Kinematic analysis of the metacarpophalangeal joint during jump reception in Brasileiro de Hipismo breed horsesABSTRACT
The jumping kinematics vary among horse breeds, influencing their performance and athletic capability. The objective was to evaluate variations in the metacarpophalangeal joint angle during jump reception at different heights and widths through kinematic analysis. Fourteen Brasileiro de Hipismo (BH) horses were assessed using reflective markers. Vertical jumps of 90 and 120cm in height (V 90 and V 120) and oxer-type jumps with heights of 90 and 120cm (Ox 90 and Ox 120), with a width of 100 cm, were examined. Evaluations of the metacarpophalangeal joint angles occurred at two moments during jump reception (MT1) and (MT2) when the joint reached maximum hyperextension. Significant differences were observed in the metacarpophalangeal joint angles (MT1 and MT2) during jump reception with p≤0.0001 (V 90, V 120, Ox 90, and Ox 120). A p-value of 0.00051 was observed between the angles of V 90 and Ox 120. There was a weak correlation among the evaluated data. The jumping kinematics in BH horses provided insights into flexibility and adaptability during jumps, as well as how the metacarpophalangeal joint angles changed during jump reception.
Keywords:
functional limb; locomotion; joint movements
RESUMO
A cinemática do salto apresenta variação entre raças de cavalos e influencia seu desempenho e sua capacidade atlética. O objetivo deste estudo foi avaliar variações no ângulo da articulação metacarpofalângica durante a recepção do salto em diferentes alturas e larguras pela análise cinemática. Quatorze cavalos Brasileiro de Hipismo (BH) foram avaliados usando-se marcadores refletivos. Saltos verticais de 90 e 120cm de altura (V 90 e V 120) e do tipo oxer com 90 e 120cm de altura (Ox 90 e Ox 120), com uma largura de 100cm, foram examinados. As avaliações dos ângulos da articulação metacarpofalângica ocorreram em dois momentos durante a recepção do salto (MT1 e MT2), quando a articulação alcançou máxima hiperextensão. Diferenças significativas foram observadas nos ângulos da articulação metacarpofalângica (MT1 e MT2) e durante a recepção do salto com P≤0,0001 (V 90, V 120, Ox 90 e Ox 120). Valor de P=0,00051 foi observado entre os ângulos de V 90 e Ox 120. Houve correlação fraca entre os dados avaliados. A cinemática do salto em cavalos BH forneceu informações sobre a flexibilidade e a adaptabilidade durante os saltos, assim como os ângulos da articulação metacarpofalângica alteraram durante a recepção do salto.
Palavras-chave:
membro funcional; locomoção; movimentos articulares
INTRODUCTION
The Brasileiro de Hipismo (BH) breed is relatively recent compared to other breeds, and morphometric assessments have played a significant role in selecting sport horses (Godoi et al., 2013). Understanding the importance of morphological evaluations is crucial for breeders, riders, veterinarians, and other professionals involved in the BH breed, as these assessments represent the initial and pivotal stage in animal selection. Angular measurements have established correlations between functional morphological variables associated with sporting performance, further highlighting the diversity among horses concerning phenotype (Padilha et al., 2017). Conformational characteristics and their alterations have been linked to growth (Santschi et al., 2006) and associated with an increased risk of injuries. Thoroughbreds have shown divergent data due to variations in conformation measurement techniques (Weller et al., 2006).
In equestrian sports, movement, endurance, and movement quality depend on the limbs and joint angles involved. Joint angles exhibit variations corresponding to age (Godoi et al., 2013). The Brasileiro de Hipismo (BH) breed exhibits similarities in certain traits with its foundational breeds, such as wither and croup height, as noted by Rezende et al. (2016). Additionally, Godoi et al. (2013) identified optimal angular values for the fetlock joint in BH horses as 131.7°, 140.9°, and 138.98° for animals aged 22-25 months, 23-32 months, and 36-39 months, respectively. Cunha et al. (2020) determined that for adult animals around nine years old (±3.54 years), minimum values of 149°, maximum values of 170°, and an average of 157.14° were established. When assessing the metacarpophalangeal joint, Unt et al. (2010) found insignificant individual variation between ponies and Thoroughbreds.
The metacarpophalangeal joint plays a pivotal role in equine locomotion, enduring significant stress, particularly during jumping exercises, which can result in injuries and reduced performance. Hence, comprehending the biomechanics of this joint and its response to different jump heights holds considerable importance in equine sports medicine. Building upon previous insights into metacarpophalangeal joint kinetics, asymmetrical activity in thoracic limbs, and the impact of jump height on anatomical structures in athletic horses, this study aims to assess changes in the metacarpophalangeal joint angle during the landing phase of jumps in Brasileiro de Hipismo breed horses across different obstacle heights.
The aim of this investigation is to enhance the current understanding of equine biomechanics in Brasileiro de Hipismo horses. This endeavor seeks to broaden perspectives towards improving performance and minimizing injuries in athletic horses. Through an evaluation of the metacarpophalangeal angle during jump landings, our goal is to further elucidate the functionality of the joint and its potential constraints across different jump heights. Ultimately, such insights may play a pivotal role in enhancing the performance and welfare of equine athletes.
MATERIALS AND METHODS
Fourteen Brasileiro de Hipismo jumping horses, all free from lameness, participated in this study. The group comprised eight males and six females, weighing between 488.8±50.81kg, standing at a height of 1.63±0.03 meters, and aged between 6 and 20 years. Veterinary examinations confirmed the absence of tendon pathologies in all animals, assessed through clinical and ultrasound evaluations. The management approach for these horses was consistent, with access provided to both stalls and paddocks. Training predominantly took place on a sand track, with occasional sessions on a grass track. Their diet consisted of a blend of ration and Tifton hay.
In the competition, horses cleared obstacles at heights ranging from 90cm to 130cm. Seven horses tackled jumps set at 120cm, four at 130cm, two at 110cm, and one at 90cm. A skilled rider was selected, with the combined weight of the rider and equipment at approximately 80 kg. Selection criteria for the horses prioritized optimal health, matched training conditions, and similar diets, ensuring reliable results. The expertise of the rider aided in maintaining consistent jumping execution, reducing the influence of rider skill differences on angle measurements.
To gather the data, a single high-speed video camera was mounted on a tripod approximately three meters from the centre of the obstacle and positioned between one and two meters in front of it (Fig.1). This distance was adjusted to ensure that the jump reception was filmed from the side and centered on the camera (Walker et al., 2018). The camera recorded data at a resolution of 4K (2160p), a frame rate of 960 frames per second (FPS), and a field of view of approximately three meters (Dyson et al., 2018).
View of the measurement locations of the metacarpophalangeal articulations in Brasileiro de Hipismo breed horses. Static (A); hyperextension moment of the thoracic limb 2 (B); hyperextension moment of the thoracic limb 1 (C); angle measurement using software (Smart Tool Factory) (D).
The angle of interest was measured using reflective square markers, each side measuring 10mm, affixed to the left lateral faces. These markers were attached using self-adhesive reflective tape available on the market, similar to the method employed by Godoi et al. (2016), except for the marker size, which was diminished because of the camera's proximity to the limbs. The marker size closely matched that used by Unt et al. (2010). The anatomical locations of interest were identified as the middle thirds of the lateral and medial faces of the hoof coronet, the lateral and medial collateral ligament insertion fossa on the third metacarpal bone, and the ulnar and radial carpal bones (Unt et al., 2010).
Before the recordings, the horses underwent a brief warm-up at a walk, trot, and canter, and jumped over lower obstacles (70cm and 90 cm). All animals worked on the sand track to which they were accustomed. The course included a pole on the ground, followed by an "X"-shaped obstacle at a height of 70cm, a space of 6.5m (allowing for a galloping stride), and the filmed obstacle. The initial jump, shaped like an "X," served as an adjustment jump to minimize variability between animals. The spacing between the reference obstacle and the filmed obstacle allowed for precisely one galloping stride, preventing distance errors during takeoff. The pole on the ground before the "X" marked the takeoff distance for the first jump. The jumps were recorded sequentially: a 90cm vertical (V 90), a 90cm high and 100cm wide oxer (90 Ox), a 120 cm vertical (120 V), and a 120 cm high and 100 cm wide oxer (120 Ox). The kinematic analyzes were conducted at a canter. Each animal jumped over each type of obstacle twice, with jumps in which the poles were knocked down being discarded and repeated. The riders did not indicate the turning side for the animal during the jump. The evaluation occurred in two moments, based on the angle formed between the hoof and metacarpophalangeal joint, taking reception into account. The initial instance occurred when the animal was stationary (MT1 and MT2), standing with all four legs on level ground, devoid of any incline. The subsequent moment transpired during the landing phase of the jump, precisely when the metacarpophalangeal joint approached its nearest position to the ground, exhibiting maximum hyperextension, considering reception.
To analyze the data, jump videos were transferred to a computer and played on Windows Media Player. The videos were then paused at the moment of maximum extension of the metacarpophalangeal joint, following recommendations from the scientific literature (Dyson et al., 2018). The resulting image was saved, and the markers were manually tracked using a high-resolution camera to produce clear images, enabling accurate kinematic evaluation. The Smart Tool Factory® Angle Meter was used to measure the angles of the joint of interest, employing the approach described by Torres-Pérez et al. (2017). Two angle measurements were taken for each type of jump and each limb of the animal, in addition to measurements at rest.
The data underwent descriptive analysis to calculate the mean height, age, and weight. For static angles formed between the hoof and metacarpophalangeal joint (MT1 and MT2) and jumping angles (V 90; V 120; Ox 90; Ox 120), the mean and standard deviation were determined for each. Normality of the angle data was assessed using the Kolmogorov-Smirnov test. Each parameter was then evaluated using a one-way ANOVA, with Tukey's post-test applied. The Pearson correlation test was employed to assess the correlation between thoracic limb angles in a stationary position, comparing them with weight (kg), height (cm), and the angles of different jumps (V 90; V 120; Ox 90; Ox 120). The tests adopted a significance level of p<0.05 (GraphPad Prism Software, San Diego, CA, USA).
RESULTS
The angles for the metacarpophalangeal joint ranged from 140.17° to 162.37°, with a mean of 151.35±6.44°. The values obtained for thoracic limb 1 at the highest hyperextension moment (Table 1) were 117.2±7.14°, 112.8±4.98°, 114.9±5.92°, and 111.6±5.56° for V 90, V 120, Ox 90, and Ox 120, respectively. Significant differences were observed in the comparison between stationary and jumping evaluations (p≤0.00001), as well as between V 90 and Ox 120 (p=0.00051) after statistical testing (Fig. 2).
The percentage variation between the means when comparing stationary and jumping positions was 22.5% (between the station and V 90) and 26.3% (between the station and Ox 120). Among the jumping data, the mean variation ranged from 1.1% (between V 120 and Ox 120) to 4.8% (between V 90 and Ox 120) (Table 1).
For the evaluation of thoracic limb 2 (Tab.2), the mean angles for V 90, V 120, Ox 90, and Ox 120 were 125.1±6.8°, 123.7±8.2°, 123.2±8.6°, and 121.7±6.9°, respectively. Significant differences were observed between the stationary and jumping positions for thoracic limb 2 (p≤0.00001), but no significant differences were found between the different jumping conditions (Fig. 2).
The percentage variation of the angles when comparing stationary and jumping positions was 17.36% (between the station and V 90) and 19.56% (between the station and Ox 120). Among the jumping conditions, the mean variation ranged from 0.46% (between V 120 and Ox 120) to 2.65% (between V 90 and Ox 120), and 2.65% (between V 120 and Ox 120) (Table 2).
Representation of metacarpophalangeal joint angles in Brasileiro de Hipismo breed horses at rest and hyperextension. Thoracic limb 1 in station (MT1) (A); Thoracic limb 2 in station (MT2) (B); 90 cm vertical (V 90); 120 cm vertical (V 120); 90 cm height oxer (Ox 90); and 120 cm height oxer (Ox 120). One-way ANOVA, followed by Tukey's post-test, was applied, p<0.05.
Metacarpophalangeal joint angles of Brasileiro de Hipismo breed horses at rest and hyperextension. Thoracic limb 1 in station (MT1); 90cm vertical (V 90); 120cm vertical (V 120); 90cm height oxer (Ox 90); and 120cm height oxer (Ox 120). One-way ANOVA, with Tukey's post-test applied, p<0.05
Metacarpophalangeal joint angles of Brasileiro de Hipismo breed horses at rest and hyperextension. Thoracic limb 2 in station (MT2); 90cm vertical (V 90); 120cm vertical (V 120); 90cm height oxer (Ox 90); and 120cm height oxer (Ox 120). One-way ANOVA, followed by Tukey's post-test, was applied, p<0.05
The findings from applying the Pearson correlation test revealed weak associations among thoracic limb angles in a stationary position when compared with weight (kg), height (cm), and the angles of various jumps (V 90; V 120; Ox 90; Ox 120) (Fig.3). Examining the significance thresholds (p<0.05), solely the Ox 120 angle and the metacarpophalangeal joint in station exhibited a significant difference p=0.03 (Fig.3).
Representative graphs of the application of the Pearson correlation test in Brasileiro de Hipismo breed horses between the angles of the Thoracic limb in a stationary position; Weight (Kg) (A); Height (cm) (B); 90 cm vertical (V 90) (C); 120 cm vertical (V 120) (D); 90 cm height oxer (Ox 90) (E); and 120 cm height oxer (Ox 120) (F). Pearson correlation test (r), p<0.05.
DISCUSSION
It is plausible to suggest that joint angles in horses may vary based on age. Considering the role of bones as levers that facilitate movement in conjunction with flexor muscle, a study by Godoi et al. (2013) determined the metacarpophalangeal angle for Brasileiro de Hipismo (BH) horses in a stationary position. The study found mean angles of 131.7°, 140.9°, and 138.98° for animals aged between 22-25, 23-32, and 36-39 months, respectively. Another study with adult BH horses aged between 5.46 and 12.54 years (Cunha et al., 2020) reported a minimum angle value of 149°, a maximum of 170°, and a mean of 157.14°. In the present study, also conducted with adult BH horses (mean age of 8.4 years), the angles in a stationary position varied between 140.17° and 162.17°, with a mean of 151.35±6.32°. Previous research with young BH horses demonstrated that kinematic analysis provided an objective assessment of morphology and locomotion (Godoi et al., 2016). The values obtained in studies with adult horses differed significantly from those found in younger horses of the same breed, suggesting that age may indeed influence joint angles. The association of conformational characteristics with growth and the risk of injuries is deemed crucial (Santschi et al., 2006). Studies have indicated that genetic grouping, sex, and the interaction between groups contribute to variations (P<0.05) in conformation indices (Rezende et al., 2016). However, all studies with adult horses showed differences in the minimum and maximum angles, suggesting that factors beyond age, such as individual variability, may play a role.
Conformation, referring to the structural arrangement of body segments, including their relationships, angles, and deviations, serves as an indicator of the athletic ability of horses (Unt et al., 2010). In a study by Unt et al. (2010), the angle of the metacarpophalangeal joint varied from 176.7° to 182.4° while the horses were standing, walking, and trotting. The observed variation in the minimum angle between the study conducted by Cunha et al. (2020) and the present study can be attributed to differences in breeds. The BH breed is characterized by its broad scope, allowing the use of mares and stallions from other breeds, provided that the breeding process adheres to the guidelines of the association governing the BH breed. Animals evaluated in studies by Unt et al. (2010) and Cunha et al. (2020) suggest that breed and lineage may indeed influence joint angles. It is worth noting that the greatest angular deviations in the metacarpophalangeal joint are often associated with technical errors, such as incorrectly positioned markers (Weller et al., 2006). Comprehensive linear schemes outlining joint angular measurements have proven crucial in establishing performance indices related to phenotypes and the heterogeneity of sport horses (Padilha et al., 2017).
Concerning the thoracic limb 1 and 2 in BH horses, there was a significant difference between the values in the stationary position and all the jumps performed. The differences between the angular means of each type of jumping compared to the stationary position were higher for the thoracic limb 1 than the thoracic limb 2, and they were even more pronounced for different heights or widths. The mean angular differences found when compared to the stationary position were (grouping all types of jumps) 37.21±2.48° for the thoracic limb 1 and 27.92±1.38° for the thoracic limb 2.
In equines, a positive correlation was observed between ground reaction force and the palmar angle of the metacarpophalangeal joint during walking, trotting, and galloping; in other words, an increase in the angle corresponded to an increase in force (McGuigan and Wilson, 2003). When assessing jumping and its impact on tendons, an increase in ground reaction force was noted with the elevation of jump height at different levels of 80 cm, 100 cm, and 120 cm (Meershoek et al., 2001). In the comparison of different jumps, significant differences were observed in the angles of the thoracic limbs at rest compared to the angles in various jumps, particularly when comparing a 90 cm vertical jump to a 120 cm oxer. The increase in ground reaction force due to the jump indicates that BH horses were well-suited for the exercise. This is attributed to the decrease in ground reaction force resulting from shorter support time (Unt et al., 2010), which in turn alters the evaluated angles during jumps.
Between jumps, there was no rise in the angles of hyperextension of the metacarpophalangeal joint when adjusting the complexity of the jump, whether by widening or heightening it, in most cases. This constraint was determined by the extension capacity of the metacarpophalangeal joint. Even without assessing the initial and final angles during the jump, there was a variation of approximately 40° during the support phase of landing (Meershoek et al., 2001). A weak correlation was observed between the angles of the thoracic limb in a stationary position and the angles obtained upon landing from the jumps (V 90, V 120, Ox 90, and Ox 120).
The lack of a significant difference observed in comparing various jumps might explain the athletic ability of BH horses. This suggests that the angle of the scapulohumeral joint could be a valuable variable in determining suitability for jumping (Godoi et al., 2013). The angle of this joint influenced neck extension and flexion of the thoracic limbs during obstacle jumps (Godoi et al., 2013). This aspect is crucial in assessing the suitability of jumping equines, coupled with evaluating impact absorption during landing, as all the anatomical parts involved are interconnected.
The support and stabilization of the metacarpophalangeal joint during locomotion relies on the suspensory apparatus, which includes the interosseous muscle associated with the deep and superficial digital flexor tendons. This apparatus prevents excessive hyperextension when the hoof contacts the ground (McGuigan and Wilson, 2003). Equines have evolved tendinous support mechanisms, both static and dynamic, enabling the species to sustain its body weight with minimal muscular effort, thereby reducing the risk of injuries (Unt et al., 2010). The dorsal angle of the metacarpophalangeal joint decreased with increased jump difficulty, showing reductions of 1.1% to 4.8% for the thoracic limb 1 (MT1) and between 0.46% and 2.65% for the thoracic limb 2 (MT2). Tendinous fatigue was responsible for greater joint hyperextension, along with modifications in the myotendinous junction related to movement.
The metacarpophalangeal joint is the only joint capable of modifying length distally by altering bone-tendon tension, predicting the force imposed on the limb (McGuigan and Wilson, 2003). In understanding the angular amplitudes of the evaluated joints, the works of Watanabe et al. (2004) and Johnston et al. (2010) were highlighted. The Golgi tendon organ (GTO) acts as the mechanoreceptor responsible for protecting the muscle from overload (Watanabe et al., 2004). The action of the myotendinous junction might be one of the determining factors in increased fatigue-induced hyperextension (Johnston et al., 2010), additionally, these findings could also be relevant to the animals under study. The variations among different angles observed for the metacarpophalangeal joint could be explained using BH horses in an advanced training phase, demonstrating proven athletic ability and appropriate training.
The stride frequencies and estimates of limb stiffness decreased during fatigue; however, it remains undetermined whether these changes are advantageous or disadvantageous in terms of energy or injury (Wickler et al., 2006). In a study where trotting horses were exercised on a treadmill until they were unwilling to keep up with their pace, fatigue increased the hyperextension of the metacarpophalangeal joint by up to 8 degrees (Johnston et al., 2010). However, the observed variation of more than 4.85% in the Brasileiro de Hipismo showjumping horses was greater than 5.68 degrees, indicating a notable adaptation in the metacarpophalangeal joint during jump landings. This difference may be attributed to the distinct breeds assessed or the intensity of the exercise imposed (Johnston et al., 2010).
CONCLUSIONS
The ability of the Brasileiro de Hipismo breed horse to functionally adapt the metacarpophalangeal joint during jump landings was remarkable. Kinematic analysis of the angle played a crucial role in evaluating the amplitude of this landing, emphasizing the importance of proper training and conditioning for these animals to enhance their performance. These factors were decisive in assessing the athletic ability of the Brasileiro de Hipismo breed horse, particularly considering the effects generated by the required movements.
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Publication Dates
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Publication in this collection
28 Apr 2025 -
Date of issue
May-Jun 2025
History
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Received
19 Apr 2024 -
Accepted
19 Sept 2024
