Dynamic mobilisations in cervical flexion: Effects on intervertebral angulations

Hyperflexing the horse's neck: a systematic review and meta-analysis

The article reports a meta-analysis of 58 peer-reviewed studies investigating on dorsoventral hyperflexion of the neck in horses, a practice under substantial public and scientific scrutiny for the past two decades. The following databases were last searched on 28.05.2023: CAB, Google Scholar, Web of Science, NAL/Agricola, PubMed and ScienceDirect. After evaluating the conclusions of each study, we performed statistical analyses to establish a consensus on welfare and performance (performance marks, kinematics and musculoskeletal) outcomes in horses performing with a hyperflexed head and neck posture (HNP). The analysis revealed that a significant majority of the articles (75% of n = 36; Z = 3.00; P>|Z|=0.0027) expressed concerns about the welfare of horses working in this posture. Parameters such as dressage training level, prior experience, duration, and method of achieving the hyperflexed posture did not influence welfare concern conclusions significantly (P > 0.1). Therefore, it appears that the practice impairs welfare regardless of how it is imposed. A concurrent assessment of the weight of evidence for performance benefits showed inconclusive results: approximately one-quarter of the studies showed benefits and one-quarter detrimental effects, while the largest proportion (44%) showed no significant effect on performance. On balance, it appears that the costs associated with hyperflexed HNPs exceed potential benefits.

The Effect of Chiropractic Treatment on Limb Lameness and Concurrent Axial Skeleton Pain and Dysfunction in Horses

Chiropractic care is a common treatment modality used in equine practice to manage back pain and stiffness but has limited evidence for treating lameness. The objective of this blinded, controlled clinical trial was to evaluate the effect of chiropractic treatment on chronic lameness and concurrent axial skeleton pain and dysfunction. Two groups of horses with multiple limb lameness (polo) or isolated hind limb lameness (Quarter Horses) were enrolled. Outcome measures included subjective and objective measures of lameness, spinal pain and stiffness, epaxial muscle hypertonicity, and mechanical nociceptive thresholds collected on days 0, 14, and 28. Chiropractic treatment was applied on days 0, 7, 14, and 21. No treatment was applied to control horses. Data was analyzed by a mixed model fit separately for each response variable (p < 0.05) and was examined within each group of horses individually. Significant treatment effects were noted in subjective measures of hind limb and whole-body lameness scores and vertebral stiffness. Limited or inconsistent therapeutic effects were noted in objective lameness scores and other measures of axial skeleton pain and dysfunction. The lack of pathoanatomical diagnoses, multilimb lameness, and lack of validated outcome measures likely had negative impacts on the results.

The Effect of Capacitive-Resistive Electrical Therapy on Neck Pain and Dysfunction in Horses

Neck pain and stiffness are increasingly recognized in horses and often treated using multimodal pharmaceutical and rehabilitation approaches. In humans, deep tissue heating is reported to reduce neck pain and increase flexibility. The objective of this project was to determine the effects of capacitive-resistive electrical therapy on neck pain and stiffness in horses. A blinded, randomized, controlled clinical trial with 10 horses assigned to active and 10 horses assigned to sham treatment groups. Neck pain, stiffness, and muscle hypertonicity were assessed by manual palpation. Forelimb postural stability was evaluated using a portable media device with built-in inertial sensing components. All outcome parameters were recorded once weekly for four weeks. Using manufacturer recommendations, the treatment group received active capacitive-resistive electrical therapy to the lower cervical region (C4-C7), twice weekly for a total of six treatments, while the control group received a sham (inactive) treatment. Data was analyzed using a mixed model that was fit separately for each response variable. There were no significant differences noted over time or between groups for any outcome parameter evaluated. While neck pain and stiffness decreased by week three in both groups, the improvement was not significant. Limitations include the lack of a definitive pathoanatomic diagnosis of cervical pathology and in vivo temperature measurements. Capacitive-resistive electrical therapy was ineffective in reducing neck pain and dysfunction using the recommended treatment protocols. No short-term adverse effects were noted. Specific clinical applications and effective treatment parameters need further evaluation.

Rehabilitation Strategies for the Neurologic Horse

Rehabilitation of the neurologic horse represents a unique challenge for the equine practitioner. Improving postural stability and balance control through improving the strength of the spinal stabilizer muscle multifidus remains one of the most promising rehabilitative targets. This muscle can be targeted through the use of physiotherapeutic exercises, various forms of perturbation, and even whole-body vibration. Neuroanatomic localization and diagnosis specificity enable the practitioner to determine suitability for such rehabilitative tasks, and with the advent of evolving strategies and commercially available equipment, the bandwidth for professionally guided programs is continuously being developed and is expected to improve traditional outcomes.

Equine Rehabilitation: A Scoping Review of the Literature

Simple Summary

When a horse is diagnosed with a locomotor disorder, the veterinarian treats the specific injury to restore the horse to soundness. Even after the injury has healed, however, the horse may not be fully functional due to persistent limitations in movement or strength in specific areas of the body. As in people, rehabilitation seeks to optimize function and reduce any existing disability using a variety of methods including manual therapy, the use of physical and mechanical agents, and specialized exercise regimes. This study has reviewed the scientific literature with the goal of identifying which types of physical therapy have been described in horses over the past 20 years. The most frequently reported techniques were exercise, electrotherapy, and hydrotherapy but there are relatively few publications describing details of their use and outcomes in clinical cases. This study reviews the methodology and outcomes of rehabilitation in clinical cases. The results highlight the paucity of clinically-based reports on the practical applications of equine rehabilitation and physical therapy.

Abstract

Injuries to the locomotor system are a common problem in athletic horses. Veterinarians address these injuries using appropriate medical, surgical, and pharmacological treatments. During or after recovery from the initial injury, horses may be treated for functional locomotor deficits using specific rehabilitation techniques aimed at restoring full athletic performance. This study reviews the literature to identify which rehabilitative techniques have been used most frequently in horses over the past 20 years, the protocols that were used, and the outcomes of the treatments in naturally occurring injuries and diseases. Publications were identified using keyword selection (Equine Athlete OR Equine OR Horse) AND (Rehabilitation OR Physiotherapy OR Physical Therapy). After removing duplicates and screening papers for suitability, 49 manuscripts were included in the study. The majority of publications that met the inclusion criteria were narrative reviews (49%) in which the authors cited the relatively small number of published evidence-based studies supplemented by personal experience. Observational/descriptive studies were also popular (35%). Randomized control trials accounted for only 10%. The most frequently reported rehabilitation techniques were exercise, electrotherapy, and hydrotherapy. The findings highlight the need for further information regarding type of intervention, parameterization, and outcomes of equine rehabilitation in clinical practice.

Equine Cervical Pain and Dysfunction: Pathology, Diagnosis and Treatment

Simple Summary

Neck pain and dysfunction in the horse is becoming an increasingly important topic among riders, trainers and veterinarians. Some horses may present for a subtle performance decline, while others may show dramatic, dangerous behavior. It is important to recognize how to carefully evaluate the horse in an effort to understand the different types of pain that may be contributing to the different behaviors. The musculoskeletal and nervous systems may both play a role in the development of clinical signs. Recognizing that there are many diagnostic options as well as several treatments choices is important. This synopsis covers the disease processes that may contribute to the development of neck pain and dysfunction in the horse, as well as several possible diagnostic and treatment options.

Abstract

Interest in the cervical spine as a cause of pain or dysfunction is increasingly becoming the focus of many equine practitioners. Many affected horses are presented for poor performance, while others will present with dramatic, sometimes dangerous behavior. Understanding and distinguishing the different types of neck pain is a starting point to comprehending how the clinical presentations can vary so greatly. There are many steps needed to systematically evaluate the various tissues of the cervical spine to determine which components are contributing to cervical pain and dysfunction. Osseous structures, soft tissues and the central and the peripheral nervous system may all play a role in these various clinical presentations. After completing the clinical evaluation, several imaging modalities may be implemented to help determine the underlying pathologic processes. There are multiple treatment options available and each must be carefully chosen for an individual horse. Provided is a synopsis of the current knowledge as to different disease processes that can result in cervical pain and dysfunction, diagnostic approaches and treatment strategies. Improving the knowledge in these areas will ideally help to return horses to a state of well-being that can be maintained over time and through the rigors of their job or athletic endeavors.

The Effect of a Physiotherapy Intervention on Thoracolumbar Posture in Horses

Dynamic mobilisation exercises (DME) are often used as part of a physiotherapy rehabilitation programme. Whilst immediate kinematic effects have been measured, the change in posture is anecdotally reported to have a longer duration. This study aimed to test the reliability of a simple objective measurement method, suitable for use in clinical practice, and to objectively measure equine thoracolumbar posture, before and after DME. A single investigator took triplicate measurements of the sagittal thoracolumbar shape using a flexicurve ruler (FCR) then triplicate measurements of the thoracolumbar shape using an adapted FCR (aFCR) in 37 horses. Subsequently, the thoracolumbar shape of 12 horses was measured using the aFCR before random allocation into two groups. Six horses acted as a control group and six horses underwent a series of DME, which included cervical flexion and lateral flexion baited stretches. Measurements were repeated prior to DME, at thirty minutes, one hour and at twenty-four hours after DME to assess thoracolumbar posture. The aFCR ruler had excellent intra-rater reliability compared to a standard FCR (aFCR: p = 0.146; intraclass correlation coefficient (ICC) 0.971; FCR: p = 0.0001; ICC 0.979). Significant increases in flexion occurred in the thoracolumbar region at 30 min (p = 0.027) and one hour (p = 0.046) after DME, but not at 24 h (p > 0.05) with no significant differences in the control group (p > 0.05) between baseline and subsequent times. The results suggest DME create a short-term postural change, determined by using an aFCR, which supports their use as part of a veterinary physiotherapy rehabilitation programme.

Objective measurement in equine physiotherapy

Objective measurement should be incorporated into all areas of physiotherapy including within the assessment and treatment of horses, as there is a need to evaluate the effectiveness of treatment intervention objectively. Whilst objective measures are available in a research laboratory setting it appears that in clinical practice mostly subjective methods of recording assessment and reassessment data are used. This article reviews the objective measures currently available to equine physiotherapists for use in clinical practice, beyond those available in a research laboratory setting. Within the literature there are studies reporting the reliability and validity of objective measures for the assessment of pain, gait, posture, range of motion, palpation and muscle size in horses. Whilst these validated objective measurement tools are available, they are not presently used consistently in clinical practice. In addition, the non-verbal nature of the equine patients precludes the use of self-reporting, meaning that there are no reported functional outcome scores possible similar to use with human patients. However, the combined use of pain responses, behavioural changes and objective measures collected during clinical assessment, both pre and post treatment, could be useful in practice. Equine physiotherapists should integrate more objective methods of recording data from assessments of horses.

Generation of Domains for the Equine Musculoskeletal Rehabilitation Outcome Score: Development by Expert Consensus

Simple Summary

Within rehabilitation, measurements taken before, during and after treatments are used to judge patient progress and the effectiveness of prescribed treatments. To know which measurements to use for a given health condition, practitioners must have knowledge of what should be measured, which measurement tools are available and accurate, alongside what they intend to measure. Composite outcome measures (OMs) are tools which use grouped measurement tests to monitor patient progress; they have been tested for a variety of human and canine conditions but none have been designed or tested for use in physical rehabilitation in horses. This study asked leading equine veterinarians, physiotherapists and researchers which measures should be included in an OM for use in the rehabilitation of horses. Using a process to evaluate agreement, ten areas of measurement were included in the final model: lameness, pain at rest, pain during exercise, behaviour during exercise, muscular symmetry, performance/functional capacity, behaviour at rest, palpation, balance and proprioception. Existing reliable tests used to measure these areas were evaluated and potential new measures discussed and now should be taken forward to testing as a composite outcome score to see if they are effective in measuring effectiveness of treatment.

Abstract

Outcome measures (OMs) are a requirement of professional practice standards in human and canine physiotherapy practice for measurement of health status. Measures such as pain and functional capacity of specific regions are used to track treatment impact and can be used to develop optimal management strategies. To achieve comparable patient care in equine physiotherapy, OMs must be incorporated into practice; however, no reliable and valid OMs exist for equine rehabilitation. This study utilised the experience and opinion of a panel of experts working in the equine rehabilitation sphere to gain consensus on the core areas (domains) to be included in a model, to lead to an OM scale for horses undergoing rehabilitation. The Delphi method and content validity ratio testing was used to determine agreement with domains reaching the critical value required for inclusion. The expert panel agreed on ten domains to be included in the OM scale: lameness, pain at rest, pain during exercise, behaviour during exercise, muscular symmetry, performance/functional capacity, behaviour at rest, palpation, balance and proprioception. An OM with these domains would provide a holistic objective assessment tool which could be used by equine rehabilitation professionals in clinical practice.

An equine cadaver study investigating the relationship between cervical flexion, nuchal ligament elongation and pressure at the first and second cervical vertebra

Pressure in the atlanto-axial region due to hyperflexion ('rollkur') may influence the development of a nuchal bursa, as adventitious bursae may be caused by pressure. Investigating the pressure between the nuchal ligament and atlas/axis in a flexed position may provide information on the pathogenesis of nuchal bursitis. In this study, ten equine head and neck specimens with one side of the soft tissues over the cervical vertebral spine removed were placed in lateral recumbency on a table in neutral, mildly flexed, and hyperflexed head and neck positions. Angulations of the neck were measured using markers placed on the nuchal ligament and drilled into the skull, vertebrae and withers. In six specimens, the pressure between the nuchal ligament and the atlas and the axis was measured using an inflatable air pouch. Hyperflexion was associated with the highest nuchal ligament length and with the highest pressure values at the site of the nuchal bursa over the atlas (99±24mmHg, more than four times the pressure in the neutral position) and over the axis (77±30mmHg, more than twice the pressure values of the neutral position). Also, over the three head and neck positions, neck flexion angles were highly correlated with pressure values and with nuchal ligament length. This marked increase in pressure at the level of atlas and axis caused by head and neck hyperflexion should be considered during training of horses at risk of, or diagnosed with, nuchal bursitis.

CT measures of lumbosacral paraspinal muscle size are not correlated with CT measures of lumbosacral stability in military working Labrador Retrievers

Management of degenerative lumbosacral stenosis in military working dogs more frequently utilizes core conditioning exercise programs. Future research on the effectiveness of these programs may benefit from an improved understanding of relationships between paraspinal muscle size and lumbosacral stability. The aim of this retrospective, secondary analysis, cross-sectional study was to test the following hypotheses related to CT measures: (a) transverse paraspinal muscle area ratios differ between hip flexion and extension, (b) lumbosacral angle and lumbosacral range of motion differ by lumbosacral angle measurement technique, and (c) transverse paraspinal muscle area ratios are correlated with CT measures of lumbosacral stability (parasagittal and parasagittal oblique foraminal area changes) regardless of hip position and with lumbosacral range of motion within each hip position. Lumbosacral CT scans in hip flexion and extension were retrieved from a previous prospective study of military working Labrador Retrievers. A single observer performed triplicate measurements of transverse paraspinal muscle area ratios, parasagittal foraminal area, and parasagittal oblique foraminal area for each hip position and another observer independently performed triplicate measurements of lumbosacral angle and lumbosacral range of motion at L7-S1 using two published techniques. Thirty-nine dogs were analyzed and significant differences were identified between hip flexion and extension for all mean transverse paraspinal muscle area ratio values (P ≤ .05). Mean lumbosacral angles also significantly differed between the published techniques in both hip flexion and extension. When comparing mean lumbosacral range of motion values, one of the published techniques produced significantly smaller values. No significant correlation was found between transverse paraspinal muscle area ratios and parasagittal foraminal area changes, parasagittal oblique foraminal area changes, or lumbosacral range of motion. These results should be considered when designing studies using these CT measures in military working dogs.

The Disappearing Lamellae: Implications of New Findings in the Family Equidae Suggest the Loss of Nuchal Ligament Lamellae on C6 and C7 Occurred After Domestication

Conflicting data predominantly describes the equine nuchal ligament lamellae (NLL) attachments as C2-C6 or C2-C7; however, preliminary evidence suggests C2-C5. This study aimed to identify morphological variations in the attachments of the NLL in four species of the family equidae and determine if the variations were species or breed linked. Cadaveric examination evaluated 98 equids; Equusasinus (n = 2), Equus ferus caballus (n = 93), Equus przewalskii (n = 2), and Equus quagga boehmi (n = 1). Twenty breeds of E. f. caballus were included according to breed type-modern horse (n = 81), ancient type (n = 10), primitive (n = 4). Of the 98 equids, observations were divided into three categories according to the NLL attachments: C2-C5, C2-C6, and C2-C7; in category C2-C7, E. f. caballus (n = 3/93), modern horse 0 of 81, ancient 1 of 8, primitive 2 of 4; in category C2-C6, modern horse 2 of 81; in category C2-C5, modern horse 79 of 81, ancient type 7 of 8, primitive 2 of 4. Equus asinus, E. przewalskii, and E. q. boehmi all expressed category C2-C7. In total, 88 of 98 expressed category C2-C5; 2 of 98 category C2-C6; and 8 of 98 category C2-C7. These findings suggest that category C2-C5 provides sufficient evidence to suggest a normal occurrence. The high incidence of an absent NLL on C6 and C7 may be considered a contributing factor in caudal cervical osteoarthritis. Furthermore, category C2-C7 still exists in an ancient and primitive breed closely related to the tarpan, implying the NLL may have been attached from C2 to C7 in prehistoric horse before domestication. This hypothesis is supported by the findings of E. asinus, E. przewalskii, and E. q. boehmi, displaying attachments from C2 to C7.

Intervertebral Disc Degeneration in Warmblood Horses: Morphology, Grading, and Distribution of Lesions

Equine intervertebral disc degeneration is thought to be rare and of limited clinical relevance, although research is lacking. To objectively assess pathological changes of the equine intervertebral disc and their clinical relevance, description of the normal morphology and a practical, biologically credible grading scheme are needed. The objectives of this study are to describe the gross and histological appearance of the equine intervertebral discs and to propose a grading scheme for macroscopic degeneration. Spinal units from 33 warmblood horses were grossly analyzed and scored. Of the 286 intervertebral discs analyzed, 107 (37%) were assigned grade 1 and grade 2 (considered normal) and were analyzed histologically. A nucleus pulposus and an annulus fibrosus could be identified macroscopically and histologically. Histologically, the nucleus pulposus was composed of a cartilaginous matrix and the annulus fibrosus of parallel collagenous bands. A transition zone was also histologically visible. Intra- and inter-observer reliability scores were high for all observers. Higher grades were associated with greater age. Gross changes associated with equine intervertebral disc degeneration (grades 3-5)-that is, yellow discoloration, cleft formation (tearing), and changes in consistency of the nucleus pulposus-were largely similar to those in humans and dogs and were most prevalent in the caudal cervical spine. Equine intervertebral disc degeneration was not associated with osteophyte formation. Changes of the vertebral bone were most common in the thoracolumbar spine but were not correlated with higher grades of intervertebral disc degeneration. Thus, changes of the vertebral bone should be excluded from grading for equine intervertebral disc degeneration.

Core Training and Rehabilitation in Horses

The central body axis or core is a key component in controlling body posture and providing a stable platform for limb movements and generation of locomotor forces. Persistent dysfunction of the deep stabilizing muscles seems to be common in horses indicating a need for core training exercises to restore normal function. Core training should be performed throughout the horse's athletic career to maintain a healthy back and used therapeutically when back pain is identified. This article reviews the structure and function of the equine thoracolumbar spine with special reference to function, dysfunction, conditioning, and rehabilitation of the core musculature.

Current Welfare Problems Facing Horses in Great Britain as Identified by Equine Stakeholders

Despite growing concerns about the welfare of horses in Great Britain (GB) there has been little surveillance of the welfare status of the horse population. Consequently we have limited knowledge of the range of welfare problems experienced by horses in GB and the situations in which poor welfare occurs. Thirty-one in-depth interviews were conducted with a cross -section of equine stakeholders, in order to explore their perceptions of the welfare problems faced by horses in GB. Welfare problems relating to health, management and riding and training were identified, including horses being under or over weight, stabling 24 hours a day and the inappropriate use of training aids. The interviewees also discussed broader contexts in which they perceived that welfare was compromised. The most commonly discussed context was where horses are kept in unsuitable environments, for example environments with poor grazing. The racing industry and travellers horses were identified as areas of the industry where horse welfare was particularly vulnerable to compromise. Lack of knowledge and financial constraints were perceived to be the root cause of poor welfare by many interviewees. The findings give insight into the range of welfare problems that may be faced by horses in GB, the contexts in which these may occur and their possible causes. Many of the problems identified by the interviewees have undergone limited scientific investigation pointing to areas where further research is likely to be necessary for welfare improvement. The large number of issues identified suggests that some form of prioritisation may be necessary to target research and resources effectively.

Spinal Motion and Muscle Activity during Active Trunk Movements - Comparing Sheep and Humans Adopting Upright and Quadrupedal Postures

Sheep are used as models for the human spine, yet comparative in vivo data necessary for validation is limited. The purpose of this study was therefore to compare spinal motion and trunk muscle activity during active trunk movements in sheep and humans. Three-dimensional kinematic data as well as surface electromyography (sEMG) of spinal flexion and extension was compared in twenty-four humans in upright (UR) and 4-point kneeling (KN) postures and in 17 Austrian mountain sheep. Kinematic markers were attached over the sacrum, posterior iliac spines, and spinous and transverse processes of T5, T8, T11, L2 and L5 in humans and over the sacrum, tuber sacrale, T5, T8, T12, L3 and L7 in sheep. The activity of erector spinae (ES), rectus abdominis (RA), obliquus externus (OE), and obliquus internus (OI) were collected. Maximum sEMG (MOE) was identified for each muscle and trial, and reported as a percentage (MOE%) of the overall maximally observed sEMG from all trials. Spinal range of motion was significantly smaller in sheep compared to humans (UR / KN) during flexion (sheep: 6–11°; humans 12–34°) and extension (sheep: 4°; humans: 11–17°). During extension, MOE% of ES was greater in sheep (median: 77.37%) than UR humans (24.89%), and MOE% of OE and OI was greater in sheep (OE 76.20%; OI 67.31%) than KN humans (OE 21.45%; OI 19.34%), while MOE% of RA was lower in sheep (21.71%) than UR humans (82.69%). During flexion, MOE% of RA was greater in sheep (83.09%) than humans (KN 47.42%; UR 41.38%), and MOE% of ES in sheep (45.73%) was greater than KN humans (14.45%), but smaller than UR humans (72.36%). The differences in human and sheep spinal motion and muscle activity suggest that caution is warranted when ovine data are used to infer human spine biomechanics.

The equine neck and its function during movement and locomotion

During both locomotion and body movements at stance, the head and neck of the horse are a major craniocaudal and lateral balancing mechanism employing input from the visual, vestibular and proprioceptive systems. The function of the equine neck has recently become the focus of several research groups; this is probably also feeding on an increase of interest in the equine neck in equestrian sports, with a controversial discussion of specific neck positions such as maximum head and neck flexion. The aim of this review is to offer an overview of new findings on the structures and functions of the equine neck, illustrating their interplay. The movement of the neck is based on intervertebral motion, but it is also an integral part of locomotion; this is illustrated by the different neck conformations in the breeds of horses used for various types of work. The considerable effect of the neck movement and posture onto the whole trunk and even the limbs is transmitted via bony, ligamentous and muscular structures. Also, the fact that the neck position can easily be influenced by the rider and/or by the employment of training aids makes it an important avenue for training of new movements of the neck as well as the whole horse. Additionally, the neck position also affects the cervical spinal cord as well as the roots of the spinal nerves; besides the commonly encountered long-term neurological effects of cervical vertebral disorders, short-term changes of neural and muscular function have also been identified in the maximum flexion of the cranial neck and head position. During locomotion, the neck stores elastic energy within the passive tissues such as ligaments, joint capsules and fasciae. For adequate stabilisation, additional muscle activity is necessary; this is learned and requires constant muscle training as it is essential to prevent excessive wear and tear on the vertebral joints and also repetitive or single trauma to the spinal nerves and the spinal cord. The capability for this stabilisation decreases with age in the majority of horses due to changes in muscle tissue, muscle coordination and consequently muscle strength.

Evaluation of skin displacement in the equine neck

Kinematic studies, using reflective skin markers, are commonly used to investigate equine joint motion in equitation science and for rehabilitation purposes. In order to interpret the registrations accurately, the degree of skin displacement has been described for the limbs and back, but not yet for the neck. The aim of the present study was to measure sagittal plane skin displacement in the equine neck. Radiopaque skin markers were applied to the skin over the first six cervical vertebrae of six healthy horses. Latero-lateral radiographs were taken in three standardised neck positions in the sagittal plane: control (horizontal neck), ‘on the bit’ and ‘nose to carpus’. The scales of the images were normalised and calculation of skin displacement was done by use of a coordinate system, dividing the displacement along an x-axis parallel to the vertebra's longitudinal axis and a y-axis perpendicular to the x-axis. Mixed models analysis was employed to study the differences in distances in x- and y-directions, and statistical significance was set to PÃ0.05. Between control and ‘nose to carpus’ positions, there were significant differences in skin marker locations, relative to the underlying vertebrae, in the x-direction for C1-6, and in y-direction for C3-6. Between normal and ‘on the bit’ positions, there were significant difference in both x- and y-directions for C6. Differences in marker locations along x- and y-axes, respectively, were 3±9 mm and 44±14 mm. The outcome of this study indicates that skin displacement should be considered when investigating equine neck motion with skin marker methodology.

Dynamic mobilisation exercises increase cross sectional area of musculus multifidus

REASON FOR PERFORMING STUDY

In human subjects with back pain, the deep spinal stabiliser m. multifidus is inhibited ipsilaterally leading to atrophy, asymmetry and intervertebral instability. Specific physiotherapeutic exercises are required to reactivate m. multifidus. This study assesses the effect of dynamic mobilisation exercises on size and symmetry of m. multifidus in the equine caudal thoracic and lumbar spine.

HYPOTHESES

Regular performance of dynamic mobilisation exercises over a period of 3 months increases cross sectional area (CSA) and left-right symmetry of m. multifidus muscles in the caudal thoracic and lumbar spine.

METHODS

Eight horses performed dynamic mobilisation exercises (3 cervical flexions, one cervical extension and 3 lateral bending exercises to the left and right sides) with 5 repetitions/exercise/day on 5 days/week for 3 months during which time they were not ridden. Left and right m. multifidus CSA was measured ultrasonographically at 6 levels from T10 to L5 at the start (initial evaluation) and end (final evaluation) of the 3 month study. Changes in CSA of the right and left m. multifidus muscles and symmetry of m. multifidus CSA on the right and left sides between the 2 evaluations were sought using analysis of variance (P<0.05).

RESULTS

Between the initial evaluation and final evaluation m. multifidus CSA increased significantly at all 6 spinal levels on both right and left sides. Asymmetries in m. multifidus CSA between the right and left sides decreased between the initial and final evaluations.

CONCLUSIONS

Hypertrophy of multifidus occurred over a 3 month period during which dynamic mobilisation exercises were the only exercise performed.

POTENTIAL RELEVANCE

Dynamic mobilisation exercises maybe a useful rehabilitative technique for horses in which m. multifidus has atrophied in response to back pain.

Length and elasticity of side reins affect rein tension at trot

This study investigated the horse's contribution to tension in the reins. The experimental hypotheses were that tension in side reins (1) increases biphasically in each trot stride, (2) changes inversely with rein length, and (3) changes with elasticity of the reins. Eight riding horses trotted in hand at consistent speed in a straight line wearing a bit and bridle and three types of side reins (inelastic, stiff elastic, compliant elastic) were evaluated in random order at long, neutral, and short lengths. Strain gauge transducers (240 Hz) measured minimal, maximal and mean rein tension, rate of loading and impulse. The effects of rein type and length were evaluated using ANOVA with Bonferroni post hoc tests. Rein tension oscillated in a regular pattern with a peak during each diagonal stance phase. Within each rein type, minimal, maximal and mean tensions were higher with shorter reins. At neutral or short lengths, minimal tension increased and maximal tension decreased with elasticity of the reins. Short, inelastic reins had the highest maximal tension and rate of loading. Since the tension variables respond differently to rein elasticity at different lengths, it is recommended that a set of variables representing different aspects of rein tension should be reported.