSS-IMU sensors.
• The research aimed to understand how racing affects locomotion symmetry and to explore possible links between asymmetry patterns and musculoskeletal injuries.

Background and Rationale

• Chuckwagon racing involves teams of four Thoroughbred horses pulling wagons at high speeds on a track.
• Movement symmetry during trot is an important indicator linked to how force is produced by the horse’s limbs, the direction the horse is racing in, and the presence of lameness or injury.
• Monitoring gait asymmetry can help in early detection of injuries and assessment of the horse’s biomechanical health.

Methodology

• The study was conducted over a 10-day period involving 60 Thoroughbred racehorses, averaging about 8 horses assessed per day.
• Each horse was equipped with wearable sensors combining Global Navigation Satellite Systems (GNSS) and Inertial Measurement Units (IMUs) to track precise movement metrics.
• Data were collected during on-track warmups (before racing) and cooldowns (after racing) to compare changes in locomotion symmetry.

Data Collection and Metrics

• Two key asymmetry metrics were used:
  • Minimum Difference (MnD): Quantifies weight-bearing asymmetry by measuring the difference in vertical trunk displacement between diagonal limb pairs during trot.
  • Upwards Difference (UpD): Measures push-off asymmetry, reflecting differences in how forcefully limbs push off during movement.
• Both metrics were expressed in absolute terms (millimeters) and normalized as a percentage of range of motion (% ROM) for better comparison.
• Linear mixed models were applied to compare asymmetries between warmups and cooldowns statistically.

Key Findings

• Weight-bearing asymmetry (MnD) was similar before and after racing:
  • Warmup: 6.2 mm (17.6%)
  • Cooldown: 6.4 mm (19.7%)
• Push-off asymmetry (UpD) increased significantly after racing:
  • Warmup: 11.3 mm (31.7%)
  • Cooldown: 12.8 mm (38.0%)
  • Statistical significance was p = 0.046, indicating a real increase in push-off asymmetry post-race.
• No other asymmetry differences displayed significant changes (p-values ≥ 0.202).
• One horse experienced a catastrophic musculoskeletal injury during the study:
  • This horse displayed high and variable UpD values during warmups (3.3–29.7 mm; 11.4–69.3%) and consistently high UpD values in cooldowns (24.3–25.5 mm; 47.8–76.4%).
• However, similar asymmetry magnitudes were also observed in uninjured horses, indicating high asymmetry alone does not definitively signal injury.

Interpretation and Implications

• The increase in push-off asymmetry after racing suggests that the physical strain of Chuckwagon racing affects how horses generate force with their limbs.
• High asymmetry levels may be indicative of stress or fatigue in the musculoskeletal system but are not sufficient alone to predict injury without additional data.
• The case of the injured horse highlights potential patterns that may precede injury, but more extensive research is necessary to confirm these associations.
• The study underscores the value of wearable GNSS-IMU technology in continuously monitoring racehorse biomechanics in real racing environments.

Future Directions

• Establishing baseline or normal ranges of movement asymmetry specific to Chuckwagon racing horses is critical for better interpretation of sensor data.
• Longitudinal studies tracking asymmetry patterns over time might help identify early warning signs for musculoskeletal injuries.
• Investigations could expand to assess asymmetry in different gaits or racing conditions and include larger cohorts for better statistical power.
• Integration with veterinary assessments and clinical outcomes will improve understanding of the relationship between measured asymmetries and health status.