Comparative kinematic analysis of the leading and trailing forelimbs of horses cantering on a turf and a synthetic surface

Evaluation of surface type and time of day on agility course performance

Introduction

Canine agility competitions are performed on a variety of surfaces. In the equine and human literature, surface type has been associated with speed, performance, and injury risk. The aim of this study was to evaluate the effect of general surface type and time of day on calculated speed (yards per second over a measured course distance) and course performance during the UKI Agility International (UKI) U.S. Open. We hypothesized that surface type would affect calculated speed, with sand being the slowest.

Materials and methods

Data on course performance from the 2021 and 2022 events were obtained directly from UKI. The officiating judge measured course length, automatic timers recorded dogs' course times, and speeds were calculated from these values. Three surfaces (dirt, grass, and sand) were compared across three categories of courses (jumpers, standard, and speedstakes). Differences in calculated speeds and qualifying rates were estimated using generalized estimating equations (GEE) to account for multiple runs by the same handler.

Results

Among jumpers courses, those run on sand in 2021 were markedly slower than those run on dirt. Grass and dirt were more similar in terms of average calculated speed, though some courses run on grass were significantly faster than courses run on dirt and vice versa. Time of day effects observed were inconsistent, with more variability observed for dirt and sand than for grass.

Discussion

There was a notable variation in calculate speed based on surface with sand being slowest, likely due to the increased energy cost required to run on sand due to its high compliance. Calculated speeds on grass and dirt appeared generally similar, but there was substantial variability of calculated speed among various courses, making comparison of surface effects challenging. Variables within the surface itself (such as compaction level and moisture content) likely play a role in the effects of surface on speed and performance. This study provides insight into the complexity of surface effects on performance in agility dogs and highlights the need for canine-specific surface studies on the effect of surface variables and how these relate to risk of development of musculoskeletal injuries.

Changes in muscle activation with graded surfaces during canter in Thoroughbred horses on a treadmill

Understanding how muscle activity changes with different surface grades during canter is essential for developing training protocols in Thoroughbreds because canter is their primary gait in training and races. We measured the spatiotemporal parameters and the activation of 12 surface muscles in the leading limb side of 7 Thoroughbreds. Horses were equipped with hoof strain gauges and cantered at 10 m/s on a treadmill set to grades of -4%, 0%, 4%, and 8%, randomly, for 30 seconds each without a lead change. Integrated electromyography (iEMG) values during stance and swing phases were calculated and normalized to mean iEMG values during stride duration at 0% grade in each muscle. The iEMG values at each grade were compared using a generalized mixed model. Stride duration significantly decreased due to shorter swing duration on an 8% grade (P < 0.001) compared to all other grades, where no significant changes were observed. Compared to a 0% grade, the normalized iEMG values during the stance phase on an 8% grade in five muscles significantly increased (Musculus infraspinatus; +9%, M. longissimus dorsi (LD); +4%, M. gluteus medius (GM); +29%, M. biceps femoris; +47%, M. flexor digitorum lateralis; +16%). During the swing phase, the normalized iEMG values in six muscles significantly increased on an 8% grade compared to a 0% grade (M. splenius; +21%, M. triceps brachii; +54%, LD; +37%, GM; +24%, M. semitendinosus; +51%, M. extensor digitorum longus; +10%). No significant changes were observed in iEMG values on -4% and 4% grades compared to the 0% grade. Although +/- 4% grades had little effect on neuromuscular responses, 8% uphill canter reduced stride duration due to decreased swing duration and required increase of muscle activation during either stance and swing phase. Canter on an 8% grade might strengthen equine muscles to increase propulsive force and stride frequency.

Timing Differences in Stride Cycle Phases in Retired Racehorses Ridden in Rising and Two-Point Seat Positions at Trot on Turf, Artificial and Tarmac Surfaces

Injuries to racehorses and their jockeys are not limited to the racetrack and high-speed work. To optimise racehorse-jockey dyads' health, well-being, and safety, it is important to understand their kinematics under the various exercise conditions they are exposed to. This includes trot work on roads, turf and artificial surfaces when accessing gallop tracks and warming up. This study quantified the forelimb hoof kinematics of racehorses trotting over tarmac, turf and artificial surfaces as their jockey adopted rising and two-point seat positions. A convenience sample of six horses was recruited from the British Racing School, Newmarket, and the horses were all ridden by the same jockey. Inertial measurement units (HoofBeat) were secured to the forelimb hooves of the horses and enabled landing, mid-stance, breakover, swing and stride durations, plus stride length, to be quantified via an in-built algorithm. Data were collected at a frequency of 1140 Hz. Linear Mixed Models were used to test for significant differences in the timing of these stride phases and stride length amongst the different surface and jockey positions. Speed was included as a covariate. Significance was set at p < 0.05. Hoof landing and mid-stance durations were negatively correlated, with approximately a 0.5 ms decrease in mid-stance duration for every 1 ms increase in landing duration (r2 = 0.5, p < 0.001). Hoof landing duration was significantly affected by surface (p < 0.001) and an interaction between jockey position and surface (p = 0.035). Landing duration was approximately 4.4 times shorter on tarmac compared to grass and artificial surfaces. Mid-stance duration was significantly affected by jockey position (p < 0.001) and surface (p = 0.001), speed (p < 0.001) and jockey position*speed (p < 0.001). Mean values for mid-stance increased by 13 ms with the jockey in the two-point seat position, and mid-stance was 19 ms longer on the tarmac than on the artificial surface. There was no significant difference in the breakover duration amongst surfaces or jockey positions (p ≥ 0.076) for the ridden dataset. However, the mean breakover duration on tarmac in the presence of a rider decreased by 21 ms compared to the in-hand dataset. Swing was significantly affected by surface (p = 0.039) and speed (p = 0.001), with a mean swing phase 20 ms longer on turf than on the artificial surface. Total stride duration was affected by surface only (p = 0.011). Tarmac was associated with a mean stride time that was significantly reduced, by 49 ms, compared to the turf, and this effect may be related to the shorter landing times on turf. Mean stride length was 14 cm shorter on tarmac than on grass, and stride length showed a strong positive correlation with speed, with a 71 cm increase in stride length for every 1 m s-1 increase in speed (r2 = 0.8, p < 0.001). In summary, this study demonstrated that the durations of the different stride cycle phases and stride length can be sensitive to surface type and jockey riding position. Further work is required to establish links between altered stride time variables and the risk of musculoskeletal injury.

Hipparion tracks and horses' toes: the evolution of the equid single hoof

The traditional story of the evolution of the horse (family Equidae) has been in large part about the evolution of their feet. How did modern horses come to have a single toe (digit III), with the hoof bearing a characteristic V-shaped keratinous frog on the sole, and what happened to the other digits? While it has long been known that the proximal portions of digits II and IV are retained as the splint bones, a recent hypothesis suggested that the distal portion of these digits have also been retained as part of the frog, drawing upon the famous Laetoli footprints of the tridactyl (three-toed) equid Hipparion as part of the evidence. We show here that, while there is good anatomical and embryological evidence for the proximal portions of all the accessory digits (i.e. I and V, as well as II and IV) being retained in the feet of modern horses, evidence is lacking for the retention of any distal portions of these digits. There is also good ichnological evidence that many tridactyl equids possessed a frog, and that the frog has been part of the equid foot for much of equid evolutionary history.

Electromyographic and Kinematic Comparison of the Leading and Trailing Fore- and Hindlimbs of Horses during Canter

This study compared muscle activity and movement between the leading (Ld) and trailing (Tr) fore- (F) and hindlimbs (H) of horses cantering overground. Three-dimensional kinematic and surface electromyography (sEMG) data were collected from right triceps brachii, biceps femoris, middle gluteal, and splenius from 10 ridden horses during straight left- and right-lead canter. Statistical parametric mapping evaluated between-limb (LdF vs. TrF, LdH vs. TrH) differences in time- and amplitude-normalized sEMG and joint angle-time waveforms over the stride. Linear mixed models evaluated between-limb differences in discrete sEMG activation timings, average rectified values (ARV), and spatio-temporal kinematics. Significantly greater gluteal ARV and activity duration facilitated greater limb retraction, hip extension, and stifle flexion (p < 0.05) in the TrH during stance. Earlier splenius activation during the LdF movement cycle (p < 0.05), reflected bilateral activation during TrF/LdH diagonal stance, contributing to body pitching mechanisms in canter. Limb muscles were generally quiescent during swing, where significantly greater LdF/H protraction was observed through greater elbow and hip flexion (p < 0.05), respectively. Alterations in muscle activation facilitate different timing and movement cycles of the leading and trailing limbs, which justifies equal training on both canter leads to develop symmetry in muscular strength, enhance athletic performance, and mitigate overuse injury risks.

Neurological scoring and gait kinematics to assess functional outcome in an ovine model of ischaemic stroke

Background

Assessment of functional impairment following ischaemic stroke is essential to determine outcome and efficacy of intervention in both clinical patients and pre-clinical models. Although paradigms are well described for rodents, comparable methods for large animals, such as sheep, remain limited. This study aimed to develop methods to assess function in an ovine model of ischaemic stroke using composite neurological scoring and gait kinematics from motion capture.

Methods

Merino sheep (n = 26) were anaesthetised and subjected to 2 hours middle cerebral artery occlusion. Animals underwent functional assessment at baseline (8-, 5-, and 1-day pre-stroke), and 3 days post-stroke. Neurological scoring was carried out to determine changes in neurological status. Ten infrared cameras measured the trajectories of 42 retro-reflective markers for calculation of gait kinematics. Magnetic resonance imaging (MRI) was performed at 3 days post-stroke to determine infarct volume. Intraclass Correlation Coefficients (ICC's) were used to assess the repeatability of neurological scoring and gait kinematics across baseline trials. The average of all baselines was used to compare changes in neurological scoring and kinematics at 3 days post-stroke. A principal component analysis (PCA) was performed to determine the relationship between neurological score, gait kinematics, and infarct volume post-stroke.

Results

Neurological scoring was moderately repeatable across baseline trials (ICC > 0.50) and detected marked impairment post-stroke (p < 0.05). Baseline gait measures showed moderate to good repeatability for the majority of assessed variables (ICC > 0.50). Following stroke, kinematic measures indicative of stroke deficit were detected including an increase in stance and stride duration (p < 0.05). MRI demonstrated infarction involving the cortex and/or thalamus (median 2.7 cm³, IQR 1.4 to 11.9). PCA produced two components, although association between variables was inconclusive.

Conclusion

This study developed repeatable methods to assess function in sheep using composite scoring and gait kinematics, allowing for the evaluation of deficit 3 days post-stroke. Despite utility of each method independently, there was poor association observed between gait kinematics, composite scoring, and infarct volume on PCA. This suggests that each of these measures has discreet utility for the assessment of stroke deficit, and that multimodal approaches are necessary to comprehensively characterise functional impairment.

Investigation of Factors Influencing Thoroughbred Horses' Racing Career Length in Turkey

The aim of this research was to determine the average length of a Thoroughbred horse's racing career in Turkey using survival functions of Thoroughbred horses with various characteristics. In addition, the aim was to identify risk factors that could influence the duration of a Thoroughbred horse's racing career and develop a survival model that took these factors into account. A total of 11,721 Thoroughbred horses born in 2007 and later were included in the study population. The horses involved in the study were followed for a minimum of 1 year. Kaplan-Meier analysis was used to calculate the average length of racing career for each factor studied. Extended Cox regression analysis was used to determine the risk factors upon time of career ending and to create a survival model. Results showed that, the mean career length of Thoroughbred horses was 17.79 months (95% CI: 17.41-18.13). Also, "starting age of the race," "number of starts," "type of track where the race started," "racing on a single type racetrack" and "earning status" were found risk factors that affect the length of the racing career. Earnings was the top relative contributor to the established model, and its sole adjusted effect showed that being in the lowest earning group increased the hazard of career ending 2.28 times (95% CI:1.98-2.61) compared to horses with highest earning group. In conclusion, clear differences upon the length of racing career was observed for each investigated factor. Future studies should be considerate of these differences when analyzing population data.

Risk Factors for Jockey Falls in Japanese Thoroughbred Flat Racing

Jockey safety is of paramount importance from welfare perspective and public perception. This retrospective case-control study aims to identify risk factors associated with jockey falls (JF) in flat races of Japan Racing Association (JRA). JF in 715,210 race starts by 74,328 horses at 10 racecourses from 2003 to 2017 were reviewed. Data were extracted from a database maintained by JRA and from official accident reports issued by race stewards. Seventeen possible risk factors were evaluated using multivariable logistic regression, to identify those significantly associated with JF. A total of 992 JF incidents were recorded, with an incidence rate of 1.39 falls per 1,000 starts (95% CI: 1.30-1.48). 6 risk factors were significantly associated with JF. Odds increased with horses that sustained catastrophic musculoskeletal injury (CMI) (OR: 203; CI: 169-241; P < 0.001). Increased odds were also associated with dirt track surfaces (OR: 1.99; CI: 1.74-2.29; P < 0.001), apprentice jockeys (OR: 1.43; CI: 1.21-1.68; P < 0.001), smaller track sizes (OR: 1.41; CI: 1.24-1.61; P < 0.001), larger fields (OR: 1.25; CI: 1.07-1.47; P = 0.005), and longer race distances (OR per 200 m: 1.05; CI: 1.01-1.09; P = 0.02). Since CMI was identified as a major contributing factor for JF, measures to minimize CMI may lead to improvement of jockey safety. The increased odds associated with apprentice jockeys may indicate the importance of jockey education and training. For jockey safety, proper staffing of medical professionals especially for races on dirt, smaller track, larger fields, and longer distances is recommended.

Effects of sand, asphalt and 3-degree hind toe or heel elevation on horse kinematics

BACKGROUND

Although the effects of both the surfaces and plantar angles on equine locomotion have been widely discussed, limited scientific data are available.

METHODS

Our objectives were to determine the effects of two surfaces (asphalt and sand) and of 3-degree hind toe or heel elevation on horse kinematics in an experimental study. Six saddle horses were shod with a reference shoeing (REF), characterized by a fore aluminium (REF F) and hind steel racehorse (REF H) shoeing. Two dimensional kinematic videos compared horse's kinematic parameters when walking and trotting on asphalt and sand. On asphalt, REF was also compared with REF F and a modified REF H with additional 3-degree hind-toe or -heel wedges.

RESULTS

On asphalt versus sand, horses had, at the trot, a shorter stride duration and forelimb maximal retraction, and at walk and trot, a greater fetlock, carpus, elbow and tarsus extension, a greater fore and hind limbs maximal protraction and a shorter hind limbs maximal retraction. Increasing the plantar angle decreased the tarsus and hind fetlock extension, in contrast to fore-limb, on asphalt during the stance phase.

CONCLUSIONS

These findings could be useful to adapt rehabilitation programs related to fore and hind limb pathologies, at slow gaits.

The Protraction and Retraction Angles of Horse Limbs: An Estimation during Trotting Using Inertial Sensors

The protraction and retraction angles of horse limbs are important in the analysis of horse locomotion. This study explored two methods from an IMU positioned on the canon bone of eight horses to estimate these angles. Each method was based on a hypothesis in order to define the moment corresponding with the verticality of the canon bone: (i) the canon bone is in a vertical position at 50% of the stance phase or (ii) the verticality of the canon bone corresponds with the moment when the horse’s withers reach their lowest point. The measurements were carried out on a treadmill at a trot and compared with a standard gold method based on motion capture. For the measurement of the maximum protraction and retraction angles, method (i) had average biases (0.7° and 1.7°) less than method (ii) (−1.3° and 3.7°). For the measurement of the protraction and retraction angles during the stance phase, method (i) had average biases (4.1° and −3.3°) higher to method (ii) (2.1° and −1.3°). This study investigated the pros and cons of a generic method (i) vs. a specific method (ii) to determine the protraction and retraction angles of horse limbs by a single IMU.

Development of An Anybody Musculoskeletal Model of The Thoroughbred Forelimb

Musculoskeletal injuries in horses are the main cause of retirement, rest, and death. To understand these injuries, it is necessary to study loads in muscles, tendons and ligaments. A musculoskeletal model makes it possible to consider all structures simultaneously and avoids invasive measurements. At present, most computational models of the equine limb described in the literature have been limited to the distal limb. The aim of this study was to create a preliminary musculoskeletal model of the whole equine forelimb and to run it with kinematic data collected during gait. The model was developed with the AnyBody Modelling System. It includes six limb segments, 11 muscle groups and 17 ligaments. Kinematic data were collected from the right forelimb of four Thoroughbreds at trot, right and left lead canter, and were then used in the model to compute sagittal plane joint excursions and ligament and tendon strains. The modelled joint excursions were in reasonable agreement with previous reports in the literature despite breed, gait and surface differences. Strain patterns of the tendons of the suspensory apparatus agreed with the literature, with maxima in mid-stance or at the end of stance. Strains in the distal palmar ligaments peaked in mid-stance, while strain in lacertus fibrosus peaked at the stance-swing transition. Tendon and ligament strains at canter were greatest when the measured forelimb was the trailing limb. Strain amplitudes varied against earlier models and these differences are discussed in relation to variations in methods, and especially in relation to attachment points of tendons and ligaments.

Comparison of Trotting Stance Detection Methods from an Inertial Measurement Unit Mounted on the Horse's Limb

The development of on-board sensors, such as inertial measurement units (IMU), has made it possible to develop new methods for analyzing horse locomotion to detect lameness. The detection of spatiotemporal events is one of the keystones in the analysis of horse locomotion. This study assesses the performance of four methods for detecting Foot on and Foot off events. They were developed from an IMU positioned on the canon bone of eight horses during trotting recording on a treadmill and compared to a standard gold method based on motion capture. These methods are based on accelerometer and gyroscope data and use either thresholding or wavelets to detect stride events. The two methods developed from gyroscopic data showed more precision than those developed from accelerometric data with a bias less than 0.6% of stride duration for Foot on and 0.1% of stride duration for Foot off. The gyroscope is less impacted by the different patterns of strides, specific to each horse. To conclude, methods using the gyroscope present the potential of further developments to investigate the effects of different gait paces and ground types in the analysis of horse locomotion.